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 A possession condition for a particular concept may actually make use of that concept. The possession condition for and does so. We can also expect to use relatively observational concepts in specifying the kind of experience that have to be mentioned in the possession conditions for relatively observational concepts. What we must avoid is mention of the concept in question as such within the content of the attitudes attributed to the thinker in the possession condition. Otherwise we would be presupposing possession of the concept in an account that was meant to elucidate its possession. In talking of what the thinker finds compelling, the possession conditions can also respect an insight of the later Wittgenstein: That to find her finds it natural to go on in new cases in applying the concept.
 Sometimes a family of concepts has this property: It is not possible to master any one of the members of the family without mastering the others. Two of the families that plausibly have this status are these: The family consisting of some simple concepts 0, 1, 2, . . . of the natural numbers and the corresponding concepts of numerical quantifiers there are 0 so-and-so, there is 1 so-and-so, . . . and the family consisting of the concepts; belief and desire. Such families have come to be known as local holism. A local holism does not prevent the individuation of a concept by its possession condition. Rather, it demands that all the concepts in the family be individuated simultaneously. So one would say something of this form: Belief and desire form the unique pair of concepts C1 and C2 such that for as thinker to posses them are to meet such-and-such condition involving the thinker, C1 and C2. For these and other possession conditions to individuate properly, it is necessary that there be some ranking of the concepts treated. The possession conditions for concepts higher in the ranking must presuppose only possession of concepts at the same or lower levels in the ranking.
 A possession conditions may in various ways make a thinkers possession of a particular concept dependent upon his relations to his environment. Many possession conditions will mention the links between a concept and the thinkers perceptual experience. Perceptual experience represents the world as a certain way. It is arguable that the only satisfactory explanation of what it is for perceptual experience to represent the world in a particular way must refer to the complex relations of the experience to the subjects environment. If this is so, then mention of such experiences in a possession condition will make possession of that concept dependent in part upon the environmental relations of the thinker. Burge (1979) has also argued from intuitions about particular examples that, even though the thinkers non-environmental properties and relations remain constant, the conceptual content of his mental state can vary if the thinkers social environment is varied. A possession condition that properly individuates such a concept must take into account the thinkers social relations, in particular his linguistic relations.
 Concepts have a normative dimension, a fact strongly emphasized by Kripke. For any judgement whose content involves a given concept, there is a correctness condition for that judgement, a condition that is dependent in part upon the identity of the concept. The normative character of concepts also extends into making the territory of a thinkers reasons for making judgements. A thinkers visual perception can give him good reason for judging That man is bald: It does not by itself give him good reason for judging Rostropovich ids bald, even if the man he sees is Rostropovich. All these normative connections must be explained by a theory of concepts one approach to these matters is to look to the possession condition for the concept, and consider how the referent of a concept is fixed from it, together with the world. One proposal is that the referent of the concept is that object or, property, or function, . . . which makes the practices of judgement and inference mentioned in the possession condition always lead to true judgements and truth-preserving inferences. This proposal would explain why certain reasons are necessity good reasons for judging given contents. Provided the possession condition permits us to say what it is about a thinkers previous judgements that masker it, the case that he is employing one concept rather than another, this proposal would also have another virtue. It would allow us to say how the correctness condition is determined for a judgement in which the concept is applied to newly encountered objects. The judgement is correct if the new object has the property that in fact makes the judgmental practices mentioned in the possession condition yield true judgements, or truth-preserving inferences.
 These manifesting dissimilations have occasioned the affiliated differences accorded within the distinction as associated with Leibniz, who declares that there are only two kinds of truths-truths of reason and truths of fact. The forms are all either explicit identities, i.e., of the form 'A' is 'A', 'AB' is 'B', etc., or they are reducible to this form by successively substituting equivalent terms. Leibniz dubs them truths of reason because the explicit identities are self-evident deducible truths, whereas the rest can be converted to such by purely rational operations. Because their denial involves a demonstrable contradiction, Leibniz also says that truths of reason rest on the principle of contradiction, or identity and that they are necessary [propositions, which are true of all possible words. Some examples are All equilateral rectangles are rectangles and All bachelors are unmarried: The first is already of the form 'AB' is 'B' and the latter can be reduced to this form by substituting unmarried man fort Bachelors. Other examples, or so Leibniz believes, are God exists and the truths of logic, arithmetic and geometry.
 Truths of fact, on the other hand, cannot be reduced to an identity and our only way of knowing them is empirically by reference to the facts of the empirical world. Likewise, since their denial does not involve a contradiction, their truth is merely contingent: They could have been otherwise and hold of the actual world, but not of every possible one. Some examples are Caesar crossed the Rubicon and Leibniz was born in Leipzig, as well as propositions expressing correct scientific generalizations. In Leibniz's view, truths of fact rest on the principle of sufficient reason, which states that nothing can be so unless there is a reason that it is so. This reason is that the actual world (by which he means the total collection of things past, present and future) is better than any other possible worlds and was therefore created by God.
 In defending the principle of sufficient reason, Leibniz runs into serious problems. He believes that in every true proposition, the concept of the predicate is contained in that of the subject. (This holds even for propositions like Caesar crossed the Rubicon: Leibniz thinks anyone who did not cross the Rubicon, would not have been Caesar). And this containment relationship! Which is eternal and unalterable even by God ~? Guarantees that every truth has a sufficient reason. If truths consists in concept containment, however, then it seems that all truths are analytic and hence necessary, and if they are all necessary, surely they are all truths of reason. Leibnitz responds that not every truth can be reduced to an identity in a finite number of steps, in some instances revealing the connexion between subject and predicate concepts would requite an infinite analysis. But while this may entail that we cannot prove such propositions as deductively manifested, it does not appear to show that the proposition could have been false. Intuitively, it seems a better ground for supposing that it is necessary truth of a special sort. A related question arises from the idea that truths of fact depend on Gods decision to creates the best of all possible worlds: If it is part of the concept of this world that it is best, now could its existence be other than necessary? Leibniz answers that its existence is only hypothetically necessary, i.e., it follows from Gods decision to create this world, but God had the power to decide otherwise. Yet God is necessarily good and non-deceiving, so how could he have decided to do anything else? Leibniz says much more about these masters, but it is not clear whether he offers any satisfactory solutions.
 Leibniz and others have thought of truths as a property of propositions, where the latter are conceived as things that may be expressed by, but are distinct from, linguistic items like statements. On another approach, truth is a property of linguistic entities, and the basis of necessary truth in convention. Thus A.J. Ayer, for example,. Argued that the only necessary truths are analytic statements and that the latter rest entirely on our commitment to use words in certain ways.
 The slogan the meaning of a statement is its method of verification expresses the empirical verifications theory of meaning. It is more than the general criterion of meaningfulness if and only if it is empirically verifiable. If says in addition what the meaning of a sentence is: It is all those observations that would confirm or disconfirmed the sentence. Sentences that would be verified or falsified by all the same observations are empirically equivalent or have the same meaning. A sentence is said to be cognitively meaningful if and only if it can be verified or falsified in experience. This is not meant to require that the sentence be conclusively verified or falsified, since universal scientific laws or hypotheses (which are supposed to pass the test) are not logically deducible from any amount of actually observed evidence.
 When one predicates necessary truth of a preposition one speaks of modality dedicto. For one ascribes the modal property, necessary truth, to a dictum, namely, whatever proposition is taken as necessary. A venerable tradition, however, distinguishes this from necessary de re, wherein one predicates necessary or essential possession of some property to an on object. For example, the statement '4' is necessarily greater than '2' might be used to predicate of the object, '4', the property, being necessarily greater than '2'. That objects have some of their properties necessarily, or essentially, and others only contingently, or accidentally, are a main part of the doctrine called; essentialism. Thus, an essentials might say that Socrates had the property of being bald accidentally, but that of being self-identical, or perhaps of being human, essentially. Although essentialism has been vigorously attacked in recent years, most particularly by Quine, it also has able contemporary proponents, such as Plantinga.
 Modal necessity as seen by many philosophers whom have traditionally held that every proposition has a modal status as well as a truth value. Every proposition is either necessary or contingent as well as either true or false. The issue of knowledge of the modal status of propositions has received much attention because of its intimate relationship to the issue of deductive reasoning. For example, no propositions of the theoretic content that all knowledge of necessary propositions is deductively knowledgeable. Others reject this claim by citing Kripkes (1980) alleged cases of necessary theoretical propositions. Such contentions are often inconclusive, for they fail to take into account the following tripartite distinction: 'S' knows the general modal status of 'p' just in case 'S' knows that 'p' is a necessary proposition or 'S' knows the truth that 'p' is a contingent proposition. 'S' knows the truth value of 'p' just in case 'S' knows that 'p' is true or 'S' knows that 'p' is false. 'S' knows the specific modal status of 'p' just in case 'S' knows that 'p' is necessarily true or 'S' knows that 'p' is necessarily false or 'S' knows that 'p' is contingently true or 'S' knows that 'p' is contingently false. It does not follow from the fact that knowledge of the general modal status of a proposition is a deductively reasoned distinctive modal status is also given to theoretical principles. Nor des it follow from the fact that knowledge of a specific modal status of a proposition is theoretically given as to the knowledge of its general modal status that also is deductive.
 The certainties involving reason and a truth of fact are much in distinction by associative measures given through Leibniz, who declares that there are only two kinds of truths-truths of reason and truths of fact. The former are all either explicit identities, i.e., of the form 'A' is 'A', 'AB' is 'B', etc., or they are reducible to this form by successively substituting equivalent terms. Leibniz dubs them truths of reason because the explicit identities are self-evident theoretical truth, whereas the rest can be converted to such by purely rational operations. Because their denial involves a demonstrable contradiction, Leibniz also says that truths of reason rest on the principle of contraction, or identity and that they are necessary propositions, which are true of all possible worlds. Some examples are that All bachelors are unmarried: The first is already of the form 'AB' is 'B' and the latter can be reduced to this form by substituting unmarried man for Bachelors. Other examples, or so Leibniz believes, are God exists and the truth of logic, arithmetic and geometry.
 Truths of fact, on the other hand, cannot be reduced to an identity and our only way of knowing hem os a theoretical manifestations, or by reference to the fact of the empirical world. Likewise, since their denial does not involve as contradiction, their truth is merely contingent: They could have been otherwise and hold of the actual world, but not of every possible one. Some examples are Caesar crossed the Rubicon and Leibniz was born in Leipzig, as well as propositions expressing correct scientific generalizations. In Leibniz's view, truths of fact rest on the principle of sufficient reason, which states that nothing can be so unless thee is a reason that it is so. This reason is that the actual world (by which he means the total collection of things past, present and future) is better than any other possible world and was therefore created by God.
 In defending the principle of sufficient reason, Leibniz runs into serious problems. He believes that in every true proposition, the concept of the predicate is contained in that of the subject. (This holds even for propositions like Caesar crossed the Rubicon: Leibniz thinks anyone who did not cross the Rubicon would not have been Caesar) And this containment relationship-that is eternal and unalterable even by God-guarantees that every truth has a sufficient reason. If truth consists in concept containment, however, then it seems that all truths are analytic and hence necessary, and if they are all necessary, surely they are all truths of reason. Leibniz responds that not evert truth can be reduced to an identity in a finite number of steps: In some instances revealing the connexion between subject and predicate concepts would require an infinite analysis. But while this may entail that we cannot prove such propositions as deductively probable, it does not appear to show that the proposition could have been false. Intuitively, it seems a better ground for supposing that it is a necessary truth of a special sort. A related question arises from the idea that truths of fact depend on Gods decision to create the best world, if it is part of the concept of this world that it is best, how could its existence be other than necessary? Leibniz answers that its existence is only hypothetically necessary, i.e., it follows from Gods decision to create this world, but God is necessarily good, so how could he have decided to do anything else? Leibniz says much more about the matters, but it is not clear whether he offers any satisfactory solutions.
 The modality of a proposition is the way in which it is true or false. The most important division is between propositions true of necessity, and those true as a things are: Necessary as opposed to contingent propositions. Other qualifiers sometimes called modal include the tense indicators It will be the case that 'p' or It was the case that 'p', and there are affinities between the deontic indicators, as it ought to be the case that 'p' or it is permissible that 'p', and the logical modalities as a logic that study the notions of necessity and possibility. Modal logic was of a great importance historically, particularly in the light of various doctrines concerning the necessary properties of the deity, but was not a central topic of modern logic in its golden period at the beginning of the 20th century. It was, however, revived by C. I. Lewis, by adding to a propositional or predicate calculus two operators, □ and ◊ (sometimes written N and M), meaning necessarily and possibly, respectively. These like p ➞ ◊ p and □ p ➞ p will be to include □ p ➞ □□ p , if a proposition is necessary, and ◊ p ➞ □ ◊ p, if a proposition is possible. The classical modal theory for modal logic, due to Kripke and the Swedish logician Stig Kanger, involves valuing propositions not as true or false simplicitiers, but as true or false art possible worlds, with necessity then corresponding to truth in all worlds, and possibly to truths in some world.
 The doctrine advocated by David Lewis, which different possible worlds are to be thought of as existing exactly as this one does. Thinking in terms of possibilities is thinking of real worlds where things are different, this view has been charged with misrepresenting it as some insurmountably unseeing to why it is good to save the child from drowning, since there is still a possible world in which she (or her counterpart) drowned, and from the standpoint of the universe it should make no difference that world is actual. Critics asio charge either that the notion fails to fit with a coherent theory of how we know about possible worlds, or with a coherent theory about possible worlds, or with a coherent theory of why we are interested in them, but Lewis denies that any other way of interpreting modal statements is tenable.
 Knowledge and belief, according to most epistemologists, knowledge entails belief, so that I cannot know that such and such is the case unless I believer that such and such is the case. Others think this entailment thesis can be rendered more accurately if we substitute for belief some closely related attitude. For instance, several philosophers would prefer to say that knowledge entail psychological certainties (Prichard, 1950 and Ayer, 1956) or conviction (Lehrer, 1974) or acceptance (Lehrer, 1989). None the less, there are arguments against all versions of the thesis that knowledge requires having a belief-like attitude toward the known. These arguments are given by philosophers who think that knowledge and belief (or a facsimile) are mutually incompatible (the incomparability thesis), or by ones who say that knowledge does not entail belief, or vice versa, so that each may exist without the other, but the two may also coexist (the separability thesis).
 The incompatibility thesis is sometimes traced to Plato, 429-347 Bc in view of his claim that knowledge is infallible while belief or opinion is fallible (Republic 476-9). But this claim would not support the thesis. Belief might be a component of an infallible form of knowledge in spite of the fallibility of belief. Perhaps, knowledge involves some factor that compensates for the fallibility of belief.
 A. Duncan-Jones (1939: Also Vendler, 1978) cite linguistic evidence to back up the incompatibility thesis. He notes that people often say I do not believer she is guilty. I know she is and the like, which suggest that belief rule out knowledge. However, as Lehrer (1974) indicates, the above exclamation is only a more emphatic way of saying I do not just believer she is guilty, I know she is where just makes it especially clear that the speaker is signalling that she has something more salient than mere belief, not that she has something inconsistent with belief, namely knowledge. Compare: You do not hurt him, you killed him.
 A. Prichard (1966) offers a defence of the incompatibility thesis that hinges on the equation of knowledge with certainty (both infallibility and psychological certitude) and the assumption that when we believer in the truth of a claim we are not certain about its truth. Given that belief always involves uncertainty while knowledge never dies, believing something rules out the possibility of knowing it. Unfortunately, however, Prichard gives us no goods reason to grant that states of belief are never ones involving confidence. Conscious beliefs clearly involve some level of confidence, to suggest that we cease to believer things about which we are completely confident is bizarre.
 A.D. Woozley (1953) defends a version of the separability thesis. Woozley's version, which deals with psychological certainty rather than belief per se, is that knowledge can exist in the absence of confidence about the item known, although might also be accompanied by confidence as well. Woozley remarks that the test of whether I know something is what I can do, where what I can do may include answering questions. On the basis of this remark he suggests that even when people are unsure of the truth of a claim, they might know that the claim is true. We unhesitatingly attribute knowledge to people who give correct responses on examinations even if those people show no confidence in their answers. Woozley acknowledges, however, that it would be odd for those who lack confidence to claim knowledge. It would be peculiar to say, I am unsure whether my answer is true: Still, I know it is correct. But this tension Woozley explains using a distinction between conditions under which we are justified in making a claim (such as a claim to know something), and conditions under which the claim we make is true. While I know such and such might be true even if I am unsure whether such and such holds, nonetheless it would be inappropriate for me to claim that I know that such and such unless I were sure of the truth of my claim.
 Colin Radford (1966) extends Woozley's defence of the separability thesis. In Radford's view, not only is knowledge compatible with the lack of certainty, it is also compatible with a complete lack of belief. He argues by example. In one example, Jean has forgotten that he learned some English history years priori and yet he is able to give several correct responses to questions such as When did the Battle of Hastings occur? Since he forgot that he took history, he considers the correct response to be no more than guesses. Thus, when he says that the Battle of Hastings took place in 1066 he would deny having the belief that the Battle of Hastings took place in 1066. A disposition he would deny being responsible (or having the right to be convincing) that 1066 was the correct date. Radford would none the less insist that Jean know when the Battle occurred, since clearly be remembering the correct date. Radford admits that it would be inappropriate for Jean to say that he knew when the Battle of Hastings occurred, but, like Woozley he attributes the impropriety to a fact about when it is and is not appropriate to claim knowledge. When we claim knowledge, we ought, at least to believer that we have the knowledge we claim, or else our behavior is intentionally misleading.
 Those that agree with Radford's defence of the separability thesis will probably think of belief as an inner state that can be detected through introspection. That Jean lacks beliefs about English history is plausible on this Cartesian picture since Jean does not find himself with any beliefs about English history when ne seek them out. One might criticize Radford, however, by rejecting that Cartesian view of belief. One could argue that some beliefs are thoroughly unconscious, for example. Or one could adopt a behaviourist conception of belief, such as Alexander Bains (1859), according to which having beliefs is a matter of the way people are disposed to behave (and has not Radford already adopted a behaviourist conception of knowledge?) Since Jean gives the correct response when queried, a form of verbal behavior, a behaviourist would be tempted to credit him with the belief that the Battle of Hastings occurred in 1066.
 D.M. Armstrong (1873) takes a different tack against Radford. Jean does know that the Battle of Hastings took place in 1066. Armstrong will grant Radfod that point, in fact, Armstrong suggests that Jean believer that 1066 is not the date the Battle of Hastings occurred, for Armstrong equates the belief that such and such is just possible but no more than just possible with the belief that such and such is not the case. However, Armstrong insists, Jean also believes that the Battle did occur in 1066. After all, had Jean been mistaught that the Battle occurred in 1066, and subsequently guessed that it took place in 1066, we would surely describe the situation as one in which Jeans false belief about the Battle became unconscious over time but persisted of a memory trace that was causally responsible for his guess. Out of consistency, we must describe Radford's original case as one that Jeans true belief became unconscious but persisted long enough to cause his guess. Thus, while Jean consciously believes that the Battle did not occur in 1066, unconsciously he does believer it occurred in 1066. So after all, Radford does not have a counterexample to the claim that knowledge entails belief.
 Armstrong's response to Radford was to reject Radford's claim that the examinee lacked the relevant belief about English history. Another response is to argue that the examinee lacks the knowledge Radford attributes to him (cf. Sorenson, 1982). If Armstrong is correct in suggesting that Jean believes both that 1066 is and that it is not the date of the Battle of Hastings, one might deny Jean knowledge on the grounds that people who believer the denial of what they believer cannot be said to' know the truth of their belief. Another strategy might be to compare the examine case with examples of ignorance given in recent attacks on externalist accounts of knowledge (needless to say.  Externalists themselves would tend not to favours this strategy). Consider the following case developed by BonJour (1985): For no apparent reason, Samantha believes that she is clairvoyant. Again, for no apparent reason, she one day comes to believer that the President is in New York City, even though she has every reason to believer that the President is in Washington, D.C. In fact, Samantha is a completely reliable clairvoyant, and she has arrived at her belief about the whereabouts of the President thorough the power of her clairvoyance. Yet surely Samanthas belief is completely irrational. She is not justified in thinking what she does. If so, then she does not know where the President is. But Radford's examinee is unconventional. Even if Jean lacks the belief that Radford denies him, Radford does not have an example of knowledge that is unattended with belief. Suppose that Jeans memory had been sufficiently powerful to produce the relevant belief. As Radford says, in having every reason to suppose that his response is mere guesswork, and he has every reason to consider his belief false. His belief would be an irrational one, and hence one about whose truth Jean would be ignorant.
 Least has been of mention to an approaching view from which perception basis upon itself as a fundamental philosophical topic both for its central place in a theory of knowledge, and its central place un any theory of consciousness. Philosophy in this area is constrained by a number of properties that we believer to hold of perception, (1) It gives us knowledge of the world around us. (2) We are conscious of that world by being aware of sensible qualities: Colour, sounds, tastes, smells, felt warmth, and the shapes and positions of objects in the environment. (3) Such consciousness is effected through highly complex information channels, such as the output of the three different types of colour-sensitive cells in the eye, or the channels in the ear for interpreting pulses of air pressure as frequencies of sound. (4) There ensues even more complex neurophysiological coding of that information, and eventually higher-order brain functions bring it about that we interpreted the information so received. (Much of this complexity has been revealed by the difficulties of writing programs enabling computers to recognize quite simple aspects of the visual scene.) The problem is to avoid thinking of here being a central, ghostly, conscious self, fed information in the same way that a screen if fed information by a remote television camera. Once such a model is in place, experience will seem like a veil getting between us and the world, and the direct objects of perception will seem to be private items in an inner theater or sensorium. The difficulty of avoiding this model is epically cute when we considered the secondary qualities of colour, sound, tactile feelings and taste, which can easily seem to have a purely private existence inside the perceiver, like sensation of pain. Calling such supposed items names like sense-data or percepts exacerbates the tendency, but once the model is in place, the first property, that perception gives us knowledge of the world and its surrounding surfaces, is quickly threatened, for there will now seem little connexion between these items in immediate experience and any independent reality. Reactions to this problem include scepticism and idealism.
 A more hopeful approach is to claim that the complexities of (3) and (4) explain how we can have direct acquaintance of the world, than suggesting that the acquaintance we do have been at best indirect. It is pointed out that perceptions are not like sensation, precisely because they have a content, or outer-directed nature. To have a perception is to be aware of the world for being such-and-such a way, than to enjoy a mere modification of sensation. But such direct realism has to be sustained in the face of the evident personal (neurophysiological and other) factors determining haw we perceive. One approach is to ask why it is useful to be conscious of what we perceive, when other aspects of our functioning work with information determining responses without any conscious awareness or intervention. A solution to this problem would offer the hope of making consciousness part of the natural world, than a strange optional extra.
 Furthering, perceptual knowledge is knowledge acquired by or through the senses and includes most of what we know. We cross intersections when we see the light turn green, head for the kitchen when we smell the roast burning, squeeze the fruit to determine its ripeness, and climb out of bed when we hear the alarm ring. In each case we come to know something-that the light has turned green, that the roast is burning, that the melon is overripe, and that it is time to get up-by some sensory means. Seeing that the light has turned green is learning something-that, the light has turned green-by use of the eyes. Feeling that the melon is overripe is coming to know a fact-that the melon is overripe-by ones sense to touch. In each case the resulting knowledge is somehow based on, derived from or grounded in the sort of experience that characterizes the sense modality in question.
 Much of our perceptual knowledge is indirect, dependent or derived. By this I mean that the facts we describe ourselves as learning, as coming to know, by perceptual means are pieces of knowledge that depend on our coming to know something else, some other fact, in a more direct way. We see, by the gauge, that we need gas, see, by the newspapers, that our team has lost again, see, by her expression, that she is nervous. This derived or dependent sort of knowledge is particularly prevalent in the cases of vision, but it occurs, to a lesser degree, in every sense modality. We install bells and other noise-makers so that we calm for example, hear (by the bell) that someone is at the door and (by the alarm) that its time to get up. When we obtain knowledge in this way, it is clear that unless one can see, hence, comes to know something about the gauge (that it says) and, hence, know that one is described as coming to know by perceptual means. If one cannot hear that the bell is ringing, one cannot-in at least in this way-hear that ones visitors have arrived. In such cases one sees (hears, smells, etc.) that 'a' is 'F', coming to know thereby that 'a' is 'F', by seeing (hearing, etc.) that some other condition, 'b's' being 'G', obtains when this occurs, the knowledge (that a is F) is derived from, or dependent on, the more basic perceptual knowledge that 'b' is 'G'.
 Perhaps as a better strategy is to tie an account save that part that evidence could justify explanation for it is its truth alone. Since, at least the time of Aristotle philosophers of explanatory knowledge have emphasizes of its importance that, in its simplest Termes, we want to know not only what are the composite peculiarities and particulars points of issue but also why it is. This consideration suggests that we define an explanation as an answer to a why-question. Such a definition would, however, be too broad, because some why-questions are requests for consolation (Why did my son have to die?) Or moral justification (Why should women not be paid the same as men for the same work?) It would also be too narrow because some explanations are responses to how-questions (How does radar work?) Or how-possibility-questions (How is it possible for cats always to land their feet?)
 In its overall sense, to explain means to make clear, to make plain, or to provide understanding. Definition of this sort are philosophically unhelpful, for the terms used in the deficient are no less problematic than the term to be defined. Moreover, since a wide variety of things require explanation, and since many different types of explanation exist, as more complex explanation is required. To facilitate the requirement leaves, least of mention, for us to consider by introduction a bit of technical terminology. The term explanation is used to refer to that which is to be explained: The term explanans refers to that which does the explaining, the explanans and the explanation taken together constitute the explanation.
 One common type of explanation occurs when deliberate human actions are explained in terms of conscious purposes. Why did you go to the pharmacy yesterday? Because I had a headache and needed to get some aspirin. It is tacitly assumed that aspirin is an appropriate medication for headaches and that going t the pharmacy would bean efficient way of getting some. Such explanations are, of course, teleological, referring, ss they do, to goals. The explanans is not the realisation of a future goal-if the pharmacy happened to be closed for stocktaking the aspirin would have ben obtained there, bu t that would not invalidate the explanation. Some philosophers would say that the antecedent desire to achieve the end is what doers the explaining: Others might say that the explaining is done by the nature of the goal and the fact that the action promoted the chances of realizing it. (Taylor, 1964). In that it should not be automatically be assumed that such explanations are causal. Philosophers differ considerably on whether these explanations are to be framed in terms of cause or reason, but the distinction cannot be used to show that the relation between reasons and the actions they justify is in no way causal, and there are many differing analyses of such concepts as intention and agency. Expanding the domain beyond consciousness, Freud maintained, in addition, that much human behavior can be explained in terms of unconscious and conscious wishes. Those Freudian explanations should probably be construed as basically causal.
 Problems arise when teleological explanations are offered in other context. The behavior of non-human animals is often explained in terms of purpose, e.g., the mouse ran to escape from the cat. In such cases the existence of conscious purpose seems dubious. The situation is still more problematic when a supra-empirical purpose in invoked -, e.g., the explanations of living species in terms of Gods purpose, or the vitalistic explanations of biological phenomena in terms of a entelechy or vital principle. In recent years an anthropic principle has received attention in cosmology (Barrow and Tipler, 1986). All such explanations have been concerned by many philosophers an anthropomorphic.
 Nevertheless, philosophers and scientists often maintain that functional explanations play an important an legitimate role in various sciences such as, evolutionary biology, anthropology and sociology. For example, of the peppered moth in Liverpool, the change in colour from the light phase to the dark phase and back again to the light phase provided adaption to a changing environment and fulfilled the function of reducing predation on the spacies. In the study of primitive soviets anthropologists have maintained that various rituals the (rain dance) which may be inefficacious in braining about their manifest Gaels (producing rain), actually cohesion at a period of stress (often a drought). Philosophers who admit teleological and/or functional explanations in common sense and science oftentimes take pans to argue that such explanations can be annualized entirely in terms of efficient causes, thereby escaping the charge of anthropomorphism (Wright, 1976): Again, however, not all philosophers agree.
 Mainly to avoid the incursion of unwanted theology, metaphysics, or anthropomorphism into science, many philosophers and scientists, especially during the first half of the twentieth century-held that science provides only descriptions and predictions of natural phenomena, but not explanations for a series of influential philosophers of science-including Karl Popper (1935) Carl Hempel and Paul Oppenheim (1948) and Hempel (1965)-maintained that empirical science can explain natural phenomena without appealing to metaphysics or theology. It appears that this view is now accepted by the vast majority of philosophers of science, though there is sharp disagreement on the nature of scientific explanation.
 Nevertheless, one important variety of reliability theory is a conclusive reason account, which includes a requirement that one’s reasons for believing that ‘h’ be such that in one’s circumstances, if h* were not to occur then, e.g., one would not have the reasons one does for believing that ‘h’, or, e.g., one would not believe that ‘h’. Roughly, the latter are demanded by theories that treat a Knower as ‘tracking the truth’, theories that include the further demand that is roughly, if it were the case, that ‘h’, then one would believe that ‘h’. A version of the tracking theory has been defended by Robert Nozick (1981), who adds that if what he calls a ‘method’ has been used to arrive at the belief that ‘h’, then the antecedent clauses of the two conditionals that characterize tracking will need to include the hypothesis that one would employ the very same method.
 But unless more conditions are added to Nozick’s analysis, it will be too weak to explain why one lack’s knowledge in a version of the last variant of the tricky Mr. Notgot case described above, where we add the following details: (a) Mr. Notgot’s compulsion is not easily changed, (b) while in the office, Mr. Notgot has no other easy trick of the relevant type to play on one) one arrives at one’s belief that ‘h’, not by reasoning through a false belief ut by basing belief that ‘h’, upon a true existential generalization of one’s evidence.
 Nozick’s analysis is in addition too strong to permit anyone ever to know that ‘h’: ‘Some of my beliefs about beliefs might be otherwise, e.g., I might have rejected on of them’. If I know that ‘h5' then satisfaction of the antecedent of one of Nozick’s conditionals would involve its being false that ‘h5', thereby thwarting satisfaction of the consequent’s requirement that I not then believe that ‘h5'. For the belief that ‘h5' is itself one of my beliefs about beliefs (Shope, 1984).
 Some philosophers think that the category of knowing for which true. Justified believing (accepting) is a requirement constituting only a species of Propositional knowledge, construed as an even broader category. They have proposed various examples of ‘PK’ that do not satisfy the belief and/ort justification conditions of the tripartite analysis. Such cases are often recognized by analyses of Propositional knowledge in terms of powers, capacities, or abilities. For instance, Alan R. White (1982) treats ‘PK’ as merely the ability to provide a correct answer to a possible questions, however, White may be equating ‘producing’ knowledge in the sense of producing ‘the correct answer to a possible question’ with ‘displaying’ knowledge in the sense of manifesting knowledge. (White, 1982). The latter can be done even by very young children and some non-human animals independently of their being asked questions, understanding questions, or recognizing answers to questions. Indeed, an example that has been proposed as an instance of knowing that ‘h’ without believing or accepting that ‘h’ can be modified so as to illustrate this point. Two examples concerns an imaginary person who has no special training or information about horses or racing, but who in an experiment persistently and correctly picks the winners of upcoming horseraces. If the example is modified so that the hypothetical ‘seer’ never picks winners but only muses over whether those horses wight win, or only reports those horses winning, this behaviour should be as much of a candidate for the person’s manifesting knowledge that the horse in question will win as would be the behaviour of picking it as a winner.
 These considerations expose limitations in Edward Craig’s analysis (1990) of the concept of knowing of a person’s being a satisfactory informant in relation to an inquirer who wants to find out whether or not ‘h’. Craig realizes that counterexamples to his analysis appear to be constituted by Knower who are too recalcitrant to inform the inquirer, or too incapacitate to inform, or too discredited to be worth considering (as with the boy who cried ‘Wolf’). Craig admits that this might make preferable some alternative view of knowledge as a different state that helps to explain the presence of the state of being a suitable informant when the latter does obtain. Such the alternate, which offers a recursive definition that concerns one’s having the power to proceed in a way representing the state of affairs, causally involved in one’s proceeding in this way. When combined with a suitable analysis of representing, this theory of propositional knowledge can be unified with a structurally similar analysis of knowing how to do something.
 Knowledge and belief, according to most epistemologists, knowledge entails belief, so that I cannot know that such and such is the case unless I believe that such and such is the case. Others think this entailment thesis can be rendered more accurately if we substitute for belief some closely related attitude. For instance, several philosophers would prefer to say that knowledge entail psychological certainties (Prichard, 1950 and Ayer, 1956) or conviction (Lehrer, 1974) or acceptance (Lehrer, 1989). None the less, there are arguments against all versions of the thesis that knowledge requires having a belief-like attitude toward the known. These arguments are given by philosophers who think that knowledge and belief (or a facsimile) are mutually incompatible (the incomparability thesis), or by ones who say that knowledge does not entail belief, or vice versa, so that each may exist without the other, but the two may also coexist (the separability thesis).
 The incompatibility thesis is sometimes traced to Plato ©. 429-347 BC) in view of his claim that knowledge is infallible while belief or opinion is fallible (‘Republic’ 476-9). But this claim would not support the thesis. Belief might be a component of an infallible form of knowledge in spite of the fallibility of belief. Perhaps, knowledge involves some factor that compensates for the fallibility of belief.
 A. Duncan-Jones (1939: Also Vendler, 1978) cite linguistic evidence to back up the incompatibility thesis. He notes that people often say ‘I do not believe she is guilty. I know she is’ and the like, which suggest that belief rule out knowledge. However, as Lehrer (1974) indicates, the above exclamation is only a more emphatic way of saying ‘I do not just believe she is guilty, I know she is’ where ‘just’ makes it especially clear that the speaker is signalling that she has something more salient than mere belief, not that she has something inconsistent with belief, namely knowledge. Compare: ‘You do not hurt him, you killed him’.
 H.A. Prichard (1966) offers a defence of the incompatibility thesis that hinges on the equation of knowledge with certainty (both infallibility and psychological certitude) and the assumption that when we believe in the truth of a claim we are not certain about its truth. Given that belief always involves uncertainty while knowledge never dies, believing something rules out the possibility of knowing it. Unfortunately, however, Prichard gives ‘us’ no goods reason to grant that states of belief are never ones involving confidence. Conscious beliefs clearly involve some level of confidence, to suggest that we cease to believe things about which we are completely confident is bizarre.
 A.D. Woozley (1953) defends a version of the separability thesis. Woozley’s version, which deals with psychological certainty rather than belief per se, is that knowledge can exist in the absence of confidence about the item known, although might also be accompanied by confidence as well. Woozley remarks that the test of whether I know something is ‘what I can do, where what I can do may include answering questions’. On the basis of this remark he suggests that even when people are unsure of the truth of a claim, they might know that the claim is true. We unhesitatingly attribute knowledge to people who give correct responses on examinations even if those people show no confidence in their answers. Woozley acknowledges, however, that it would be odd for those who lack confidence to claim knowledge. It would be peculiar to say, ‘I am unsure whether my answer is true: Still, I know it is correct’. But this tension Woozley explains using a distinction between conditions under which we are justified in making a claim (such as a claim to know something), and conditions under which the claim we make is true. While ‘I know such and such’ might be true even if I am unsure whether such and such holds, nonetheless it would be inappropriate for me to claim that I know that such and such unless I were sure of the truth of my claim.
 Colin Radford (1966) extends Woozley’s defence of the separability thesis. In Radford’s view, not only is knowledge compatible with the lack of certainty, it is also compatible with a complete lack of belief. He argues by example. In one example, Jean has forgotten that he learned some English history year’s priori and yet he is able to give several correct responses to questions such as ‘When did the Battle of Hastings occur’? Since he forgot that he took history, he considers the correct response to be no more than guesses. Thus, when he says that the Battle of Hastings took place in 1066 he would deny having the belief that the Battle of Hastings took place in 1066. A disposition he would deny being responsible (or having the right to be convincing) that 1066 was the correct date. Radford would none the less insist that Jean know when the Battle occurred, since clearly be remembering the correct date. Radford admits that it would be inappropriate for Jean to say that he knew when the Battle of Hastings occurred, but, like Woozley he attributes the impropriety to a fact about when it is and is not appropriate to claim knowledge. When we claim knowledge, we ought, at least to believe that we have the knowledge we claim, or else our behaviour is ‘intentionally misleading’.
 Those that agree with Radford’s defence of the separability thesis will probably think of belief as an inner state that can be detected through introspection. That Jean lack’s beliefs about English history is plausible on this Cartesian picture since Jean does not find himself with any beliefs about English history when ne seek them out. One might criticize Radford, however, by rejecting that Cartesian view of belief. One could argue that some beliefs are thoroughly unconscious, for example. Or one could adopt a behaviourist conception of belief, such as Alexander Bain’s (1859), according to which having beliefs is a matter of the way people are disposed to behave (and has not Radford already adopted a behaviourist conception of knowledge?) Since Jean gives the correct response when queried, a form of verbal behaviour, a behaviourist would be tempted to credit him with the belief that the Battle of Hastings occurred in 1066.
 D.M. Armstrong (1873) takes a different tack against Radford. Jean does know that the Battle of Hastings took place in 1066. Armstrong will grant Radfod that point, in fact, Armstrong suggests that Jean believe that 1066 is not the date the Battle of Hastings occurred, for Armstrong equates the belief that such and such is just possible but no more than just possible with the belief that such and such is not the case. However, Armstrong insists, Jean also believes that the Battle did occur in 1066. After all, had Jean been mistaught that the Battle occurred in 1066, and subsequently ‘guessed’ that it took place in 1066, we would surely describe the situation as one in which Jean’s false belief about the Battle became unconscious over time but persisted of a memory trace that was causally responsible for his guess. Out of consistency, we must describe Radford’s original case as one that Jean’s true belief became unconscious but persisted long enough to cause his guess. Thus, while Jean consciously believes that the Battle did not occur in 1066, unconsciously he does believe it occurred in 1066. So after all, Radford does not have a counterexample to the claim that knowledge entails belief.
 Armstrong’s response to Radford was to reject Radford’s claim that the examinee lacked the relevant belief about English history. Another response is to argue that the examinee lacks the knowledge Radford attributes to him (cf. Sorenson, 1982). If Armstrong is correct in suggesting that Jean believes both that 1066 is and that it is not the date of the Battle of Hastings, one might deny Jean knowledge on the grounds that people who believe the denial of what they believe cannot be said t know the truth of their belief. Another strategy might be to compare the examine case with examples of ignorance given in recent attacks on externalist accounts of knowledge (needless to say.  Externalists themselves would tend not to favour this strategy). Consider the following case developed by BonJour (1985): For no apparent reason, Samantha believes that she is clairvoyant. Again, for no apparent reason, she one day comes to believe that the President is in New York City, even though she has every reason to believe that the President is in Washington, D.C. In fact, Samantha is a completely reliable clairvoyant, and she has arrived at her belief about the whereabouts of the President thorough the power of her clairvoyance. Yet surely Samantha’s belief is completely irrational. She is not justified in thinking what she does. If so, then she does not know where the President is. But Radford’s examinee is unconventional. Even if Jean lacks the belief that Radford denies him, Radford does not have an example of knowledge that is unattended with belief. Suppose that Jean’s memory had been sufficiently powerful to produce the relevant belief. As Radford says, in having every reason to suppose that his response is mere guesswork, and he has every reason to consider his belief false. His belief would be an irrational one, and hence one about whose truth Jean would be ignorant.
 Least has been of mention to an approaching view from which ‘perception’ basis upon itself as a fundamental philosophical topic both for its central place in ant theory of knowledge, and its central place un any theory of consciousness. Philosophy in this area is constrained by a number of properties that we believe to hold of perception, (1) It gives ‘us’ knowledge of the world around ‘us’. (2) We are conscious of that world by being aware of ‘sensible qualities’: Colour, sounds, tastes, smells, felt warmth, and the shapes and positions of objects in the environment. (3) Such consciousness is effected through highly complex information channels, such as the output of the three different types of colour-sensitive cells in the eye, or the channels in the ear for interpreting pulses of air pressure as frequencies of sound. (4) There ensues even more complex neurophysiological coding of that information, and eventually higher-order brain functions bring it about that we interpreted the information so received. (Much of this complexity has been revealed by the difficulties of writing programs enabling computers to recognize quite simple aspects of the visual scene.) The problem is to avoid thinking of here being a central, ghostly, conscious self, fed information in the same way that a screen if fed information by a remote television camera. Once such a model is in place, experience will seem like a veil getting between ‘us’ and the world, and the direct objects of perception will seem to be private items in an inner theatre or sensorium. The difficulty of avoiding this model is epically cute when we considered the secondary qualities of colour, sound, tactile feelings and taste, which can easily seem to have a purely private existence inside the perceiver, like sensation of pain. Calling such supposed items names like ‘sense-data’ or ‘percepts’ exacerbates the tendency, but once the model is in place, the first property, that perception gives ‘us’ knowledge of the world and its surrounding surfaces, is quickly threatened, for there will now seem little connection between these items in immediate experience and any independent reality. Reactions to this problem include ‘scepticism’ and ‘idealism’.
 A more hopeful approach is to claim that the complexities of (3) and (4) explain how we can have direct acquaintance of the world, than suggesting that the acquaintance we do have been at best indirect. It is pointed out that perceptions are not like sensation, precisely because they have a content, or outer-directed nature. To have a perception is to be aware of the world for being such-and-such a way, than to enjoy a mere modification of sensation. But such direct realism has to be sustained in the face of the evident personal (neurophysiological and other) factors determining haw we perceive. One approach is to ask why it is useful to be conscious of what we perceive, when other aspects of our functioning work with information determining responses without any conscious awareness or intervention. A solution to this problem would offer the hope of making consciousness part of the natural world, than a strange optional extra.
 Furthering, perceptual knowledge is knowledge acquired by or through the senses and includes most of what we know. We cross intersections when we see the light turn green, head for the kitchen when we smell the roast burning, squeeze the fruit to determine its ripeness, and climb out of bed when we hear the alarm ring. In each case we come to know something-that the light has turned green, that the roast is burning, that the melon is overripe, and that it is time to get up-by some sensory means. Seeing that the light has turned green is learning something-that, the light has turned green-by use of the eyes. Feeling that the melon is overripe is coming to know a fact-that the melon is overripe-by one’s sense to touch. In each case the resulting knowledge is somehow based on, derived from or grounded in the sort of experience that characterizes the sense modality in question.
 Much of our perceptual knowledge is indirect, dependent or derived. By this I mean that the facts we describe ourselves as learning, as coming to know, by perceptual means are pieces of knowledge that depend on our coming to know something else, some other fact, in a more direct way. We see, by the gauge, that we need gas, see, by the newspapers, that our team has lost again, see, by her expression, that she is nervous. This derived or dependent sort of knowledge is particularly prevalent in the cases of vision, but it occurs, to a lesser degree, in every sense modality. We install bells and other noise-makers so that we calm for example, hear (by the bell) that someone is at the door and (by the alarm) that its time to get up. When we obtain knowledge in this way, it is clear that unless one sees-hence, comes to know something about the gauge (that it says) and (hence, know) that one is described as coming to know by perceptual means. If one cannot hear that the bell is ringing, one cannot-in at least in this way-hear that one’s visitors have arrived. In such cases one sees (hears, smells, etc.) that ‘a’ is ‘F’, coming to know thereby that ‘a’ is ‘F’, by seeing (hearing, etc.) that some other condition, ‘b’s’ being ‘G’, obtains when this occurs, the knowledge (that ‘a’ is ‘F’) is derived from, or dependent on, the more basic perceptual knowledge that ‘b’ is ‘G’.
 Perhaps as a better strategy is to tie an account save that part that evidence could justify explanation for it is its truth alone. Since, at least the time of Aristotle philosophers of explanatory knowledge have emphasizes of its importance that, in its simplest therms, we want to know not only what are the composite peculiarities and particulars points of issue but also why it is. This consideration suggests that we define an explanation as an answer to a why-question. Such a definition would, however, be too broad, because some why-questions are requests for consolation (Why did my son have to die?) Or moral justification (Why should women not be paid the same as men for the same work?) It would also be too narrow because some explanations are responses to how-questions (How does radar work?) Or how-possibility-questions (How is it possible for cats always to land their feet?)
 In its overall sense, ‘to explain’ means to make clear, to make plain, or to provide understanding. Definition of this sort are philosophically unhelpful, for the terms used in the deficient are no less problematic than the term to be defined. Moreover, since a wide variety of things require explanation, and since many different types of explanation exist, as more complex explanation is required. To facilitate the requirement leaves, least of mention, for us to consider by introduction a bit of technical terminology. The term ‘explanation’ is used to refer to that which is to be explained: The term ‘explanans’ refers to that which does the explaining, the explanans and the explanation taken together constitute the explanation.
 One common type of explanation occurs when deliberate human actions are explained in terms of conscious purposes. ‘Why did you go to the pharmacy yesterday?’ ‘Because I had a headache and needed to get some aspirin.’ It is tacitly assumed that aspirin is an appropriate medication for headaches and that going t the pharmacy would bean efficient way of getting some. Such explanations are, of course, teleological, referring, ss they do, to goals. The explanans is not the realisation of a future goal-if the pharmacy happened to be closed for stocktaking the aspirin would have ben obtained there, bu t that would not invalidate the explanation. Some philosophers would say that the antecedent desire to achieve the end is what doers the explaining: Others might say that the explaining is done by the nature of the goal and the fact that the action promoted the chances of realizing it. (Taylor, 1964). In that it should not be automatically be assumed that such explanations are causal. Philosophers differ considerably on whether these explanations are to be framed in terms of cause or reason, but the distinction cannot be used to show that the relation between reasons and the actions they justify is in no way causal, and there are many differing analyses of such concepts as intention and agency. Expanding the domain beyond consciousness, Freud maintained, in addition, that much human behaviour can be explained in terms of unconscious and conscious wishes. Those Freudian explanations should probably be construed as basically causal.
 Problems arise when teleological explanations are offered in other context. The behaviour of non-human animals is often explained in terms of purpose, e.g., the mouse ran to escape from the cat. In such cases the existence of conscious purpose seems dubious. The situation is still more problematic when a supr-empirical purpose in invoked -, e.g., the explanations of living species in terms of God’s purpose, or the vitalistic explanations of biological phenomena in terms of a entelechy or vital principle. In recent years an ‘anthropic principle’ has received attention in cosmology (Barrow and Tipler, 1986). All such explanations have been condemned by many philosophers an anthropomorphic.
 Nevertheless, philosophers and scientists often maintain that functional explanations play an important an legitimate role in various sciences such as, evolutionary biology, anthropology and sociology. For example, of the peppered moth in Liverpool, the change in colour from the light phase to the dark phase and back again to the light phase provided adaption to a changing environment and fulfilled the function of reducing predation on the spacies. In the study of primitive soviets anthropologists have maintained that various rituals the (rain dance) which may be inefficacious in braining about their manifest gaols (producing rain), actually cohesion at a period of stress (often a drought). Philosophers who admit teleological and/or functional explanations in common sense and science oftentimes take pans to argue that such explanations can be annualized entirely in terms of efficient causes, thereby escaping the charge of anthropomorphism (Wright, 1976): Again, however, not all philosophers agree.
 Mainly to avoid the incursion of unwanted theology, metaphysics, or anthropomorphism into science, many philosophers and scientists, especially during the first half of the twentieth century-held that science provides only descriptions and predictions of natural phenomena, but not explanations for a series of influential philosophers of science-including Karl Popper (1935) Carl Hempel and Paul Oppenheim (1948) and Hempel (1965)-maintained that empirical science can explain natural phenomena without appealing to metaphysics or theology. It appears that this view is now accepted by the vast majority of philosophers of science, though there is sharp disagreement on the nature of scientific explanation.
 The foregoing approach, developed by Hempel, Popper and others, became virtually a ‘received view’ in the 1960s and 1970s. According to this view, to give a scientific explanation of any natural phenomenon is to show how this phenomena can be subsumed under a law of nature. A particular repture in a water pipe can be explained by citing the universal law that water expands when it freezes and the fact that the temperature of water in a pipe dropped below the freezing point. General law, as well as particular facts, can be explained by subsumption, the law of conservation of linear momentum can be explained by derivation from Newton’s second and third laws of motion. Each of these explanations is a deductive argument: The explanans contains one or more statements of universal laws and, in many cases, statements deceiving initial conditions. This pattern of explanation is known as the deductive-nomological (D-N) model. Any such argument shows that the explanandun had to occur given the explanans.
 Many, though not all, adherents of the received view allow for explanation by subsumption under statistical laws. Hempel (1965) offers as an example the case of a man who recovered quickly from a streptococcus infection as a result of treatment with penicillin. Although not all strep infections’ clar up quickly under this treatment, the probability of recovery in such cases is high, and this is sufficient for legitimate explanation According to Hempel. This example conforms to the inductive-statistical (I-S) model. Such explanations are viewed as arguments, but they are inductive than deductive. In these instances the explanation confers high inductive probability on the explanandum. An explanation of a particular fact satisfying either the D-N or I-S model is an argument to the effect that the fact in question was to b e expected by virtue of the explanans.
 The received view been subjected to strenuous criticism by adherents of the causal/mechanical approach to scientific explanation (Salmon 1990). Many objections to the received view we engendered by he absence of caudal constraints (due largely to worries about Hume’s critique) on the N-D and I-S models. Beginning in the late 1950s, Michael Scriven advanced serious counter-examples to Hempel’s models: He was followed in the 1960s by Wesley Salmon and in the 1970s by Peter Railton. As accorded to the view, one explains phenomena identifying causes (a death is explained resalting from a massive cerebral haemorrhage) or by exposing underlying mechanisms (the behaviour of a gas is explained in terms of the motion of constituent molecules).
 A unification approach to explanation carries with the basic idea that we understand our world more adequately to the extent that we can reduce the number of independent assumptions we must introduce to account for what goes on in it. Accordingly, we understand phenomena to the degree that we can fit them into an overall world picture or Weltanschauung. In order to serve in scientific explanation, the world picture must be scientifically well founded.
 During the pas half-century much philosophical attention has ben focussed on explanation in science and in history. Considerable controversy has surrounded the question of whether historical explanation must be scientific, or whether history requires explanations of different types. Many diverse views have been articulated: The forgoing brief survey does not exhaust the variety (Salmon, 19990).
 In everyday life we encounter many types of explanation, which appear not to raise philosophical difficulties, in addition to those already made of mention. Prior to take-off a flight attendant explains how to use the safety equipment on the aero-plane. In a museum the guide explain the significance of a famous painting. A mathematics teacher explains a geometrical proof to a bewildered student. A newspaper story explains how a prisoner escaped. Additional examples come easily to mind, the main point is to remember the great variety of contexts in which explanations are sought and given into.
 Another item of importance to epistemology is the wider held notion that non-demonstrative inferences can be characterized as inference to the best explanation. Given the variety of views on the nature of explanation, this popular slogan can hardly provide a useful philosophical analysis
Early versions of defeasibility theories had difficulty allowing for the existence of evidence that was ‘merely misleading,’ as in the case where one does know that h3: ‘Tom Grabit stole a book from the library,’ thanks to having seen him steal it, yet where, unbeknown to oneself, Tom’s mother out of dementia gas testified that Tom was far away from the library at the time of the theft.  One’s justifiably believing that she gave the testimony would destroy one’s justification for believing that h3' if added by itself to one’s present evidence.
 At least some defeasibility theories cannot deal with the knowledge one has while dying that h4: ‘In this life there is no timer at which I believe that ‘d’, where the proposition that 'd' expresses the details regarding some philosophical matter, e.g., the maximum number of blades of grass ever simultaneously growing on the earth. When it just so happens that it is true that ‘d’, defeasibility analyses typically consider the addition to one’s dying thoughts of a belief that ‘d’ in such a way as to improperly rule out actual knowledge that ‘h4'.
 A quite different approach to knowledge, and one able to deal with some Gettier-type cases, involves developing some type of causal theory of Propositional knowledge. The interesting thesis that counts as a causal theory of justification (in the meaning of ‘causal theory’: Intended here) is the that of a belief is justified just in case it was produced by a type of process that is ‘globally’ reliable, that is, its propensity to produce true beliefs-that can be defined (to a god enough approximation) as the proportion of the bailiffs it produces (or would produce where it used as much as opportunity allows) that are true-is sufficiently meaningful-variations of this view have been advanced for both knowledge and justified belief. The first formulation of reliability account of knowing appeared in a note by F.P. Ramsey (1931), who said that a belief was knowledge if it is true, certain can obtain by a reliable process. P. Unger (1968) suggested that 'S’ knows that ‘p’ just in case it is not at all accidental that ‘S’ is right about its being the casse that ‘p’. D.M. Armstrong (1973) said that a non-inferential belief qualified as knowledge if the belief has properties that are nominally sufficient for its truth, i.e., guarantee its truth through and by the laws of nature.
 Such theories require that one or another specified relation hold that can be characterized by mention of some aspect of cassation concerning one’s belief that ‘h’ (or one’s acceptance of the proposition that ‘h’) and its relation to state of affairs ‘h*’, e.g., 'h' causes the belief: 'h' is causally sufficient for the belief 'h' and the belief have a common cause. Such simple versions of a causal theory are able to deal with the original Notgot case, since it involves no such causal relationship, but cannot explain why there is ignorance in the variants where Notgot and Berent Enç (1984) have pointed out that sometimes one knows of ‘χ’ that is ø thanks to recognizing a feature merely corelated with the presence of øness without endorsing a causal theory themselves, there suggest that it would need to be elaborated so as to allow that one’s belief that ‘χ’ has ø has been caused by a factor whose correlation with the presence of øness has caused in oneself, e.g., by evolutionary adaption in one’s ancestors, the disposition that one manifests in acquiring the belief in response to the correlated factor. Not only does this strain the unity of as causal theory by complicating it, but no causal theory without other shortcomings has been able to cover instances of deductively reasoned knowledge.
 Causal theories of Propositional knowledge differ over whether they deviate from the tripartite analysis by dropping the requirements that one’s believing (accepting) that ‘h’ be justified. The same variation occurs regarding reliability theories, which present the Knower as reliable concerning the issue of whether or not ‘h’, in the sense that some of one’s cognitive or epistemic states, θ, are such that, given further characteristics of oneself-possibly including relations to factors external to one and which one may not be aware-it is nomologically necessary (or at least probable) that ‘h’. In some versions, the reliability is required to be ‘global’ in as far as it must concern a nomologically (probabilistic) relationship) relationship of states of type θ to the acquisition of true beliefs about a wider range of issues than merely whether or not ‘h’. There is also controversy about how to delineate the limits of what constitutes a type of relevant personal state or characteristic. (For example, in a case where Mr. Notgot has not been shamming and one does know thereby that someone in the office owns a Ford, such as a way of forming beliefs about the properties of persons spatially close to one, or instead something narrower, such as a way of forming beliefs about Ford owners in offices partly upon the basis of their relevant testimony?)
 One important variety of reliability theory is a conclusive reason account, which includes a requirement that one’s reasons for believing that ‘h’ be such that in one’s circumstances, if h* were not to occur then, e.g., one would not have the reasons one does for believing that ‘h’, or, e.g., one would not believe that ‘h’. Roughly, the latter is demanded by theories that treat a Knower as ‘tracking the truth’, theories that include the further demand that is roughly, if it were the case, that ‘h’, then one would believe that ‘h’. A version of the tracking theory has been defended by Robert Nozick (1981), who adds that if what he calls a ‘method’ has been used to arrive at the belief that ‘h’, then the antecedent clauses of the two conditionals that characterize tracking will need to include the hypothesis that one would employ the very same method.
 But unless more conditions are added to Nozick’s analysis, it will be too weak to explain why one lack’s knowledge in a version of the last variant of the tricky Mr. Notgot case described above, where we add the following details: (a) Mr. Notgot’s compulsion is not easily changed, (b) while in the office, Mr. Notgot has no other easy trick of the relevant type to play on one, and finally for one’s belief that ‘h’, not by reasoning through a false belief ut by basing belief that ‘h’, upon a true existential generalization of one’s evidence.
 Nozick’s analysis is in addition too strong to permit anyone ever to know that ‘h’: ‘Some of my beliefs about beliefs might be otherwise, e.g., I might have rejected on of them’. If I know that ‘h5' then satisfaction of the antecedent of one of Nozick’s conditionals would involve its being false that ‘h5', thereby thwarting satisfaction of the consequent’s requirement that I not then believe that ‘h5'. For the belief that ‘h5' is itself one of my beliefs about beliefs (Shope, 1984).
 Some philosophers think that the category of knowing for which is true. Justified believing (accepting) is a requirement constituting only a species of Propositional knowledge, construed as an even broader category. They have proposed various examples of ‘PK’ that do not satisfy the belief and/ort justification conditions of the tripartite analysis. Such cases are often recognized by analyses of Propositional knowledge in terms of powers, capacities, or abilities. For instance, Alan R. White (1982) treats ‘PK’ as merely the ability to provide a correct answer to a possible questions, however, White may be equating ‘producing’ knowledge in the sense of producing ‘the correct answer to a possible question’ with ‘displaying’ knowledge in the sense of manifesting knowledge. (White, 1982). The latter can be done even by very young children and some non-human animals independently of their being asked questions, understanding questions, or recognizing answers to questions. Indeed, an example that has been proposed as an instance of knowing that ‘h’ without believing or accepting that ‘h’ can be modified so as to illustrate this point. Two examples concerns an imaginary person who has no special training or information about horses or racing, but who in an experiment persistently and correctly picks the winners of upcoming horseraces. If the example is modified so that the hypothetical ‘seer’ never picks winners but only muses over whether those horses wight win, or only reports those horses winning, this behaviour should be as much of a candidate for the person’s manifesting knowledge that the horse in question will win as would be the behaviour of picking it as a winner.
 These considerations expose limitations in Edward Craig’s analysis (1990) of the concept of knowing of a person’s being a satisfactory informant in relation to an inquirer who wants to find out whether or not ‘h’. Craig realizes that counterexamples to his analysis appear to be constituted by Knower who are too recalcitrant to inform the inquirer, or too incapacitate to inform, or too discredited to be worth considering (as with the boy who cried ‘Wolf’). Craig admits that this might make preferable some alternative view of knowledge as a different state that helps to explain the presence of the state of being a suitable informant when the latter does obtain. Such the alternate, which offers a recursive definition that concerns one’s having the power to proceed in a way representing the state of affairs, causally involved in one’s proceeding in this way. When combined with a suitable analysis of representing, this theory of propositional knowledge can be unified with a structurally similar analysis of knowing how to do something.
 Knowledge and belief, according to most epistemologists, knowledge entails belief, so that I cannot know that such and such is the case unless I believe that such and such is the case. Others think this entailment thesis can be rendered more accurately if we substitute for belief some closely related attitude. For instance, several philosophers would prefer to say that knowledge entail psychological certainties (Prichard, 1950 and Ayer, 1956) or conviction (Lehrer, 1974) or acceptance (Lehrer, 1989). None the less, there are arguments against all versions of the thesis that knowledge requires having a belief-like attitude toward the known. These arguments are given by philosophers who think that knowledge and belief (or a facsimile) are mutually incompatible (the incomparability thesis), or by ones who say that knowledge does not entail belief, or vice versa, so that each may exist without the other, but the two may also coexist (the separability thesis).
 The incompatibility thesis is sometimes traced to Plato (429-347 Bc) in view of his claim that knowledge is infallible while belief or opinion is fallible (‘Republic’ 476-9). But this claim would not support the thesis. Belief might be a component of an infallible form of knowledge in spite of the fallibility of belief. Perhaps, knowledge involves some factor that compensates for the fallibility of belief.
 A. Duncan-Jones (1939: Also Vendler, 1978) cite linguistic evidence to back up the incompatibility thesis. He notes that people often say ‘I do not believe she is guilty. I know she is’ and the like, which suggest that belief rule out knowledge. However, as Lehrer (1974) indicates, the above exclamation is only a more emphatic way of saying ‘I do not just believe she is guilty, I know she is’ where ‘just’ makes it especially clear that the speaker is signalling that she has something more salient than mere belief, not that she has something inconsistent with belief, namely knowledge. Compare: ‘You do not hurt him, you killed him.'
 H.A. Prichard (1966) offers a defence of the incompatibility thesis that hinges on the equation of knowledge with certainty (both infallibility and psychological certitude) and the assumption that when we believe in the truth of a claim we are not certain about its truth. Given that belief always involves uncertainty while knowledge never dies, believing something rules out the possibility of knowing it. Unfortunately, however, Prichard gives ‘us’ no goods reason to grant that states of belief are never ones involving confidence. Conscious beliefs clearly involve some level of confidence, to suggest that we cease to believe things about which we are completely confident is bizarre.
 A.D. Woozley (1953) defends a version of the separability thesis. Woozley’s version, which deals with psychological certainty rather than belief per se, is that knowledge can exist in the absence of confidence about the item known, although might also be accompanied by confidence as well. Woozley remarks that the test of whether I know something is ‘what I can do, where what I can do may include answering questions.’ On the basis of this remark he suggests that even when people are unsure of the truth of a claim, they might know that the claim is true. We unhesitatingly attribute knowledge to people who give correct responses on examinations even if those people show no confidence in their answers. Woozley acknowledges, however, that it would be odd for those who lack confidence to claim knowledge. It would be peculiar to say, I am unsure whether my answer is true: Still, I know it is correct But this tension Woozley explains using a distinction between conditions under which we are justified in making a claim (such as a claim to know something), and conditions under which the claim we make is true. While ‘I know such and such’ might be true even if I am unsure whether such and such holds, nonetheless it would be inappropriate for me to claim that I know that such and such unless I were sure of the truth of my claim.
 Colin Radford (1966) extends Woozley’s defence of the separability thesis. In Radford’s view, not only is knowledge compatible with the lack of certainty, it is also compatible with a complete lack of belief. He argues by example. In one example, Jean has forgotten that he learned some English history year’s priori and yet he is able to give several correct responses to questions such as ‘When did the Battle of Hastings occur?’ Since he forgot that he took history, he considers the correct response to be no more than guesses. Thus, when he says that the Battle of Hastings took place in 1066 he would deny having the belief that the Battle of Hastings took place in 1066. A disposition he would deny being responsible (or having the right to be convincing) that 1066 was the correct date. Radford would none the less insist that Jean know when the Battle occurred, since clearly be remembering the correct date. Radford admits that it would be inappropriate for Jean to say that he knew when the Battle of Hastings occurred, but, like Woozley he attributes the impropriety to a fact about when it is and is not appropriate to claim knowledge. When we claim knowledge, we ought, at least to believe that we have the knowledge we claim, or else our behaviour is ‘intentionally misleading’.
 Those that agree with Radford’s defence of the separability thesis will probably think of belief as an inner state that can be detected through introspection. That Jean lack’s beliefs about English history is plausible on this Cartesian picture since Jean does not find himself with any beliefs about English history when ne seek them out. One might criticize Radford, however, by rejecting that Cartesian view of belief. One could argue that some beliefs are thoroughly unconscious, for example. Or one could adopt a behaviourist conception of belief, such as Alexander Bain’s (1859), according to which having beliefs is a matter of the way people are disposed to behave (and has not Radford already adopted a behaviourist conception of knowledge?) Since Jean gives the correct response when queried, a form of verbal behaviour, a behaviourist would be tempted to credit him with the belief that the Battle of Hastings occurred in 1066.
 D.M. Armstrong (1873) takes a different tack against Radford. Jean does know that the Battle of Hastings took place in 1066. Armstrong will grant Radfod that point, in fact, Armstrong suggests that Jean believe that 1066 is not the date the Battle of Hastings occurred, for Armstrong equates the belief that such and such is just possible but no more than just possible with the belief that such and such is not the case. However, Armstrong insists, Jean also believes that the Battle did occur in 1066. After all, had Jean been mistaught that the Battle occurred in 1066, and subsequently ‘guessed’ that it took place in 1066, we would surely describe the situation as one in which Jean’s false belief about the Battle became unconscious over time but persisted of a memory trace that was causally responsible for his guess. Out of consistency, we must describe Radford’s original case as one that Jean’s true belief became unconscious but persisted long enough to cause his guess. Thus, while Jean consciously believes that the Battle did not occur in 1066, unconsciously he does believe it occurred in 1066. So after all, Radford does not have a counterexample to the claim that knowledge entails belief.
 Armstrong’s response to Radford was to reject Radford’s claim that the examinee lacked the relevant belief about English history. Another response is to argue that the examinee lacks the knowledge Radford attributes to him (cf. Sorenson, 1982). If Armstrong is correct in suggesting that Jean believes both that 1066 is and that it is not the date of the Battle of Hastings, one might deny Jean knowledge on the grounds that people who believe the denial of what they believe cannot be said t know the truth of their belief. Another strategy might be to compare the examine case with examples of ignorance given in recent attacks on externalist accounts of knowledge (needless to say.  Externalists themselves would tend not to favour this strategy). Consider the following case developed by BonJour (1985): For no apparent reason, Samantha believes that she is clairvoyant. Again, for no apparent reason, she one day comes to believe that the President is in New York City, even though she has every reason to believe that the President is in Washington, DC. In fact, Samantha is a completely reliable clairvoyant, and she has arrived at her belief about the whereabouts of the President thorough the power of her clairvoyance. Yet surely Samantha’s belief is completely irrational. She is not justified in thinking what she does. If so, then she does not know where the President is. But Radford’s examinee is unconventional. Even if Jean lacks the belief that Radford denies him, Radford does not have an example of knowledge that is unattended with belief. Suppose that Jean’s memory had been sufficiently powerful to produce the relevant belief. As Radford says, in having every reason to suppose that his response is mere guesswork, and he has every reason to consider his belief false. His belief would be an irrational one, and hence one about whose truth Jean would be ignorant.
 Least has been of mention to an approaching view from which ‘perception’ basis upon itself as a fundamental philosophical topic both for its central place in ant theory of knowledge, and its central place un any theory of consciousness. Philosophy in this area is constrained by a number of properties that we believe to hold of perception, (1) It gives ‘us’ knowledge of the world around ‘us,’ (2) We are conscious of that world by being aware of ‘sensible qualities’: Colour, sounds, tastes, smells, felt warmth, and the shapes and positions of objects in the environment. (3) Such consciousness is effected through highly complex information channels, such as the output of the three different types of colour-sensitive cells in the eye, or the channels in the ear for interpreting pulses of air pressure as frequencies of sound. (4) There ensues even more complex neurophysiological coding of that information, and eventually higher-order brain functions bring it about that we interpreted the information so received. (Much of this complexity has been revealed by the difficulties of writing programs enabling computers to recognize quite simple aspects of the visual scene.) The problem is to avoid thinking of here being a central, ghostly, conscious self, fed information in the same way that a screen if fed information by a remote television camera. Once such a model is in place, experience will seem like a veil getting between ‘us’ and the world, and the direct objects of perception will seem to be private items in an inner theatre or sensorium. The difficulty of avoiding this model is epically cute when we considered the secondary qualities of colour, sound, tactile feelings and taste, which can easily seem to have a purely private existence inside the perceiver, like sensation of pain. Calling such supposed items names like ‘sense-data’ or ‘percepts’ exacerbates the tendency, but once the model is in place, the first property, that perception gives ‘us’ knowledge of the world and its surrounding surfaces, is quickly threatened, for there will now seem little connection between these items in immediate experience and any independent reality. Reactions to this problem include ‘scepticism’ and ‘idealism.’
 A more hopeful approach is to claim that the complexities of (3) and (4) explain how we can have direct acquaintance of the world, than suggesting that the acquaintance we do have been at best indirect. It is pointed out that perceptions are not like sensation, precisely because they have a content, or outer-directed nature. To have a perception is to be aware of the world for being such-and-such a way, than to enjoy a mere modification of sensation. But such direct realism has to be sustained in the face of the evident personal (neurophysiological and other) factors determining haw we perceive. One approach is to ask why it is useful to be conscious of what we perceive, when other aspects of our functioning work with information determining responses without any conscious awareness or intervention. A solution to this problem would offer the hope of making consciousness part of the natural world, than a strange optional extra.
 Furthering, perceptual knowledge is knowledge acquired by or through the senses and includes most of what we know. We cross intersections when we see the light turn green, head for the kitchen when we smell the roast burning, squeeze the fruit to determine its ripeness, and climb out of bed when we hear the alarm ring. In each case we come to know something-that the light has turned green, that the roast is burning, that the melon is overripe, and that it is time to get up-by some sensory means. Seeing that the light has turned green is learning something-that the light has turned green-by use of the eyes. Feeling that the melon is overripe is coming to know a fact-that the melon is overripe-by one’s sense to touch. In each case the resulting knowledge is somehow based on, derived from or grounded in the sort of experience that characterizes the sense modality in question.
 Much of our perceptual knowledge is indirect, dependent or derived. By this I mean that the facts we describe ourselves as learning, as coming to know, by perceptual means are pieces of knowledge that depend on our coming to know something else, some other fact, in a more direct way. We see, by the gauge, that we need gas, see, by the newspapers, that our team has lost again, see, by her expression, that she is nervous. This derived or dependent sort of knowledge is particularly prevalent in the cases of vision, but it occurs, to a lesser degree, in every sense modality. We install bells and other noise-makers so that we calm for example, hear (by the bell) that someone is at the door and (by the alarm) that its time to get up. When we obtain knowledge in this way, it is clear that unless one sees-hence, comes to know something about the gauge (that it says) and (hence, know) that one is described as coming to know by perceptual means. If one cannot hear that the bell is ringing, one cannot-in at least in this way-hear that one’s visitors have arrived. In such cases one sees (hears, smells, etc.) that ‘a’ is ‘F’, coming to know thereby that ‘a’ is ‘F’, by seeing (hearing, etc.) that some other condition, ‘b’s’ being ‘G’, obtains when this occurs, the knowledge (that ‘a’ is ‘F’) is derived from, or dependent on, the more basic perceptual knowledge that ‘b’ is ‘G’.
 And finally, the representational Theory of mind (RTM) (which goes back at least to Aristotle) takes as its starting point commonsense mental states, such as thoughts, beliefs, desires, perceptions and images. Such states are said to have ‘intentionality’-they are about or refer to things, and may be evaluated with respect to properties like consistency, truth, appropriateness and accuracy. (For example, the thought that cousins are not related is inconsistent, the belief that Elvis is dead is true, the desire to eat the moon is inappropriate, a visual experience of a ripe strawberry as red is accurate, an image of George W. Bush with deadlocks is inaccurate.)
 The Representational Theory of Mind, defines such intentional mental states as relations to mental representations, and explains the intentionality of the former in terms of the semantic properties of the latter. For example, to believe that Elvis is dead is to be appropriately related to a mental representation whose propositional content is that Elvis is dead. (The desire that Elvis be dead, the fear that he is dead, the regret that he is dead, etc., involve different relations to the same mental representation.) To perceive a strawberry is to have a sensory experience of some kind which is appropriately related to (e.g., caused by) the strawberry Representational theory of mind also understands mental processes such as thinking, reasoning and imagining as sequences of intentional mental states. For example, to imagine the moon rising over a mountain is to entertain a series of mental images of the moon (and a mountain). To infer a proposition q from the propositions p and if 'p' then 'q' is (among other things) to have a sequence of thoughts of the form 'p', 'if p' then 'q', 'q'.
 Contemporary philosophers of mind have typically supposed (or at least hoped) that the mind can be naturalized-i.e., that all mental facts have explanations in the terms of natural science. This assumption is shared within cognitive science, which attempts to provide accounts of mental states and processes in terms (ultimately) of features of the brain and central nervous system. In the course of doing so, the various sub-disciplines of cognitive science (including cognitive and computational psychology and cognitive and computational neuroscience) postulate a number of different kinds of structures and processes, many of which are not directly implicated by mental states and processes as commonsensical conceived. There remains, however, a shared commitment to the idea that mental states and processes are to be explained in terms of mental representations.
 In philosophy, recent debates about mental representation have centred around the existence of propositional attitudes (beliefs, desires, etc.) and the determination of their contents (how they come to be about what they are about), and the existence of phenomenal properties and their relation to the content of thought and perceptual experience. Within cognitive science itself, the philosophically relevant debates have been focussed on the computational architecture of the brain and central nervous system, and the compatibility of scientific and commonsense accounts of mentality.
 Intentional Realists such as Dretske (e.g., 1988) and Fodor (e.g., 1987) note that the generalizations we apply in everyday life in predicting and explaining each other's behaviour (often collectively referred to as ‘folk psychology’) are both remarkably successful and indispensable. What a person believes, doubts, desires, fears, etc. is a highly reliable indicator of what that person will do; and we have no other way of making sense of each other's behaviour than by ascribing such states and applying the relevant generalizations. We are thus committed to the basic truth of commonsense psychology and, hence, to the existence of the states its generalizations refer to. (Some realists, such as Fodor, also hold that commonsense psychology will be vindicated by cognitive science, given that propositional attitudes can be construed as computational relations to mental representations.)
 Intentional Eliminativists, such as Churchland, (perhaps) Dennett and (at one time) Stich argue that no such things as propositional attitudes (and their constituent representational states) are implicated by the successful explanation and prediction of our mental lives and behaviour. Churchland denies that the generalizations of commonsense propositional-attitude psychology are true. He (1981) argues that folk psychology is a theory of the mind with a long history of failure and decline, and that it resists incorporation into the framework of modern scientific theories (including cognitive psychology). As such, it is comparable to alchemy and phlogiston theory, and ought to suffer a comparable fate. Commonsense psychology is false, and the states (and representations) it postulates simply don't exist. (It should be noted that Churchland is not an eliminativist about mental representation tout court.
 Dennett (1987) grants that the generalizations of commonsense psychology are true and indispensable, but denies that this is sufficient reason to believe in the entities they appear to refer to. He argues that to give an intentional explanation of a system's behaviour is merely to adopt the ‘intentional stance’ toward it. If the strategy of assigning contentful states to a system and predicting and explaining its behaviour (on the assumption that it is rational-i.e., that it behaves as it should, given the propositional attitudes it should have in its environment) is successful, then the system is intentional, and the propositional-attitude generalizations we apply to it are true. But there is nothing more to having a propositional attitude than this.
 Though he has been taken to be thus claiming that intentional explanations should be construed instrumentally, Dennett (1991) insists that he is a ‘moderate’ realist about propositional attitudes, since he believes that the patterns in the behaviour and behavioural dispositions of a system on the basis of which we (truly) attribute intentional states to it are objectively real. In the event that there are two or more explanatorily adequate but substantially different systems of intentional ascriptions to an individual, however, Dennett claims there is no fact of the matter about what the system believes (1987, 1991). This does suggest an irrealism at least with respect to the sorts of things Fodor and Dretske take beliefs to be; though it is not the view that there is simply nothing in the world that makes intentional explanations true.
 (Davidson 1973, 1974 and Lewis 1974 also defend the view that what it is to have a propositional attitude is just to be interpretable in a particular way. It is, however, not entirely clear whether they intend their views to imply irrealism about propositional attitudes.). Stich (1983) argues that cognitive psychology does not (or, in any case, should not) taxonomize mental states by their semantic properties at all, since attribution of psychological states by content is sensitive to factors that render it problematic in the context of a scientific psychology. Cognitive psychology seeks causal explanations of behaviour and cognition, and the causal powers of a mental state are determined by its intrinsic ‘structural’ or ‘syntactic’ properties. The semantic properties of a mental state, however, are determined by its extrinsic properties-e.g., its history, environmental or intra-mental relations. Hence, such properties cannot figure in causal-scientific explanations of behaviour. (Fodor 1994 and Dretske 1988 are realist attempts to come to grips with some of these problems.) Stich proposes a syntactic theory of the mind, on which the semantic properties of mental states play no explanatory role.
 It is a traditional assumption among realists about mental representations that representational states come in two basic varieties (Boghossian 1995). There are those, such as thoughts, which are composed of concepts and have no phenomenal (‘what-it's-like’) features (‘qualia’), and those, such as sensory experiences, which have phenomenal features but no conceptual constituents. (Non-conceptual content is usually defined as a kind of content that states of a creature lacking concepts might nonetheless enjoy. On this taxonomy, mental states can represent either in a way analogous to expressions of natural languages or in a way analogous to drawings, paintings, maps or photographs. (Perceptual states such as seeing that something is blue, are sometimes thought of as hybrid states, consisting of, for example, a Non-conceptual sensory experience and a thought, or some more integrated compound of sensory and conceptual components.)
 Some historical discussions of the representational properties of mind (e.g., Aristotle 1984, Locke 1689/1975, Hume 1739/1978) seem to assume that Non-conceptual representations-percepts (‘impressions’), images (‘ideas’) and the like-are the only kinds of mental representations, and that the mind represents the world in virtue of being in states that resemble things in it. On such a view, all representational states have their content in virtue of their phenomenal features. Powerful arguments, however, focussing on the lack of generality (Berkeley 1975), ambiguity (Wittgenstein 1953) and non-compositionality (Fodor 1981) of sensory and imagistic representations, as well as their unsuitability to function as logical (Frége 1918/1997, Geach 1957) or mathematical (Frége 1884/1953) concepts, and the symmetry of resemblance (Goodman 1976), convinced philosophers that no theory of mind can get by with only Non-conceptual representations construed in this way.
 Contemporary disagreement over Non-conceptual representation concerns the existence and nature of phenomenal properties and the role they play in determining the content of sensory experience. Dennett (1988), for example, denies that there are such things as qualia at all; while Brandom (2002), McDowell (1994), Rey (1991) and Sellars (1956) deny that they are needed to explain the content of sensory experience. Among those who accept that experiences have phenomenal content, some (Dretske, Lycan, Tye) argue that it is reducible to a kind of intentional content, while others (Block, Loar, Peacocke) argue that it is irreducible.
 There has also been dissent from the traditional claim that conceptual representations (thoughts, beliefs) lack phenomenology. Chalmers (1996), Flanagan (1992), Goldman (1993), Horgan and Tiensen (2003), Jackendoff (1987), Levine (1993, 1995, 2001), McGinn (1991), Pitt (2004), Searle (1992), Siewert (1998) and Strawson (1994), claim that purely symbolic (conscious) representational states themselves have a (perhaps proprietary) phenomenology. If this claim is correct, the question of what role phenomenology plays in the determination of content reprises for conceptual representation; and the eliminativist ambitions of Sellars, Brandom, Rey, would meet a new obstacle. (It would also raise prima face problems for reductivist representationalism
 The representationalist thesis is often formulated as the claim that phenomenal properties are representational or intentional. However, this formulation is ambiguous between a reductive and a non-deductive claim (though the term ‘representationalism’ is most often used for the reductive claim). On one hand, it could mean that the phenomenal content of an experience is a kind of intentional content (the properties it represents). On the other, it could mean that the (irreducible) phenomenal properties of an experience determine an intentional content. Representationalists such as Dretske, Lycan and Tye would assent to the former claim, whereas phenomenalists such as Block, Chalmers, Loar and Peacocke would assent to the latter. (Among phenomenalists, there is further disagreement about whether qualia are intrinsically representational (Loar) or not (Block, Peacocke).
 Most (reductive) representationalists are motivated by the conviction that one or another naturalistic explanation of intentionality is, in broad outline, correct, and by the desire to complete the naturalization of the mental by applying such theories to the problem of phenomenality. (Needless to say, most phenomenalists (Chalmers is the major exception) are just as eager to naturalize the phenomenal-though not in the same way.)
 The main argument for representationalism appeals to the transparency of experience (cf. Tye 2000: 45-51). The properties that characterize what it's like to have a perceptual experience are presented in experience as properties of objects perceived: in attending to an experience, one seems to ‘see through it’ to the objects and properties it is experiences of. They are not presented as properties of the experience itself. If nonetheless they were properties of the experience, perception would be massively deceptive. But perception is not massively deceptive. According to the representationalist, the phenomenal character of an experience is due to its representing objective, non-experiential properties. (In veridical perception, these properties are locally instantiated; in illusion and hallucination, they are not.) On this view, introspection is indirect perception: one comes to know what phenomenal features one's experience has by coming to know what objective features it represents.
 In order to account for the intuitive differences between conceptual and sensory representations, representationalists appeal to their structural or functional differences. Dretske (1995), for example, distinguishes experiences and thoughts on the basis of the origin and nature of their functions: an experience of a property 'P' is a state of a system whose evolved function is to indicate the presence of 'P' in the environment; a thought representing the property 'P', on the other hand, is a state of a system whose assigned (learned) function is to calibrate the output of the experiential system. Rey (1991) takes both thoughts and experiences to be relations to sentences in the language of thought, and distinguishes them on the basis of (the functional roles of) such sentences' constituent predicates. Lycan (1987, 1996) distinguishes them in terms of their functional-computational profiles. Tye (2000) distinguishes them in terms of their functional roles and the intrinsic structure of their vehicles: thoughts are representations in a language-like medium, whereas experiences are image-like representations consisting of ‘symbol-filled arrays.’ (the account of mental images in Tye 1991.)
 Phenomenalists tend to make use of the same sorts of features (function, intrinsic structure) in explaining some of the intuitive differences between thoughts and experiences; but they do not suppose that such features exhaust the differences between phenomenal and non-phenomenal representations. For the phenomenalism, it is the phenomenal properties of experiences-qualia themselves-that constitute the fundamental difference between experience and thought. Peacocke (1992), for example, develops the notion of a perceptual ‘scenario’ (an assignment of phenomenal properties to coordinates of a three-dimensional egocentric space), whose content is ‘correct’ (a semantic property) if in the corresponding ‘scene’ (the portion of the external world represented by the scenario) properties are distributed as their phenomenal analogues are in the scenario.
 Another sort of representation championed by phenomenalists (e.g., Block, Chalmers (2003) and Loar (1996)) is the ‘phenomenal concept’-a conceptual/phenomenal hybrid consisting of a phenomenological ‘sample’ (an image or an occurrent sensation) integrated with (or functioning as) a conceptual component. Phenomenal concepts are postulated to account for the apparent fact (among others) that, as McGinn (1991) puts it, ‘you cannot form [introspective] concepts of conscious properties unless you yourself instantiate those properties.’ One cannot have a phenomenal concept of a phenomenal property 'P', and, hence, phenomenal beliefs about P, without having experience of 'P', because 'P' itself is (in some way) constitutive of the concept of 'P'. (Jackson 1982, 1986 and Nagel 1974.)
 Though imagery has played an important role in the history of philosophy of mind, the important contemporary literature on it is primarily psychological. In a series of psychological experiments done in the 1970s (summarized in Kosslyn 1980 and Shepard and Cooper 1982), subjects' response time in tasks involving mental manipulation and examination of presented figures was found to vary in proportion to the spatial properties (size, orientation, etc.) of the figures presented. The question of how these experimental results are to be explained has kindled a lively debate on the nature of imagery and imagination.
 Kosslyn (1980) claims that the results suggest that the tasks were accomplished via the examination and manipulation of mental representations that themselves have spatial properties-i.e., pictorial representations, or images. Others, principally Pylyshyn (1979, 1981, 2003), argue that the empirical facts can be explained in terms exclusively of discursive, or propositional representations and cognitive processes defined over them. (Pylyshyn takes such representations to be sentences in a language of thought.)
 The idea that pictorial representations are literally pictures in the head is not taken seriously by proponents of the pictorial view of imagery The claim is, rather, that mental images represent in a way that is relevantly like the way pictures represent. (Attention has been focussed on visual imagery-hence the designation ‘pictorial’; though of course there may imagery in other modalities-auditory, olfactory, etc.-as well.)
 The distinction between pictorial and discursive representation can be characterized in terms of the distinction between analog and digital representation (Goodman 1976). This distinction has itself been variously understood (Fodor & Pylyshyn 1981, Goodman 1976, Haugeland 1981, Lewis 1971, McGinn 1989), though a widely accepted construal is that analog representation is continuous (i.e., in virtue of continuously variable properties of the representation), while digital representation is discrete (i.e., in virtue of properties a representation either has or doesn't have) (Dretske 1981). (An analog/digital distinction may also be made with respect to cognitive processes. (Block 1983.)) On this understanding of the analog/digital distinction, imagistic representations, which represent in virtue of properties that may vary continuously (such as being more or less bright, loud, vivid, etc.), would be analog, while conceptual representations, whose properties do not vary continuously (a thought cannot be more or less about Elvis: either it is or it is not) would be digital.
 It might be supposed that the pictorial/discursive distinction is best made in terms of the phenomenal/nonphenomenal distinction, but it is not obvious that this is the case. For one thing, there may be nonphenomenal properties of representations that vary continuously. Moreover, there are ways of understanding pictorial representation that presuppose neither phenomenality nor analogicity. According to Kosslyn (1980, 1982, 1983), a mental representation is ‘quasi-pictorial’ when every part of the representation corresponds to a part of the object represented, and relative distances between parts of the object represented are preserved among the parts of the representation. But distances between parts of a representation can be defined functionally rather than spatially-for example, in terms of the number of discrete computational steps required to combine stored information about them. (Rey 1981.)
 Tye (1991) proposes a view of images on which they are hybrid representations, consisting both of pictorial and discursive elements. On Tye's account, images are ‘(labelled) interpreted symbol-filled arrays.’ The symbols represent discursively, while their arrangement in arrays has representational significance (the location of each ‘cell’ in the array represents a specific viewer-centred 2-D location on the surface of the imagined object)
 The contents of mental representations are typically taken to be abstract objects (properties, relations, propositions, sets, etc.). A pressing question, especially for the naturalist, is how mental representations come to have their contents. Here the issue is not how to naturalize content (abstract objects can't be naturalized), but, rather, how to provide a naturalistic account of the content-determining relations between mental representations and the abstract objects they express. There are two basic types of contemporary naturalistic theories of content-determination, causal-informational and functional.
 Causal-informational theories (Dretske 1981, 1988, 1995) hold that the content of a mental representation is grounded in the information it carries about what does (Devitt 1996) or would (Fodor 1987, 1990) cause it to occur. There is, however, widespread agreement that causal-informational relations are not sufficient to determine the content of mental representations. Such relations are common, but representation is not. Tree trunks, smoke, thermostats and ringing telephones carry information about what they are causally related to, but they do not represent (in the relevant sense) what they carry information about. Further, a representation can be caused by something it does not represent, and can represent something that has not caused it.
 The main attempts to specify what makes a causal-informational state a mental representation are Asymmetric Dependency Theories (e.g., Fodor 1987, 1990, 1994) and Teleological Theories (Fodor 1990, Millikan 1984, Papineau 1987, Dretske 1988, 1995). The Asymmetric Dependency Theory distinguishes merely informational relations from representational relations on the basis of their higher-order relations to each other: informational relations depend upon representational relations, but not vice-versa. For example, if tokens of a mental state type are reliably caused by horses, cows-on-dark-nights, zebras-in-the-mist and Great Danes, then they carry information about horses, etc. If, however, such tokens are caused by cows-on-dark-nights, etc. because they were caused by horses, but not vice versa, then they represent horses.
 According to Teleological Theories, representational relations are those a representation-producing mechanism has the selected (by evolution or learning) function of establishing. For example, zebra-caused horse-representations do not mean zebra, because the mechanism by which such tokens are produced has the selected function of indicating horses, not zebras. The horse-representation-producing mechanism that responds to zebras is malfunctioning.
 Functional theories (Block 1986, Harman 1973), hold that the content of a mental representation is grounded in its (causal computational, inferential) relations to other mental representations. They differ on whether relata should include all other mental representations or only some of them, and on whether to include external states of affairs. The view that the content of a mental representation is determined by its inferential/computational relations with all other representations is holism; the view it is determined by relations to only some other mental states is localism (or molecularism). (The view that the content of a mental state depends on none of its relations to other mental states is atomism.) Functional theories that recognize no content-determining external relata have been called solipsistic (Harman 1987). Some theorists posit distinct roles for internal and external connections, the former determining semantic properties analogous to sense, the latter determining semantic properties analogous to reference (McGinn 1982, Sterelny 1989)
 (Reductive) representationalists (Dretske, Lycan, Tye) usually take one or another of these theories to provide an explanation of the (Non-conceptual) content of experiential states. They thus tend to be Externalists about phenomenological as well as conceptual content. Phenomenalists and non-deductive representationalists (Block, Chalmers, Loar, Peacocke, Siewert), on the other hand, take it that the representational content of such states is (at least in part) determined by their intrinsic phenomenal properties. Further, those who advocate a phenomenology-based approach to conceptual content (Horgan and Tiensen, Loar, Pitt, Searle, Siewert) also seem to be committed to internalist individuation of the content (if not the reference) of such states.
 Generally, those who, like informational theorists, think relations to one's (natural or social) environment are (at least partially) determinative of the content of mental representations are Externalists (e.g., Burge 1979, 1986, McGinn 1977, Putnam 1975), whereas those who, like some proponents of functional theories, think representational content is determined by an individual's intrinsic properties alone, are internalists (or individualists; cf. Putnam 1975, Fodor 1981)
 This issue is widely taken to be of central importance, since psychological explanation, whether commonsense or scientific, is supposed to be both causal and content-based. (Beliefs and desires cause the behaviours they do because they have the contents they do. For example, the desire that one have a beer and the beliefs that there is beer in the refrigerator and that the refrigerator is in the kitchen may explain one's getting up and going to the kitchen.) If, however, a mental representation's having a particular content is due to factors extrinsic to it, it is unclear how its having that content could determine its causal powers, which, arguably, must be intrinsic. Some who accept the standard arguments for externalism have argued that internal factors determine a component of the content of a mental representation. They say that mental representations have both ‘narrow’ content (determined by intrinsic factors) and ‘wide’ or ‘broad’ content (determined by narrow content plus extrinsic factors). (This distinction may be applied to the sub-personal representations of cognitive science as well as to those of commonsense psychology.
 Narrow content has been variously construed. Putnam (1975), Fodor (1982)), and Block (1986), for example, seem to understand it as something like de dicto content (i.e., Frégean sense, or perhaps character, à la Kaplan 1989). On this construal, narrow content is context-independent and directly expressible. Fodor (1987) and Block (1986), however, have also characterized narrow content as radically inexpressible. On this construal, narrow content is a kind of proto-content, or content-determinant, and can be specified only indirectly, via specifications of context/wide-content pairings. On both construal, narrow contents are characterized as functions from context to (wide) content. The narrow content of a representation is determined by properties intrinsic to it or its possessor such as its syntactic structure or its intra-mental computational or inferential role (or its phenomenology.
 Burge (1986) has argued that causation-based worries about externalist individuation of psychological content, and the introduction of the narrow notion, are misguided. Fodor (1994, 1998) has more recently urged that a scientific psychology might not need narrow content in order to supply naturalistic (causal) explanations of human cognition and action, since the sorts of cases they were introduced to handle, viz., Twin-Earth cases and Frége cases, are either nomologically impossible or dismissible as exceptions to non-strict psychological laws.
 The leading contemporary version of the Representational Theory of Mind, the Computational Theory of Mind (CTM), claims that the brain is a kind of computer and that mental processes are computations. According to the computational theory of mind, cognitive states are constituted by computational relations to mental representations of various kinds, and cognitive processes are sequences of such states. The computational theory of mind and the representational theory of mind, may by attempting to explain all psychological states and processes in terms of mental representation. In the course of constructing detailed empirical theories of human and animal cognition and developing models of cognitive processes implementable in artificial information processing systems, cognitive scientists have proposed a variety of types of mental representations. While some of these may be suited to be mental relata of commonsense psychological states, some-so-called ‘subpersonal’ or ‘sub-doxastic’ representations-are not. Though many philosophers believe that computational theory of mind can provide the best scientific explanations of cognition and behaviour, there is disagreement over whether such explanations will vindicate the commonsense psychological explanations of prescientific representational theory of mind.
 According to Stich's (1983) Syntactic Theory of Mind, for example, computational theories of psychological states should concern themselves only with the formal properties of the objects those states are relations to. Commitment to the explanatory relevance of content, however, is for most cognitive scientists fundamental (Fodor 1981, Pylyshyn 1984, Von Eckardt 1993). That mental processes are computations, which computations are rule-governed sequences of semantically evaluable objects, and that the rules apply to the symbols in virtue of their content, are central tenets of mainstream cognitive science.
 Explanations in cognitive science appeal to a many different kinds of mental representation, including, for example, the ‘mental models’ of Johnson-Laird 1983, the ‘retinal arrays,’ ‘primal sketches’ and ‘2½ -D sketches’ of Marr 1982, the ‘frames’ of Minsky 1974, the ‘sub-symbolic’ structures of Smolensky 1989, the ‘quasi-pictures’ of Kosslyn 1980, and the ‘interpreted symbol-filled arrays’ of Tye 1991-in addition to representations that may be appropriate to the explanation of commonsense psychological states. Computational explanations have been offered of, among other mental phenomena, belief (Fodor 1975, Field 1978), visual perception (Marr 1982, Osherson, et al. 1990), rationality (Newell and Simon 1972, Fodor 1975, Johnson-Laird and Wason 1977), language learning and  (Chomsky 1965, Pinker 1989), and musical comprehension (Lerdahl and Jackendoff 1983).
 A fundamental disagreement among proponents of computational theory of mind concerns the realization of personal-level representations (e.g., thoughts) and processes (e.g., inferences) in the brain. The central debate here is between proponents of Classical Architectures and proponents of Conceptionist Architectures.
 The classicists (e.g., Turing 1950, Fodor 1975, Fodor and Pylyshyn 1988, Marr 1982, Newell and Simon 1976) hold that mental representations are symbolic structures, which typically have semantically evaluable constituents, and that mental processes are rule-governed manipulations of them that are sensitive to their constituent structure. The connectionists (e.g., McCulloch & Pitts 1943, Rumelhart 1989, Rumelhart and McClelland 1986, Smolensky 1988) hold that mental representations are realized by patterns of activation in a network of simple processors (‘nodes’) and that mental processes consist of the spreading activation of such patterns. The nodes themselves are, typically, not taken to be semantically evaluable; nor do the patterns have semantically evaluable constituents. (Though there are versions of Connectionism-‘localist’ versions-on which individual nodes are taken to have semantic properties (e.g., Ballard 1986, Ballard & Hayes 1984).) It is arguable, however, that localist theories are neither definitive nor representative of the Conceptionist program (Smolensky 1988, 1991, Chalmers 1993).
 Classicists are motivated (in part) by properties thought seems to share with language. Fodor's Language of Thought Hypothesis (LOTH) (Fodor 1975, 1987), according to which the system of mental symbols constituting the neural basis of thought is structured like a language, provides a well-worked-out version of the classical approach as applied to commonsense psychology. According to the language of thought hypothesis, the potential infinity of complex representational mental states is generated from a finite stock of primitive representational states, in accordance with recursive formation rules. This combinatorial structure accounts for the properties of productivity and systematicity of the system of mental representations. As in the case of symbolic languages, including natural languages (though Fodor does not suppose either that the language of thought hypothesis explains only linguistic capacities or that only verbal creatures have this sort of cognitive architecture), these properties of thought are explained by appeal to the content of the representational units and their combinability into contentful complexes. That is, the semantics of both language and thought is compositional: the content of a complex representation is determined by the contents of its constituents and their structural configuration.
 Connectionists are motivated mainly by a consideration of the architecture of the brain, which apparently consists of layered networks of interconnected neurons. They argue that this sort of architecture is unsuited to carrying out classical serial computations. For one thing, processing in the brain is typically massively parallel. In addition, the elements whose manipulation drives computation in Conceptionist networks (principally, the connections between nodes) are neither semantically compositional nor semantically evaluable, as they are on the classical approach. This contrast with classical computationalism is often characterized by saying that representation is, with respect to computation, distributed as opposed to local: representation is local if it is computationally basic; and distributed if it is not. (Another way of putting this is to say that for classicists mental representations are computationally atomic, whereas for connectionists they are not.)
 Moreover, connectionists argue that information processing as it occurs in Conceptionist networks more closely resembles some features of actual human cognitive functioning. For example, whereas on the classical view learning involves something like hypothesis formation and testing (Fodor 1981), on the Conceptionist model it is a matter of evolving distribution of ‘weight’ (strength) on the connections between nodes, and typically does not involve the formulation of hypotheses regarding the identity conditions for the objects of knowledge. The Conceptionist network is ‘trained up’ by repeated exposure to the objects it is to learn to distinguish; and, though networks typically require many more exposures to the objects than do humans, this seems to model at least one feature of this type of human learning quite well.
 Further, degradation in the performance of such networks in response to damage is gradual, not sudden as in the case of a classical information processor, and hence more accurately models the loss of human cognitive function as it typically occurs in response to brain damage. It is also sometimes claimed that Conceptionist systems show the kind of flexibility in response to novel situations typical of human cognition-situations in which classical systems are relatively ‘brittle’ or ‘fragile.’
 Some philosophers have maintained that Connectionism entails that there are no propositional attitudes. Ramsey, Stich and Garon (1990) have argued that if Conceptionist models of cognition are basically correct, then there are no discrete representational states as conceived in ordinary commonsense psychology and classical cognitive science. Others, however (e.g., Smolensky 1989), hold that certain types of higher-level patterns of activity in a neural network may be roughly identified with the representational states of commonsense psychology. Still others (e.g., Fodor & Pylyshyn 1988, Heil 1991, Horgan and Tienson 1996) argue that language-of-thought style representation is both necessary in general and realizable within Conceptionist architectures. (MacDonald & MacDonald 1995 collects the central contemporary papers in the classicist/Conceptionist debate, and provides useful introductory material as well.
 Whereas Stich (1983) accepts that mental processes are computational, but denies that computations are sequences of mental representations, others accept the notion of mental representation, but deny that computational theory of mind provides the correct account of mental states and processes.
 Van Gelder (1995) denies that psychological processes are computational. He argues that cognitive systems are dynamic, and that cognitive states are not relations to mental symbols, but quantifiable states of a complex system consisting of (in the case of human beings) a nervous system, a body and the environment in which they are embedded. Cognitive processes are not rule-governed sequences of discrete symbolic states, but continuous, evolving total states of dynamic systems determined by continuous, simultaneous and mutually determining states of the systems' components. Representation in a dynamic system is essentially information-theoretic, though the bearers of information are not symbols, but state variables or parameters.
 Horst (1996), on the other hand, argues that though computational models may be useful in scientific psychology, they are of no help in achieving a philosophical understanding of the intentionality of commonsense mental states. computational theory of mind attempts to reduce the intentionality of such states to the intentionality of the mental symbols they are relations to. But, Horst claims, the relevant notion of symbolic content is essentially bound up with the notions of convention and intention. So the computational theory of mind involves itself in a vicious circularity: the very properties that are supposed to be reduced are (tacitly) appealed to in the reduction.
 To say that a mental object has semantic properties is, paradigmatically, to say that it may be about, or be true or false of, an object or objects, or that it may be true or false simpliciter. Suppose I think that ocelots take snuff. I am thinking about ocelots, and if what I think of them (that they take snuff) is true of them, then my thought is true. According to representational theory of mind such states are to be explained as relations between agents and mental representations. To think that ocelots take snuff is to token in some way a mental representation whose content is that ocelots take snuff. On this view, the semantic properties of mental states are the semantic properties of the representations they are relations to.
 Linguistic acts seem to share such properties with mental states. Suppose I say that ocelots take snuff. I am talking about ocelots, and if what I say of them (that they take snuff) is true of them, then my utterance is true. Now, to say that ocelots take snuff is (in part) to utter a sentence that means that ocelots take snuff. Many philosophers have thought that the semantic properties of linguistic expressions are inherited from the intentional mental states they are conventionally used to express (Grice 1957, Fodor 1978, Schiffer1972/1988, Searle 1983). On this view, the semantic properties of linguistic expressions are the semantic properties of the representations that are the mental relata of the states they are conventionally used to express.
 It is also widely held that in addition to having such properties as reference, truth-conditions and truth-so-called extensional properties-expressions of natural languages also have intensional properties, in virtue of expressing properties or propositions-i.e., in virtue of having meanings or senses, where two expressions may have the same reference, truth-conditions or truth value, yet express different properties or propositions (Frége 1892/1997). If the semantic properties of natural-language expressions are inherited from the thoughts and concepts they express (or vice versa, or both), then an analogous distinction may be appropriate for mental representations.
Søren Aabye Kierkegaard (1813-1855), a Danish religious philosopher, whose concern with individual existence, choice, and commitment profoundly influenced modern theology and philosophy, especially existentialism.
 Søren Kierkegaard wrote of the paradoxes of Christianity and the faith required to reconcile them. In his book Fear and Trembling, Kierkegaard discusses Genesis 22, in which God commands Abraham to kill his only son, Isaac. Although God made an unreasonable and immoral demand, Abraham obeyed without trying to understand or justify it. Kierkegaard regards this ‘leap of faith’ as the essence of Christianity.
 Kierkegaard was born in Copenhagen on May 15, 1813. His father was a wealthy merchant and strict Lutheran, whose gloomy, guilt-ridden piety and vivid imagination strongly influenced Kierkegaard. Kierkegaard studied theology and philosophy at the University of Copenhagen, where he encountered Hegelian philosophy and reacted strongly against it. While at the university, he ceased to practice Lutheranism and for a time led an extravagant social life, becoming a familiar figure in the theatrical and café society of Copenhagen. After his father's death in 1838, however, he decided to resume his theological studies. In 1840 he became engaged to the 17-year-old Regine Olson, but almost immediately he began to suspect that marriage was incompatible with his own brooding, complicated nature and his growing sense of a philosophical vocation. He abruptly broke off the engagement in 1841, but the episode took on great significance for him, and he repeatedly alluded to it in his books. At the same time, he realized that he did not want to become a Lutheran pastor. An inheritance from his father allowed him to devote himself entirely to writing, and in the remaining 14 years of his life he produced more than 20 books.
 Kierkegaard's work is deliberately unsystematic and consists of essays, aphorisms, parables, fictional letters and diaries, and other literary forms. Many of his works were originally published under pseudonyms. He applied the term existential to his philosophy because he regarded philosophy as the expression of an intensely examined individual life, not as the construction of a monolithic system in the manner of the 19th-century German philosopher Georg Wilhelm Friedrich Hegel, whose work he attacked in Concluding Unscientific Postscript (1846; trans. 1941). Hegel claimed to have achieved a complete rational understanding of human life and history; Kierkegaard, on the other hand, stressed the ambiguity and paradoxical nature of the human situation. The fundamental problems of life, he contended, defy rational, objective explanation; the highest truth is subjective.
 Kierkegaard maintained that systematic philosophy not only imposes a false perspective on human existence but that it also, by explaining life in terms of logical necessity, becomes a means of avoiding choice and responsibility. Individuals, he believed, create their own natures through their choices, which must be made in the absence of universal, objective standards. The validity of a choice can only be determined subjectively.
 In his first major work, Either/Or (2 volumes, 1843; trans. 1944), Kierkegaard described two spheres, or stages of existence, that the individual may choose: the aesthetic and the ethical. The aesthetic way of life is a refined hedonism, consisting of a search for pleasure and a cultivation of mood. The aesthetic individual constantly seeks variety and novelty in an effort to stave off boredom but eventually must confront boredom and despair. The ethical way of life involves an intense, passionate commitment to duty, to unconditional social and religious obligations. In his later works, such as Stages on Life's Way (1845; trans. 1940), Kierkegaard discerned in this submission to duty a loss of individual responsibility, and he proposed a third stage, the religious, in which one submits to the will of God but in doing so finds authentic freedom. In Fear and Trembling (1846; trans. 1941) Kierkegaard focused on God's command that Abraham sacrifice his son Isaac (Genesis 22: 1-19), an act that violates Abraham's ethical convictions. Abraham proves his faith by resolutely setting out to obey God's command, even though he cannot understand it. This ‘suspension of the ethical,’ as Kierkegaard called it, allows Abraham to achieve an authentic commitment to God. To avoid ultimate despair, the individual must make a similar ‘leap of faith’ into a religious life, which is inherently paradoxical, mysterious, and full of risk. One is called to it by the feeling of dread (The Concept of Dread,1844; trans. 1944), which is ultimately a fear of nothingness.
 Toward the end of his life Kierkegaard was involved in bitter controversies, especially with the established Danish Lutheran church, which he regarded as worldly and corrupt. His later works, such as The Sickness Unto Death (1849; trans. 1941), reflect an increasingly somber view of Christianity, emphasizing suffering as the essence of authentic faith. He also intensified his attack on modern European society, which he denounced in The Present Age (1846; trans. 1940) for its lack of passion and for its quantitative values. The stress of his prolific writing and of the controversies in which he engaged gradually undermined his health; in October 1855 he fainted in the street, and he died in Copenhagen on November 11, 1855.
 Kierkegaard's influence was at first confined to Scandinavia and to German-speaking Europe, where his work had a strong impact on Protestant theology and on such writers as the 20th-century Austrian novelist Franz Kafka. As existentialism emerged as a general European movement after World War I, Kierkegaard's work was widely translated, and he was recognized as one of the seminal figures of modern culture.
 Since scientists, during the nineteenth century were engrossed with uncovering the workings of external reality and seemingly knew of themselves that these virtually overflowing burdens of nothing, in that were about the physical substrates of human consciousness, the business of examining the distributive contribution in dynamic functionality and structural foundation of mind became the province of social scientists and humanists. Adolphe Quételet proposed a ‘social physics’ that could serve as the basis for a new discipline called sociology, and his contemporary Auguste Comte concluded that a true scientific understanding of the social reality was quite inevitable. Mind, in the view of these figures, was a separate and distinct mechanism subject to the lawful workings of a mechanical social reality.
 More formal European philosophers, such as Immanuel Kant, sought to reconcile representations of external reality in mind with the motions of matter-based on the dictates of pure reason. This impulse was also apparent in the utilitarian ethics of Jerry Bentham and John Stuart Mill, in the historical materialism of Karl Marx and Friedrich Engels, and in the pragmatism of Charles Smith, William James and John Dewey. These thinkers were painfully aware, however, of the inability of reason to posit a self-consistent basis for bridging the gap between mind and matter, and each remains obliged to conclude that the realm of the mental exists only in the subjective reality of the individual.
 The fatal flaw of pure reason is, of course, the absence of emotion, and purely explanations of the division between subjective reality and external reality, of which had limited appeal outside the community of intellectuals. The figure most responsible for infusing our understanding of the Cartesian dualism with contextual representation of our understanding with emotional content was the death of God theologian Friedrich Nietzsche 1844-1900. After declaring that God and ‘divine will’, did not exist, Nietzsche reified the ‘existence’ of consciousness in the domain of subjectivity as the ground for individual ‘will’ and summarily reducing all previous philosophical attempts to articulate the ‘will to truth’. The dilemma, forth in, had seemed to mean, by the validation, . . . as accredited for doing of science, in that the claim that Nietzsche’s earlier versions to the ‘will to truth’, disguises the fact that all alleged truths were arbitrarily created in the subjective reality of the individual and are expressed or manifesting the individualism of ‘will’.
 In Nietzsche’s view, the separation between mind and matter is more absolute and total than previously been imagined. Based on the assumption that there is no really necessary correspondence between linguistic constructions of reality in human subjectivity and external reality, he deuced that we are all locked in ‘a prison house of language’. The prison as he concluded it, was also a ‘space’ where the philosopher can examine the ‘innermost desires of his nature’ and articulate a new message of individual existence founded on ‘will’.
 Those who fail to enact their existence in this space, Nietzsche says, are enticed into sacrificing their individuality on the nonexistent altars of religious beliefs and democratic or socialists’ ideals and become, therefore, members of the anonymous and docile crowd. Nietzsche also invalidated the knowledge claims of science in the examination of human subjectivity. Science, he said. Is not exclusive to natural phenomenons and favors reductionistic examination of phenomena at the expense of mind? It also seeks to reduce the separateness and uniqueness of mind with mechanistic descriptions that disallow and basis for the free exercise of individual will.
 Nietzsche’s emotionally charged defense of intellectual freedom and radial empowerment of mind as the maker and transformer of the collective fictions that shape human reality in a soulless mechanistic universe proved terribly influential on twentieth-century thought. Furthermore, Nietzsche sought to reinforce his view of the subjective character of scientific knowledge by appealing to an epistemological crisis over the foundations of logic and arithmetic that arose during the last three decades of the nineteenth century. Through a curious course of events, attempted by Edmund Husserl 1859-1938, a German mathematician and a principal founder of phenomenology, wherefor to resolve this crisis resulted in a view of the character of consciousness that closely resembled that of Nietzsche.
 The best-known disciple of Husserl was Martin Heidegger, and the work of both figures greatly influenced that of the French atheistic existentialist Jean-Paul Sartre. The work of Husserl, Heidegger, and Sartre became foundational to that of the principal architects of philosophical postmodernism, and deconstructionist Jacques Lacan, Roland Barthes, Michel Foucault and Jacques Derrida. It obvious attribution of a direct linkage between the nineteenth-century crisis about the epistemological foundations of mathematical physics and the origin of philosophical postmodernism served to perpetuate the Cartesian two-world dilemma in an even more oppressive form. It also allows us better to understand the origins of cultural ambience and the ways in which they could resolve that conflict.
 The mechanistic paradigms of the late in the nineteenth century where the one Einstein came to know when he studied physics. Most physicists believed that it represented an eternal truth, but Einstein was open to fresh ideas. Inspired by Mach’s critical mind, he demolished the Newtonian ideas of space and time and replaced them with new, ‘relativistic’ notions.
 Jean-Paul Sartre (1905-1980), was a French philosopher, dramatist, novelist, and political journalist, who was a leading exponent of existentialism. Jean-Paul Sartre helped to develop existential philosophy through his writings, novels, and plays. Much of Sartre’s work focuses on the dilemma of choice faced by free individuals and on the challenge of creating meaning by acting responsibly in an indifferent world. In stating that ‘man is condemned to be free,’ Sartre reminds us of the responsibility that accompanies human decisions.
 Sartre was born in Paris, June 21, 1905, and educated at the Écôle Normale Supérieure in Paris, the University of Fribourg in Switzerland, and the French Institute in Berlin. He taught philosophy at various lycées from 1929 until the outbreak of World War II, when he was called into military service. In 1940-41 he was imprisoned by the Germans; after his release, he taught in Neuilly, France, and later in Paris, and was active in the French Resistance. The German authorities, unaware of his underground activities, permitted the production of his antiauthoritarian play The Flies (1943; trans. 1946) and the publication of his major philosophic work Being and Nothingness (1943; trans. 1953). Sartre gave up teaching in 1945 and founded the political and literary magazine Les Temps Modernes, of which he became editor in chief. Sartre was active after 1947 as an independent Socialist, critical of both the USSR and the United States in the so-called cold war years. Later, he supported Soviet positions but still frequently criticized Soviet policies. Most of his writing of the 1950s deals with literary and political problems. Sartre rejected the 1964 Nobel Prize in literature, explaining that to accept such an award would compromise his integrity as a writer.
Sartre's philosophic works combine the phenomenology of the German philosopher Edmund Husserl, the metaphysics of the German philosophers Georg Wilhelm Friedrich Hegel and Martin Heidegger, and the social theory of Karl Marx into a single view called existentialism. This view, which relates philosophical theory to life, literature, psychology, and political action, stimulated so much popular interest that existentialism became a worldwide movement.
 In his early philosophic work, Being and Nothingness, Sartre conceived humans as beings who create their own world by rebelling against authority and by accepting personal responsibility for their actions, unaided by society, traditional morality, or religious faith. Distinguishing between human existence and the nonhuman world, he maintained that human existence is characterized by nothingness, that is, by the capacity to negate and rebel. His theory of existential psychoanalysis asserted the inescapable responsibility of all individuals for their own decisions and made the recognition of one's absolute freedom of choice the necessary condition for authentic human existence. His plays and novels express the belief that freedom and acceptance of personal responsibility are the main values in life and that individuals must rely on their creative powers rather than on social or religious authority.
 In his later philosophic work Critique of Dialectical Reason (1960; trans. 1976), Sartre's emphasis shifted from existentialist freedom and subjectivity to Marxist social determinism. Sartre argued that the influence of modern society over the individual is so great as to produce serialization, by which he meant loss of self. Individual power and freedom can only be regained through group revolutionary action. Despite this exhortation to revolutionary political activity, Sartre himself did not join the Communist Party, thus retaining the freedom to criticize the Soviet invasions of Hungary in 1956 and Czechoslovakia in 1968. He died in Paris, April 15, 1980.
 The part of the theory of design or semiotics, that concerns the relationship between speakers and their signs. the study of the principles governing appropriate conversational moves is called general pragmatized, applied pragmatics treats of special  kinds of linguistic interaction such as inter-views and speech asking, nevertheless, the philosophical movement that has had a major impact on American culture from the late 19th century to the present. Pragmatism calls for ideas and theories to be tested in practice, by assessing whether acting upon the idea or theory produces desirable or undesirable results. According to pragmatists, all claims about truth, knowledge, morality, and politics must be tested in this way. Pragmatism has been critical of traditional Western philosophy, especially the notion that there are absolute truths and absolute values. Although pragmatism was popular for a time in France, England, and Italy, most observers believe that it encapsulates an American faith in know-how and practicality and an equally American distrust of abstract theories and ideologies.
 Pragmatists regard all theories and institutions as tentative hypotheses and solutions. For this reason they believed that efforts to improve society, through such means as education or politics, must be geared toward problem solving and must be ongoing. Through their emphasis on connecting theory to practice, pragmatist thinkers attempted to transform all areas of philosophy, from metaphysics to ethics and political philosophy.
 Pragmatism sought a middle ground between traditional ideas about the nature of reality and radical theories of nihilism and irrationalism, which had become popular in Europe in the late 19th century. Traditional metaphysics assumed that the world has a fixed, intelligible structure and that human beings can know absolute or objective truths about the world and about what constitutes moral behavior. Nihilism and irrationalism, on the other hand, denied those very assumptions and their certitude. Pragmatists today still try to steer a middle course between contemporary offshoots of these two extremes.
 The ideas of the pragmatists were considered revolutionary when they first appeared. To some critics, pragmatism’s refusal to affirm any absolutes carried negative implications for society. For example, pragmatists do not believe that a single absolute idea of goodness or justice exists, but rather that these concepts are changeable and depend on the context in which they are being discussed. The absence of these absolutes, critics feared, could result in a decline in moral standards. The pragmatists’ denial of absolutes, moreover, challenged the foundations of religion, government, and schools of thought. As a result, pragmatism influenced developments in psychology, sociology, education, semiotics (the study of signs and symbols), and scientific method, as well as philosophy, cultural criticism, and social reform movements. Various political groups have also drawn on the assumptions of pragmatism, from the progressive movements of the early 20th century to later experiments in social reform.
 Pragmatism is best understood in its historical and cultural context. It arose during the late 19th century, a period of rapid scientific advancement typified by the theories of British biologist Charles Darwin, whose theories suggested to many thinkers that humanity and society are in a perpetual state of progress. During this same period a decline in traditional religious beliefs and values accompanied the industrialization and material progress of the time. In consequence it became necessary to rethink fundamental ideas about values, religion, science, community, and individuality.
 The three most important pragmatists are American philosophers Charles Sanders Peirce, William James, and John Dewey. Peirce was primarily interested in scientific method and mathematics; his objective was to infuse scientific thinking into philosophy and society, and he believed that human comprehension of reality was becoming ever greater and that human communities were becoming increasingly progressive. Peirce developed pragmatism as a theory of meaning-in particular, the meaning of concepts used in science. The meaning of the concept ‘brittle,’ for example, is given by the observed consequences or properties that objects called ‘brittle’ exhibit. For Peirce, the only rational way to increase knowledge was to form mental habits that would test ideas through observation, experimentation, or what he called inquiry. Many philosophers known as logical positivists, a group of philosophers who have been influenced by Peirce, believed that our evolving species was fated to get ever closer to Truth. Logical positivists emphasize the importance of scientific verification, rejecting the assertion of positivism that personal experience is the basis of true knowledge.
 James moved pragmatism in directions that Peirce strongly disliked. He generalized Peirce’s doctrines to encompass all concepts, beliefs, and actions; he also applied pragmatist ideas to truth as well as to meaning. James was primarily interested in showing how systems of morality, religion, and faith could be defended in a scientific civilization. He argued that sentiment, as well as logic, is crucial to rationality and that the great issues of life-morality and religious belief, for example-are leaps of faith. As such, they depend upon what he called ‘the will to believe’ and not merely on scientific evidence, which can never tell us what to do or what is worthwhile. Critics charged James with relativism (the belief that values depend on specific situations) and with crass expediency for proposing that if an idea or action works the way one intends, it must be right. But James can more accurately be described as a pluralist-someone who believes the world to be far too complex for any one philosophy to explain everything.
 Dewey’s philosophy can be described as a version of philosophical naturalism, which regards human experience, intelligence, and communities as ever-evolving mechanisms. Using their experience and intelligence, Dewey believed, human beings can solve problems, including social problems, through inquiry. For Dewey, naturalism led to the idea of a democratic society that allows all members to acquire social intelligence and progress both as individuals and as communities. Dewey held that traditional ideas about knowledge, truth, and values, in which absolutes are assumed, are incompatible with a broadly Darwinian world-view in which individuals and society are progressing. In consequence, he felt that these traditional ideas must be discarded or revised. Indeed, for pragmatists, everything people know and do depends on a historical context and is thus tentative rather than absolute.
 Many followers and critics of Dewey believe he advocated elitism and social engineering in his philosophical stance. Others think of him as a kind of romantic humanist. Both tendencies are evident in Dewey’s writings, although he aspired to synthesize the two realms.
 The pragmatist tradition was revitalized in the 1980s by American philosopher Richard Rorty, who has faced similar charges of elitism for his belief in the relativism of values and his emphasis on the role of the individual in attaining knowledge. Interest has renewed in the classic pragmatists-Pierce, James, and Dewey-as an alternative to Rorty’s interpretation of the tradition.
 In an ever-changing world, pragmatism has many benefits. It defends social experimentation as a means of improving society, accepts pluralism, and rejects dead dogmas. But a philosophy that offers no final answers or absolutes and that appears vague as a result of trying to harmonize opposites may also be unsatisfactory to some.
 One of the five branches into which semiotics is usually divided the study of meaning of words, and their relation of designed to the object studied, a semantic is provided for a formal language when an interpretation or model is specified. Nonetheless, the Semantics, the Greek semantikos, ‘significant,’ the study of the meaning of linguistic signs- that is, words, expressions, and sentences. Scholars of semantics try to one answer such questions as ‘What is the meaning of (the word) X?’ They do this by studying what signs are, as well as how signs possess significance-that is, how they are intended by speakers, how they designate (make reference to things and ideas), and how they are interpreted by hearers. The goal of semantics is to match the meanings of signs-what they stand for-with the process of assigning those meanings.
 Semantics is studied from philosophical (pure) and linguistic (descriptive and theoretical) approaches, plus an approach known as general semantics. Philosophers look at the behavior that goes with the process of meaning. Linguists study the elements or features of meaning as they are related in a linguistic system. General semanticists concentrate on meaning as influencing what people think and do.
 These semantic approaches also have broader application. Anthropologists, through descriptive semantics, study what people categorize as culturally important. Psychologists draw on theoretical semantic studies that attempt to describe the mental process of understanding and to identify how people acquire meaning (as well as sound and structure) in language. Animal behaviorists research how and what other species communicate. Exponents of general semantics examine the different values (or connotations) of signs that supposedly mean the same thing (such as ‘the victor at Jena’ and ‘the loser at Waterloo,’ both referring to Napoleon). Also in a general-semantics vein, literary critics have been influenced by studies differentiating literary language from ordinary language and describing how literary metaphors evoke feelings and attitudes.
 In the late 19th century Michel Jules Alfred Breal, a French philologist, proposed a ‘science of significations’ that would investigate how sense is attached to expressions and other signs. In 1910 the British philosophers Alfred North Whitehead and Bertrand Russell published Principia Mathematica, which strongly influenced the Vienna Circle, a group of philosophers who developed the rigorous philosophical approach known as logical positivism.
 One of the leading figures of the Vienna Circle, the German philosopher Rudolf Carnap, made a major contribution to philosophical semantics by developing symbolic logic, a system for analyzing signs and what they designate. In logical positivism, meaning is a relationship between words and things, and its study is empirically based: Because language, ideally, is a direct reflection of reality, signs match things and facts. In symbolic logic, however, mathematical notation is used to state what signs designate and to do so more clearly and precisely than is possible in ordinary language. Symbolic logic is thus itself a language, specifically, a metalanguage (formal technical language) used to talk about an object language (the language that is the object of a given semantic study).
 An object language has a speaker (for example, a French woman) using expressions (such as la plume rouge) to designate a meaning (in this case, to indicate a definite pen-plume-of the color red-rouge). The full description of an object language in symbols is called the semiotic of that language. A language's semiotic has the following aspects: (1) a semantic aspect, in which signs (words, expressions, sentences) are given specific designations; (2) a pragmatic aspect, in which the contextual relations between speakers and signs are indicated; and (3) a syntactic aspect, in which formal relations among the elements within signs (for example, among the sounds in a sentence) are indicated.
 An interpreted language in symbolic logic is an object language together with rules of meaning that link signs and designations. Each interpreted sign has a truth condition-a condition that must be met in order for the sign to be true. A sign's meaning is what the sign designates when its truth condition is satisfied. For example, the expression or sign ‘the moon is a sphere’ is understood by someone who knows English; however, although it is understood, it may or may not be true. The expression is true if the thing it is extended to-the moon-is in fact spherical. To determine the sign's truth value, one must look at the moon for oneself.
 The symbolic logic of logical positivist philosophy thus represents an attempt to get at meaning by way of the empirical verifiability of signs-by whether the truth of the sign can be confirmed by observing something in the real world. This attempt at understanding meaning has been only moderately successful. The Austrian-British philosopher Ludwig Wittgenstein rejected it in favor of his ‘ordinary language’ philosophy, in which he asserted that thought is based on everyday language. Not all signs designate things in the world, he pointed out, nor can all signs be associated with truth values. In his approach to philosophical semantics, the rules of meaning are disclosed in how speech is used.
 From ordinary-language philosophy has evolved the current theory of speech-act semantics. The British philosopher J. L. Austin claimed that, by speaking, a person performs an act, or does something (such as state, predict, or warn), and that meaning is found in what an expression does, in the act it performs. The American philosopher John R. Searle extended Austin's ideas, emphasizing the need to relate the functions of signs or expressions to their social context. Searle asserted that speech encompasses at least three kinds of acts: (1) elocutionary acts, in which things are said with a certain sense or reference (as in ‘the moon is a sphere’); (2) illocutionary acts, in which such acts as promising or commanding are performed by means of speaking; and (3) perlocutionary acts, in which the speaker, by speaking, does something to someone else (for example, angers, consoles, or persuades someone). The speaker's intentions are conveyed by the illocutionary force that is given to the signs-that is, by the actions implicit in what is said. To be successfully meant, however, the signs must also be appropriate, sincere, consistent with the speaker's general beliefs and conduct, and recognizable as meaningful by the hearer.
 What has developed in philosophical semantics, then, is a distinction between truth-based semantics and speech-act semantics. Some critics of speech-act theory believe that it deals primarily with meaning in communication (as opposed to meaning in language) and thus is part of the pragmatic aspect of a language's semiotic-that it relates to signs and to the knowledge of the world shared by speakers and hearers, rather than relating to signs and their designations (semantic aspect) or to formal relations among signs (syntactic aspect). These scholars hold that semantics should be restricted to assigning interpretations to signs alone-independent of a speaker and hearer.
 Researchers in descriptive semantics examine what signs mean in particular languages. They aim, for instance, to identify what constitutes nouns or noun phrases and verbs or verb phrases. For some languages, such as English, this is done with subject-predicate analysis. For languages without clear-cut distinctions between nouns, verbs, and prepositions, it is possible to say what the signs mean by analyzing the structure of what are called propositions. In such an analysis, a sign is seen as an operator that combines with one or more arguments (also signs), often nominal arguments (noun phrases) or, relates nominal arguments to other elements in the expression (such as prepositional phrases or adverbial phrases). For example, in the expression ‘Bill gives Mary the book,’‘gives’ is an operator that relates the arguments ‘Bill,’‘Mary,’ and ‘the book.’
 Whether using subject-predicate analysis or propositional analysis, descriptive semanticists establish expression classes (classes of items that can substitute for one another within a sign) and classes of items within the conventional parts of speech (such as nouns and verbs). The resulting classes are thus defined in terms of syntax, and they also have semantic roles; that is, the items in these classes perform specific grammatical functions, and in so doing they establish meaning by predicating, referring, making distinctions among entities, relations, or actions. For example, ‘kiss’ belongs to an expression class with other items such as ‘hit’ and ‘see,’ as well as to the conventional part of speech ‘verb,’ in which it is part of a subclass of operators requiring two arguments (an actor and a receiver). In ‘Mary kissed John,’ the syntactic role of ‘kiss’ is to relate two nominal arguments (‘Mary’ and ‘John’), whereas its semantic role is to identify a type of action. Unfortunately for descriptive semantics, however, it is not always possible to find a one-to-one correlation of syntactic classes with semantic roles. For instance, ‘John’ has the same semantic role-to identify a person-in the following two sentences: ‘John is easy to please’ and ‘John is eager to please.’ The syntactic role of ‘John’ in the two sentences, however, is different: In the first, ‘John’ is the receiver of an action; in the second, ‘John’ is the actor.
 Linguistic semantics is also used by anthropologists called ethnoscientists to conduct formal semantic analysis (componential analysis) to determine how expressed signs-usually single words as vocabulary items called lexemes-in a language are related to the perceptions and thoughts of the people who speak the language. Componential analysis tests the idea that linguistic categories influence or determine how people view the world; this idea is called the Whorf hypothesis after the American anthropological linguist Benjamin Lee Whorf, who proposed it. In componential analysis, lexemes that have a common range of meaning constitute a semantic domain. Such a domain is characterized by the distinctive semantic features (components) that differentiate individual lexemes in the domain from one another, and also by features shared by all the lexemes in the domain. Such componential analysis points out, for example, that in the domain ‘seat’ in English, the lexemes ‘chair,’‘sofa,’‘loveseat,’ and ‘bench’ can be distinguished from one another according to how many people are accommodated and whether a back support is included. At the same time all these lexemes share the common component, or feature, of meaning ‘something on which to sit.’
 Linguists pursuing such componential analysis hope to identify a universal set of such semantic features, from which are drawn the different sets of features that characterize different languages. This idea of universal semantic features has been applied to the analysis of systems of myth and kinship in various cultures by the French anthropologist Claude Lévi-Strauss. He showed that people organize their societies and interpret their place in these societies in ways that, despite apparent differences, have remarkable underlying similarities.
 Linguists concerned with theoretical semantics are looking for a general theory of meaning in language. To such linguists, known as transformational-generative grammarians, meaning is part of the linguistic knowledge or competence that all humans possess. A generative grammar as a model of linguistic competence has a phonological (sound-system), a syntactic, and a semantic component. The semantic component, as part of a generative theory of meaning, is envisioned as a system of rules that govern how interpretable signs are interpreted and determine that other signs (such as ‘Colorless green ideas sleep furiously’), although grammatical expressions, are meaningless-semantically blocked. The rules must also account for how a sentence such as ‘They passed the port at midnight’ can have at least two interpretations.
 Generative semantics grew out of proposals to explain a speaker's ability to produce and understand new expressions where grammar or syntax fails. Its goal is to explain why and how, for example, a person understands at first hearing that the sentence ‘Colorless green ideas sleep furiously’ has no meaning, even though it follows the rules of English grammar; or how, in hearing a sentence with two possible interpretations (such as ‘They passed the port at midnight’), one decides which meaning applies.
 In generative semantics, the idea developed that all information needed to semantically interpret a sign (usually a sentence) is contained in the sentence's underlying grammatical or syntactic deep structure. The deep structure of a sentence involves lexemes (understood as words or vocabulary items composed of bundles of semantic features selected from the proposed universal set of semantic features). On the sentence's surface (that is, when it is spoken) these lexemes will appear as nouns, verbs, adjectives, and other parts of speech-that is, as vocabulary items. When the sentence is formulated by the speaker, semantic roles (such as subject, object, predicate) are assigned to the lexemes; the listener hears the spoken sentence and interprets the semantic features that are meant.
 Whether deep structure and semantic interpretation are distinct from one another is a matter of controversy. Most generative linguists agree, however, that a grammar should generate the set of semantically well-formed expressions that are possible in a given language, and that the grammar should associate a semantic interpretation with each expression.
 Another subject of debate is whether semantic interpretation should be understood as syntactically based (that is, coming from a sentence's deep structure); or whether it should be seen as semantically based. According to Noam Chomsky, an American scholar who is particularly influential in this field, it is possible-in a syntactically based theory-for surface structure and deep structure jointly to determine the semantic interpretation of an expression.
 The focus of general semantics is how people evaluate words and how that evaluation influences their behavior. Begun by the Polish American linguist Alfred Korzybski and long associated with the American semanticist and politician S. I. Hayakawa, general semantics has been used in efforts to make people aware of dangers inherent in treating words as more than symbols. It has been extremely popular with writers who use language to influence people's ideas. In their work, these writers use general-semantics guidelines for avoiding loose generalizations, rigid attitudes, inappropriate finality, and imprecision. Some philosophers and linguists, however, have criticized general semantics as lacking scientific rigor, and the approach has declined in popularity.
Positivism, system of philosophy based on experience and empirical knowledge of natural phenomena, in which metaphysics and theology are regarded as inadequate and imperfect systems of knowledge. The doctrine was first called positivism by the 19th-century French mathematician and philosopher Auguste Comte (1798-1857), but some of the positivist concepts may be traced to the British philosopher David Hume, the French philosopher Duc de Saint-Simon, and the German philosopher Immanuel Kant.
 Comte chose the word positivism on the ground that it indicated the ‘reality’ and ‘constructive tendency’ that he claimed for the theoretical aspect of the doctrine. He was, in the main, interested in a reorganization of social life for the good of humanity through scientific knowledge, and thus control of natural forces. The two primary components of positivism, the philosophy and the polity (or program of individual and social conduct), were later welded by Comte into a whole under the conception of a religion, in which humanity was the object of worship. A number of Comte's disciples refused, however, to accept this religious development of his philosophy, because it seemed to contradict the original positivist philosophy. Many of Comte's doctrines were later adapted and developed by the British social philosophers John Stuart Mill and Herbert Spencer and by the Austrian philosopher and physicist Ernst Mach.
 The principle named But rejected by the English economist and philosopher John Maynard Keyes (1883-1946) whereby if there is no known reason for asserting one than another out of several alternatives, then relative to our knowledge they have an equal probability. Without restriction the principle leads to contradiction, for example, if we know nothing about the nationality of a person, we might argfue that the probability is equal that she comes from England or France, and equal that she comes from Scotland or France. But from the first two assertions the probability that she belongs to Britain must be at least double the probability that be belongs to France.
 A paradox arises when a set class opf apparent incontrovertible premises gives unacceptable or contradictory conclusions. To solve a paradox will involve either showing that there is a hidden  flaw in the premises, or that the reasoning is erroneous, or that the apparently unacceptable conclusion can, in fact, be tolerated. Paradoxes are therefore important in philosophy, for until one is solved it shows that there is something about our reasoning and our concepts that we do not understand.
 By comparison, the moral philosopher and epistemologist Bernard Bolzano (1781-1848) argues, though, that there is something else, an infinity that doe not have this whatever you need it to be elasticity. In fact a truly infinite quantity (for example, the length of a straight ligne unbounded in either direction, meaning: The magnitude of the spatial entity containing all the points determined solely by their abstractly conceivable relation to two fixed points) does not by any means need to be variable, and in adduced example it is in fact not variable. Conversely, it is quite possible for a quantity merely capable of being taken greater than we have already taken it, and of becoming larger than any pre-assigned (finite) quantity, nevertheless it is to mean, in that of all times is merely finite, which holds in particular of every numerical quantity 1, 2, 3, 4, 5.
 In other words, for Bolzano there could be a true infinity that was not a variable something that was only bigger than anything you might specify. Such a true infinity was the result of joining two pints together and extending that ligne in both directions without stopping. And what is more, he could separate off the demands of calculus, using a finite quality without ever bothering with the slippery potential infinity. Here was both a deeper understanding of the nature of infinity and the basis on which are built in his safe infinity free calculus.
 This use of the inexhaustible follows on directly from most Bolzanos’ criticism of the way that ∞ we used as a variable something that would be bigger than anything you could specify, but never quite reached the true, absolute infinity. In Paradoxes of the Infinity Bolzano points out that is possible for a quantity merely capable of becoming larger than any one pre-assigned (finite) quantity, nevertheless to remain at all times merely finite.
 Bolzano intended this as a criticism of the way infinity was treated, but Professor Jacquette sees it instead of a way of masking use of practical applications like calculus without the need for weasel words about infinity.
 By replacing ∞ with ¤ we do away with one of the most common requirements for infinity, but is there anything left that map out to the real world? Can we confine infinity to that pure mathematical other world, where anything, however unreal, can be constructed, and forget about it elsewhere? Surprisingly, this seems to have been the view, at least at one point in time, even of the German mathematician and founder of set-theory Georg Cantor (1845-1918), himself, whose comments in 1883, that only the finite numbers are real.
 Keeping within the lines of reason, both the Cambridge mathematician and philosopher Frank Plumpton Ramsey (1903-30) and the Italian mathematician G. Peano (1858-1932) have been to distinguish logical paradoxes and that depend upon the notion of reference or truth (semantic notions), such are the postulates justifying mathematical induction. It ensures that a numerical series is closed, in the sense that nothing but zero and its successors can be numbers. In that any series satisfying a set of axioms can be conceived as the sequence of natural numbers. Candidates from set theory include the Zermelo numbers, where the empty set is zero, and the successor of each number is its unit set, and the von Neuman numbers, where each number is the set of all smaller numbers. A similar and equally fundamental complementarity exists in the relation between zero and infinity. Although the fullness of infinity is logically antithetical to the emptiness of zero, infinity can be obtained from zero with a simple mathematical operation. The division of many numbers by zero is infinity, while the multiplication of any number by zero is zero.
 With the set theory developed by the German mathematician and logician Georg Cantor. From 1878 to 1807, Cantor created a theory of abstract sets of entities that eventually became a mathematical discipline. A set, as he defined it, is a collection of definite and distinguished objects in thought or perception conceived as a whole.
 Cantor attempted to prove that the process of counting and the definition of integers could be placed on a solid mathematical foundation. His method was to repeatedly place the elements in one set into one-to-one correspondence with those in another. In the case of integers, Cantor showed that each integer (1, 2, 3, . . . n) could be paired with an even integers (2, 4, 6, . . . n), and, therefore, that the set of all integers was equal to the set of all even numbers.
 Amazingly, Cantor discovered that some infinite sets were large than others and that infinite sets formed a hierarchy of greater infinities. After this failed attempt to save the classical view of logical foundations and internal consistency of mathematical systems, it soon became obvious that a major crack had appeared in the seemingly sold foundations of number and mathematics. Meanwhile, an impressive number of mathematicians began to see that everything from functional analysis to the theory of real numbers depended on the problematic character of number itself.
 While, in the theory of probability Ramsey was the first to show how a personalized theory could be developed, based on precise behavioural notions of preference and expectation. In the philosophy of language, Ramsey was one of the first thinkers to accept a redundancy theory of truth, which hr combined with radical views of the function of man y kinds of propositions. Neither generalizations nor causal propositions, nor those treating probability or ethics, describe facts, but each has a different specific function in our intellectual economy.
 Ramsey advocates that of a sentence generated by taking all the sentence affirmed in a scientific theory that use some term, e.g., quark. Replacing the term by a variable, and existentially quantifying into the result. Instead of saying quarks have such-and-such properties, Ramsey postdated that the sentence as saying that there is something that has those properties. If the process is repeated, the sentence gives the topic-neutral structure of the theory, but removes any implications that we know what the term so treated denote. It leaves open the possibility of identifying the theoretical item with whatever it is that best fits the description provided. Nonetheless, it was pointed out by the Cambridge mathematician Newman that if the process is carried out for all except the logical bones of the theory, then by the Löwenheim-Skolem theorem, the result will be interpretable in any domain of sufficient cardinality, and the content of the theory may reasonably be felt to have been lost.
 It seems, that the most taken of paradoxes in the foundations of set theory as discovered by Russell in 1901. Some classes have themselves as members: The class of all abstract objects, for example, is an abstract object, whereby, others do not: The class of donkeys is not itself a donkey. Now consider the class of all classes that are not members of themselves, is this class a member of itself, that, if it is, then it is not, and if it is not, then it is.
 The paradox is structurally similar to easier examples, such as the paradox of the barber. Such one like a village having a barber in it, who shaves all and only the people who do not have in themselves. Who shaves the barber? If he shaves himself, then he does not, but if he does not shave himself, then he does not. The paradox is actually just a proof that there is no such barber or in other words, that the condition is inconsistent. All the same, it is no to easy to say why there is no such class as the one Russell defines. It seems that there must be some restriction on the kind of definition that are allowed to define classes and the difficulty that of finding a well-motivated principle behind any such restriction.
 The French mathematician and philosopher Henri Jules Poincaré (1854-1912) believed that paradoxes like those of Russell and the barber were due to such as the impredicative definitions, and therefore proposed banning them. But, it tuns out that classical mathematics required such definitions at too many points for the ban to be easily absolved. Having, in turn, as forwarded by Poincaré and Russell, was that in order to solve the logical and semantic paradoxes it would have to ban any collection (set) containing members that can only be defined by means of the collection taken as a whole. It is, effectively by all occurring principles into which have an adopting vicious regress, as to mark the definition for which involves no such failure. There is frequently room for dispute about whether regresses are benign or vicious, since the issue will hinge on whether it is necessary to reapply the procedure. The cosmological argument is an attempt to find a stopping point for what is otherwise seen as being an infinite regress, and, to ban of the predicative definitions.
 The investigation of questions that arise from reflection upon sciences and scientific inquiry, are such as called of a philosophy of science. Such questions include, what distinctions in the methods of science? s there a clear demarcation between scenes and other disciplines, and how do we place such enquires as history, economics or sociology? And scientific theories probable or more in the nature of provisional conjecture? Can the be verified or falsified? What distinguished good from bad explanations? Might there be one unified since, embracing all the special science? For much of the 20th century there questions were pursued in a highly abstract and logical framework it being supposed that as general logic of scientific discovery that a general logic of scientific discovery a justification might be found. However, many now take interests in a more historical, contextual and sometimes sociological approach, in which the methods and successes of a science at a particular time are regarded less in terms of universal logical principles and procedure, and more in terms of their availability to methods and paradigms as well as the social context.
 In addition, to general questions of methodology, there are specific problems within particular sciences, giving subjects as biology, mathematics and physics.
 The intuitive certainty that sparks aflame the dialectic awarenesses for its immediate concerns are either of the truth or by some other in an object of apprehensions, such as a concept. Awareness as such, has to its amounting quality value the place where philosophical understanding of the source of our knowledge are, however, in covering the sensible apprehension of things and pure intuition it is that which stricture sensation into the experience of things accent of its direction that orchestrates the celestial overture into measures in space and time.
 The notion that determines how something is seen or evaluated of the status of law and morality especially associated with St Thomas Aquinas and the subsequent scholastic tradition. More widely, any attempt to cement the moral and legal order together with the nature of the cosmos or how the nature of human beings, for which sense it is also found in some Protestant writers, and arguably derivative from a Platonic view of ethics, and is implicit in ancient Stoicism. Law stands above and apart from the activities of human lawmaker, it constitutes an objective set of principles that can be seen true by natural light or reason, and (in religion versions of the theory) that express Gods will for creation. Non-religious versions of the theory substitute objective conditions for human flourishing as the source of constraints upon permissible actions and social arrangements. Within the natural law tradition, different views have been held about the relationship between the rule of law about God s will, for instance the Dutch philosopher Hugo Grothius (1583-1645), similarly takes upon the view that the content of natural law is independent of any will, including that of God, while the German theorist and historian Samuel von Pufendorf (1632-94) takes the opposite view, thereby facing the problem of one horn of the Euthyphro dilemma, that simply states, that its dilemma arises from whatever the source of authority is supposed to be, for in which do we care about the general good because it is good, or do we just call good things that we care about. Wherefore, by facing the problem that may be to assume of a strong form, in which it is claimed that various facts entail values, or a weaker form, from which it confines itself to holding that reason by itself is capable of discerning moral requirements that are supped of binding to all human bings regardless of their desires
 Although the morality of people send the ethical amount from which the same thing, is that there is a usage that restricts morality to systems such as that of the German philosopher and founder of ethical philosophy Immanuel Kant (1724-1804), based on notions such as duty, obligation, and principles of conduct, reserving ethics for more than the Aristotelian approach to practical reasoning based on the notion of a virtue, and generally avoiding the separation of moral considerations from other practical considerations. The scholarly issues are complex, with some writers seeing Kant as more Aristotelian and Aristotle as, ore involved in a separate sphere of responsibility and duty, than the simple contrast suggests. Some theorists see the subject in terms of a number of laws (as in the Ten Commandments). The status of these laws may be test they are the edicts of a divine lawmaker, or that they are truths of reason, knowable deductively. Other approaches to ethics (e.g., eudaimonism, situation ethics, virtue ethics) eschew general principles as much as possible, frequently disguising the great complexity of practical reasoning. For Kantian notion of the moral law is a binding requirement of the categorical imperative, and to understand whether they are equivalent at some deep level. Kants own applications of the notion are not always convincing, as for one cause of confusion in relating Kants ethics to theories such additional expressivism is that it is easy, but mistaken, to suppose that the categorical nature of the imperative means that it cannot be the expression of sentiment, but must derive from something unconditional or necessary such as the voice of reason.
 For which ever reason, the mortal being makes of its presence to the future of weighing of that which one must do, or that which can be required of one. The term carries implications of that which is owed (due) to other people, or perhaps in onself. Universal duties would be owed to persons (or sentient beings) as such, whereas special duty in virtue of specific relations, such as being the child of someone, or having made someone a promise. Duty or obligation is the primary concept of deontological approaches to ethics, but is constructed in other systems out of other notions. In the system of Kant, a perfect duty is one that must be performed whatever the circumstances: Imperfect duties may have to give way to the more stringent ones. In another way, perfect duties are those that are correlative with the right to others, imperfect duties are not. Problems with the concept include the ways in which due needs to be specified (a frequent criticism of Kant is that his notion of duty is too abstract). The concept may also suggest of a regimented view of ethical life in which we are all forced conscripts in a kind of moral army, and may encourage an individualistic and antagonistic view of social relations.
 The most generally accepted account of externalism and/or internalism, that this distinction is that a theory of justification is internalist if only if it requiem that all of the factors needed for a belief to be epistemologically justified for a given person be cognitively accessible to that person, internal to cognitive perceptivity, and externalist, if it allows that at least some of the justifying factors need not be thus accessible, so that thy can be external to the believers cognitive perceptive, beyond any such given relations. However, epistemologists often use the distinction between internalist and externalist theories of epistemic justification without offering any very explicit explication.
 The externalist/internalist distinction has been mainly applied to theories of epistemic justification: It has also been applied in a closely related way to accounts of knowledge and in a rather different way to accounts of belief and thought contents.
 The internalist requirement of cognitive accessibility can be interpreted in at least two ways: A strong version of internalism would require that the believe actually be aware of the justifying factor in order to be justified: While a weaker version would require only that he be capable of becoming aware of them by focussing his attentions appropriately, but without the need for any change of position, new information, etc. Though the phrase cognitively accessible suggests the weak interpretation, the main intuitive motivation for internalism, viz the idea that epistemic justification requires that the believe actually have in his cognitive possession a reason for thinking that the belief is true, and would require the strong interpretation.
 Perhaps, the clearest example of an internalist position would be a Foundationalist view according to which foundational beliefs pertain to immediately experienced states of mind and other beliefs are justified by standing in cognitively accessible logical or inferential relations to such foundational beliefs. Such a view could count as either a strong or a weak version of internalism, depending on whether actual awareness of the justifying elements or only the capacity to become aware of them is required. Similarly, a coherent view could also be internalist, if both the beliefs or other states with which a justification belief is required to cohere and the coherence relations themselves are reflectively accessible.
 It should be carefully noticed that when internalism is construed in this way, it is neither necessary nor sufficient by itself for internalism that the justifying factors literally be internal mental states of the person in question. Not necessary, necessary, because on at least some views, e.g., a direct realist view of perception, something other than a mental state of the believe can be cognitively accessible: Not sufficient, because there are views according to which at least some mental states need not be actual (strong version) or even possible (weak version) objects of cognitive awareness. Also, on this way of drawing the distinction, a hybrid view, according to which some of the factors required for justification must be cognitively accessible while others need not and in general will not be, would count as an externalist view. Obviously too, a view that was externalist in relation to a strong version of internalism (by not requiring that the believe actually be aware of all justifiable factors) could still be internalist in relation to a weak version (by requiring that he at least be capable of becoming aware of them).
 The most prominent recent externalist views have been versions of reliabilism, whose requirements for justification is roughly that the belief be produced in a way or via a process that makes of objectively likely that the belief is true.  What makes such a view externalist is the absence of any requirement that the person for whom the belief is justified have any sort of cognitive access to the relations of reliability in question. Lacking such access, such a person will in general have no reason for thinking that the belief is true or likely to be true , but will, on such an account, nonetheless be epistemically justified in according it. Thus such a view arguably marks a major break from the modern epistemological tradition, stemming from Descartes, which identifies epistemic justification with having a reason, perhaps even a conclusive reason for thinking that the belief is true. An epistemologist working within this tradition is likely to feel that the externalist, than offering a competing account of the same concept of epistemic justification with which the traditional epistemologist is concerned, has simply changed the subject.
 The main objection to externalism rests on the intuitive certainty that the basic requirement for epistemic justification is that the acceptance of the belief in question be rational or responsible in relation to the cognitive goal of truth, which seems to require in turn that the believe actually be dialectally aware of a reason for thinking that the belief is true (or, at the very least, that such a reason be available to him). Since the satisfaction of an externalist condition is neither necessary nor sufficient for the existence of such a cognitively accessible reason, it is argued, externalism is mistaken as an account of epistemic justification. This general point has been elaborated by appeal to two sorts of putative intuitive counter-examples to externalism. The first of these challenges the necessity of belief which seem intuitively to be justified, but for which the externalist conditions are not satisfied. The standard examples in this sort are cases where beliefs are produced in some very nonstandard way, e.g., by a Cartesian demon, but nonetheless, in such a way that the subjective experience of the believe is indistinguishable from that of someone whose beliefs are produced more normally. The intuitive claim is that the believe in such a case is nonetheless epistemically justified, as much so as one whose belief is produced in a more normal way, and hence that externalist account of justification must be mistaken.
 Perhaps the most striking reply to this sort of counter-example, on behalf of a cognitive process is to be assessed in normal possible worlds, i.e., in possible worlds that are actually the way our world is common-seismically believed to be, than in the world which contains the belief being judged. Since the cognitive processes employed in the Cartesian demon cases are, for which we may assume, reliable when assessed in this way, the reliability can agree that such beliefs are justified. The obvious, to a considerable degree of bringing out the issue of whether it is or not an adequate rationale for this construal of Reliabilism, so that the reply is not merely a notional presupposition guised as having representation.
 The correlative way of elaborating on the general objection to justificatory externalism challenges the sufficiency of the various externalist conditions by citing cases where those conditions are satisfied, but where the believers in question seem intuitively not to be justified. In this context, the most widely discussed examples have to do with possible occult cognitive capacities, like clairvoyance. Considering the point in application once, again, to Reliabilism, the claim is that to think that he has such a cognitive power, and, perhaps, even good reasons to the contrary, is not rational or responsible and therefore not epistemically justified in accepting the belief that result from his clairvoyance, despite the fact that the Reliabilist condition is satisfied.
 One sort of response to this latter sorts of objection is to bite the bullet and insist that such believers are in fact justified, dismissing the seeming intuitions to the contrary as latent internalist prejudice. A more widely adopted response attempts to impose additional conditions, usually of a roughly internalized sort, which will rule out the offending example, while stopping far of a full internalism. But, while there is little doubt that such modified versions of externalism can handle particular cases, as well enough to avoid clear intuitive implausibility, the usually problematic cases that they cannot handle, and also whether there is and clear motivation for the additional requirements other than the general internalist view of justification that externalist are committed to reject.
 A view in this same general vein, one that might be described as a hybrid of internalism and externalism holds that epistemic justification requires that there is a justificatory factor that is cognitively accessible to the believe in question (though it need not be actually grasped), thus ruling out, e.g., a pure Reliabilism. At the same time, however, though it must be objectively true that beliefs for which such a factor is available are likely to be true, in addition, the fact need not be in any way grasped or cognitively accessible to the believe. In effect, of the premises needed to argue that a particular belief is likely to be true, one must be accessible in a way that would satisfy at least weakly internalized. The internalist will respond that this hybrid view is of no help at all in meeting the objection and has no belief nor is it held in the rational, responsible way that justification intuitively seems to require, for the believe in question, lacking one crucial premise, still has no reason at all for thinking that his belief is likely to be true.
 An alternative to giving an externalist account of epistemic justification, one which may be more defensible while still accommodating many of the same motivating concerns, is to give an externalist account of knowledge directly, without relying on an intermediate account of justification. Such a view will obviously have to reject the justified true belief account of knowledge, holding instead that knowledge is true belief which satisfies the chosen externalist condition, e.g., a result of a reliable process (and perhaps, further conditions as well). This makes it possible for such a view to retain internalist account of epistemic justification, though the centrality of that concept to epistemology would obviously be seriously diminished.
 Such an externalist account of knowledge can accommodate the commonsense conviction that animals, young children, and unsophisticated adults posses knowledge, though not the weaker conviction (if such a conviction does exists) that such individuals are epistemically justified in their beliefs. It is also at least less vulnerable to internalist counter-examples of the sort discussed, since the intuitions involved there pertain more clearly to justification than to knowledge. What is uncertain is what ultimate philosophical significance the resulting conception of knowledge is supposed to have. In particular, does it have any serious bearing on traditional epistemological problems and on the deepest and most troubling versions of scepticism, which seems in fact to be primarily concerned with justification, the an knowledge?`
 A rather different use of the terms internalism and externalism has to do with the issue of how the content of beliefs and thoughts is determined: According to an internalist view of content, the content of such intention states depends only on the non-relational, internal properties of the individuals mind or grain, and not at all on his physical and social environment: While according to an externalist view, content is significantly affected by such external factors and suggests a view that appears of both internal and external elements are standardly classified as an external view.
 As with justification and knowledge, the traditional view of content has been strongly internalized in character. The main argument for externalism derives from the philosophy of language, more specifically from the various phenomena pertaining to natural kind terms, indexicals, etc. that motivate the views that have come to be known as direct reference theories. Such phenomena seem at least to show that the belief or thought content that can be properly attributed to a person is dependant on facts about his environment, e.g., whether he is on Earth or Twin Earth, what is fact pointing at, the classificatory criteria employed by expects in his social group, etc.-not just on what is going on internally in his mind or brain.
 An objection to externalist account of content is that they seem unable to do justice to our ability to know the content of our beliefs or thought from the inside, simply by reflection. If content is depend on external factors pertaining to the environment, then knowledge of content should depend on knowledge of these factors-which will not in general be available to the person whose belief or thought is in question.
 The adoption of an externalized account of mental content would seem to support an externalist account of justification, by way that if part or all of the content of a belief inaccessible to the believe, then both the justifying status of other beliefs in relation to that content and the status of that content justifying the beliefs will be similarly inaccessible, thus contravening the internalist requirement for justification. An internalist must insist that there are no justifiable relations of these sorts, that our internally associable content can either be justified or justly anything else: But such a response appears lame unless it is coupled with an attempt to show that the externalist account of content is mistaken.
 A great deal of philosophical effort has been lavished on the attempt to naturalize content, i.e. to explain in non-semantic,. Non-intentional terms what it is for something to be represental (have content) and what it is for something to have some particular content rather than some other. There appear to be only four types of theory that have been proposed: Theories that ground representation in (1) similarity, (2) conversance, (3) functional role, (4) teleology.
 Similarly, theories hold that 'r' represents 'x' in virtue of being similar to 'x'. This has seemed hopeless to most as a theory of mental representation  because it appears to require that things in the brain must share properties with the things they represent: To represent a cat as furry appears to require something furry in the brain. Perhaps, a notion of similarity that is naturalistic and does not involve property sharing can be worked out, but it is not obvious how.
 Covariance theories hold that 'r's' represent 'x' is grounded in the fact that 'r's' occurrence canaries with that of 'x'. This is most compelling he n one thinks about detection systems, the firing a neural structures in the visual system is said to represent vertical orientations, if its firing varies with the occurrence of vertical lines in the visual field of perceptivity.
 Functional role theories hold that 'r's' represent 'x' is grounded in the functional role 'r' has in the representing system, i.e., on the relations imposed by specific cognitive processes imposed by specific cognitive processes between 'r' and other representations in the system's repertoire. Functional role theories take their cue from such common-sense ideas as that people cannot believer that cats are furry if they did not know that cats are animals or that fur is like hair.
 Teleological theories hold that 'r' represent 'x' if it is 'r's' function to indicate, i.e., covary with 'x'. Teleological theories differ depending on the theory of functions they import. Perhaps the most important distinction is that between historical theories of functions. Historical theories individuated functional states (hence contents) in a way that is sensitive to the historical development of the state, i.e., to factors such as the way the state was 'learned', or the way it evolved. An historical theory might hold that the function of 'r' is to indicate 'x' only if the capacity to token 'r' was developed (selected, learned) because it indicates 'x'. Thus, a state physically indistinguishable from 'r's' historical origins would not represent 'x' according to historical theories.
 Theories of representational content may be classified according to whether they are atomistic or holistic and according to whether they are externalistic or internalistic, whereby, emphasizing the priority of a whole over its parts. Furthermore, in the philosophy of language, this becomes the claim that the meaning of an individual word or sentence can only be understood in terms of its relation to an indefinitely larger body of language, such as a whole theory, or even a whole language or form of life. In the philosophy of mind a mental state similarly may be identified only in terms of its relations with others. Moderate holism may allow the other things besides these relationships also count; extreme holism would hold that a network of relationships is all that we have. A holistic view of science holds that experience only confirms or disconfirms large bodies of doctrine, impinging at the edges, and leaving some leeway over the adjustment that it requires.
 Once, again, in the philosophy of mind and language, the view that what is thought, or said, or experienced, is essentially dependent on aspects of the world external to the mind of the subject. The view goes beyond holding that such mental states are typically caused by external factors, to insist that they could not have existed as they now do without the subject being embedded in an external world of a certain kind. It is these external relations that make up the essence or identify of the mental state. Externalism is thus opposed to the Cartesian separation of the mental from the physical, since that holds that the mental could in principle exist as it does even if there were no external world at all. Various external factors have been advanced as ones on which mental content depends, including the usage of experts, the linguistic, norms of the community. And the general causal relationships of the subject. In the theory of knowledge, externalism is the view that a person might know something by being suitably situated with respect to it, without that relationship being in any sense within his purview. The person might, for example, be very reliable in some respect without believing that he is. The view allows that you can know without being justified in believing that you know.
 However, atomistic theories take a representation's content to be something that can be specified independent entity of that representation' s relations to other representations. What the American philosopher of mind, Jerry Alan Fodor (1935-) calls the crude causal theory, for example, takes a representation to be a |cow|-a menial representation with the same content as the word 'cow'-if its tokens are caused by instantiations of the property of being-a-cow, and this is a condition that places no explicit constraints on how |cow|'s must or might relate to other representations. Holistic theories contrasted with atomistic theories in taking the relations a representation bears to others to be essential to its content. According to functional role theories, a representation is a |cow| if it behaves like a |cow| should behave in inference.
 Internalist theories take the content of a representation to be a matter determined by factors internal to the system that uses it. Thus, what Block (1986) calls 'short-armed' functional role theories are internalist. Externalist theories take the content of a representation to be determined, in part at least, by factors external to the system that uses it. Covariance theories, as well as telelogical theories that invoke an historical theory of functions, take content to be determined by 'external' factors. Crossing the atomist-holistic distinction with the internalist-externalist distinction.
 Externalist theories (sometimes called non-individualistic theories) have the consequence that molecule for molecule are coincide with the identical cognitive systems might yet harbour representations with different contents. This has given rise to a controversy concerning 'narrow' content. If we assume some form of externalist theory is correct, then content is, in the first instance 'wide' content, i.e., determined in part by factors external to the representing system. On the other hand, it seems clear that, on plausible assumptions about how to individuate psychological capacities, internally equivalent systems must have the same psychological capacities. Hence, it would appear that wide content cannot be relevant to characterizing psychological equivalence. Since cognitive science generally assumes that content is relevant to characterizing psychological equivalence, philosophers attracted to externalist theories of content have sometimes attempted to introduce 'narrow' content, i.e., an aspect or kind of content that is equivalent internally equivalent systems. The simplest such theory is Fodor's idea (1987) that narrow content is a function from contents (i.e., from whatever the external factors are) to wide contents.
 All the same, what a person expresses by a sentence is often a function of the environment in which he or she is placed. For example, the disease I refer to by the term like 'arthritis', or the kind of tree I refer to as a 'Maple' will be defined by criteria of which I know next to nothing. This raises the possibility of imagining two persons in rather different environments, but in which everything appears the same to each of them. The wide content of their thoughts and sayings will be different if the situation surrounding them is appropriately different: 'situation' may include the actual objects they perceive or the chemical or physical kinds of object in the world they inhabit, or the history of their words, or the decisions of authorities on what counts as an example, of one of the terms they use. The narrow content is that part of their thought which remains identical, through their identity of the way things appear, regardless of these differences of surroundings. Partisans of wide content may doubt whether any content in this sense narrow, partisans of narrow content believer that it is the fundamental notion, with wide content being explicable in terms of narrow content plus context.
 Even so, the distinction between facts and values has outgrown its name: it applies not only to matters of fact vs, matters of value, but also to statements that something is, vs. statements that something ought to be. Roughly, factual statements-'is statements' in the relevant sense-represent some state of affairs as obtaining, whereas normative statements-evaluative, and deontic ones-attribute goodness to something, or ascribe, to an agent, an obligation to act. Neither distinction is merely linguistic. Specifying a book's monetary value is making a factual statement, though it attributes a kind of value. 'That is a good book' expresses a value judgement though the term 'value' is absent (nor would 'valuable' be synonymous with 'good'). Similarly, 'we are morally obligated to fight' superficially expresses a statement, and 'By all indications it ough to rain' makes a kind of ought-claim; but the former is an ought-statement, the latter an (epistemic) is-statement.
 Theoretical difficulties also beset the distinction. Some have absorbed values into facts holding that all value is instrumental, roughly, to have value is to contribute-in a factual analyzable way-to something further which is (say) deemed desirable. Others have suffused facts with values, arguing that facts (and observations) are 'theory-impregnated' and contending that values are inescapable to theoretical choice. But while some philosophers doubt that fact/value distinctions can be sustained, there persists a sense of a deep difference between evaluating, or attributing an obligation and, on the other hand, saying how the world is.
 Fact/value distinctions, may be defended by appeal to the notion of intrinsic value, value a thing has in itself and thus independently of its consequences. Roughly, a value statement (proper) is an ascription of intrinsic value, one to the effect that a thing is to some degree good in itself. This leaves open whether ought-statements are implicitly value statements, but even if they imply that something has intrinsic value-e.g., moral value-they can be independently characterized, say by appeal to rules that provide (justifying) reasons for action. One might also ground the fact value distinction in the attributional (or even motivational) component apparently implied by the making of valuational or deontic judgements: Thus, 'it is a good book, but that is no reason for a positive attribute towards it' and 'you ought to do it, but there is no reason to' seem inadmissible, whereas, substituting, 'an expensive book' and 'you will do it' yields permissible judgements. One might also argue that factual judgements are the kind which are in principle appraisable scientifically, and thereby anchor the distinction on the factual side. This ligne is plausible, but there is controversy over whether scientific procedures are 'value-free' in the required way.
 Philosophers differ regarding the sense, if any, in which epistemology is normative (roughly, valuational). But what precisely is at stake in this controversy is no clearly than the problematic fact/value distinction itself. Must epistemologists as such make judgements of value or epistemic responsibility? If epistemology is naturalizable, then even epistemic principles simply articulate under what conditions-say, appropriate perceptual stimulations-a belief is justified, or constitutes knowledge. Its standards of justification, then would be like standards of, e.g., resilience for bridges. It is not obvious, however, that there appropriate standards can be established without independent judgements that, say, a certain kind of evidence is good enough for justified belief (or knowledge). The most plausible view may be that justification is like intrinsic goodness, though it supervenes on natural properties, it cannot be analysed wholly in factual statements.
 Thus far, belief has been depicted as being all-or-nothing, however, as a resulting causality for which we have grounds for thinking it true, and, all the same, its acceptance is governed by epistemic norms, and, least of mention, it is partially subject to voluntary control and has functional affinities to belief. Still, the notion of acceptance, like that of degrees of belief, merely extends the standard picture, and does not replace it.
 Traditionally, belief has been of epistemological interest in its propositional guise: 'S' believes that 'p', where 'p' is a reposition towards which an agent, 'S' exhibits an attitude of acceptance. Not all belief is of this sort. If I trust you to say, I believer you. And someone may believer in Mr. Notgot, or in a free-market economy, or in God. It is sometimes supposed that all belief is 'reducible' to propositional belief, belief-that. Thus, my believing you might be thought a matter of my believing, is,  perhaps, that what you say is true, and your belief in free markets or God, is a matter of your believing that free-market economies are desirable or that God exists.
 Some philosophers have followed St, Thomas Aquinas (1225-74), in supposing that to believer in God is simply to believer that certain truths hold while others argue that belief-in is a distinctive attitude, on that includes essentially an element of trust. More commonly, belief-in has been taken to involve a combination of propositional belief together with some further attitude.
 The moral philosopher Richard Price (1723-91) defends the claim that there are different sorts of belief-in, some, but not all reducible to beliefs-that. If you believer in God, you believer that God exists, that God is good, you believer that God is good, etc. But according to Price, your belief involves, in addition, a certain complex pro-attitude toward its object. Even so, belief-in outruns the evidence for the corresponding belief-that. Does this diminish its rationality? If belief-in presupposes believes-that, it might be thought that the evidential standards for the former must be, at least, as high as standards for the latter. And any additional pro-attitude might be thought to require a further layer of justification not required for cases of belief-that.
 Belief-in may be, in general, less susceptible to alternations in the face of unfavourable evidence than belief-that. A believe who encounters evidence against God's existence may remain unshaken in his belief, in part because the evidence does not bear on his pro-attitude. So long as this is united with his belief that God exists, the reasonably so in a way that an ordinary propositional belief that would not.
 Some philosophers think that the category of knowing for which true. Justified believing (accepting) is a requirement constituting only a species of Propositional knowledge, construed as an even broader category. They have proposed various examples of 'PK' that do not satisfy the belief and/ort justification conditions of the tripartite analysis. Such cases are often recognized by analyses of Propositional knowledge in terms of powers, capacities, or abilities. For instance, Alan R. White (1982) treats 'PK' as merely the ability to provide a correct answer to a possible questions, however, White may be equating 'producing' knowledge in the sense of producing 'the correct answer to a possible question' with 'displaying' knowledge in the sense of manifesting knowledge. (White, 1982). The latter can be done even by very young children and some non-human animals independently of their being asked questions, understanding questions, or recognizing answers to questions. Indeed, an example that has been proposed as an instance of knowing that 'h' without believing or accepting that 'h' can be modified so as to illustrate this point. Two examples concerns an imaginary person who has no special training or information about horses or racing, but who in an experiment persistently and correctly picks the winners of upcoming horseraces. If the example is modified so that the hypothetical 'seer' never picks winners but only muses over whether those horses wight win, or only reports those horses winning, this behaviour should be as much of a candidate for the person's manifesting knowledge that the horse in question will win as would be the behaviour of picking it as a winner.
 These considerations expose limitations in Edward Craig's analysis (1990) of the concept of knowing of a person's being a satisfactory informant in relation to an inquirer who wants to find out whether or not 'h'. Craig realizes that counterexamples to his analysis appear to be constituted by Knower who are too recalcitrant to inform the inquirer, or too incapacitate to inform, or too discredited to be worth considering (as with the boy who cried 'Wolf'). Craig admits that this might make preferable some alternative view of knowledge as a different state that helps to explain the presence of the state of being a suitable informant when the latter does obtain. Such the alternate, which offers a recursive definition that concerns one's having the power to proceed in a way representing the state of affairs, causally involved in one's proceeding in this way. When combined with a suitable analysis of representing, this theory of propositional knowledge can be unified with a structurally similar analysis of knowing how to do something.
 Knowledge and belief, according to most epistemologists, knowledge entails belief, so that I cannot know that such and such is the case unless I believe that such and such is the case. Others think this entailment thesis can be rendered more accurately if we substitute for belief some closely related attitude. For instance, several philosophers would prefer to say that knowledge entail psychological certainties (Prichard, 1950 and Ayer, 1956) or conviction (Lehrer, 1974) or acceptance (Lehrer, 1989). None the less, there are arguments against all versions of the thesis that knowledge requires having a belief-like attitude toward the known. These arguments are given by philosophers who think that knowledge and belief (or a facsimile) are mutually incompatible (the incomparability thesis), or by ones who say that knowledge does not entail belief, or vice versa, so that each may exist without the other, but the two may also coexist (the separability thesis).
 The incompatibility thesis is sometimes traced to Plato ©. 429-347 BC) in view of his claim that knowledge is infallible while belief or opinion is fallible ('Republic' 476-9). But this claim would not support the thesis. Belief might be a component of an infallible form of knowledge in spite of the fallibility of belief. Perhaps, knowledge involves some factor that compensates for the fallibility of belief.
 A. Duncan-Jones (1939: Also Vendler, 1978) cite linguistic evidence to back up the incompatibility thesis. He notes that people often say 'I do not believe she is guilty. I know she is' and the like, which suggest that belief rule out knowledge. However, as Lehrer (1974) indicates, the above exclamation is only a more emphatic way of saying 'I do not just believe she is guilty, I know she is' where 'just' makes it especially clear that the speaker is signalling that she has something more salient than mere belief, not that she has something inconsistent with belief, namely knowledge. Compare: 'You do not hurt him, you killed him'.
 H.A. Prichard (1966) offers a defence of the incompatibility thesis that hinges on the equation of knowledge with certainty (both infallibility and psychological certitude) and the assumption that when we believe in the truth of a claim we are not certain about its truth. Given that belief always involves uncertainty while knowledge never dies, believing something rules out the possibility of knowing it. Unfortunately, however, Prichard gives 'us' no goods reason to grant that states of belief are never ones involving confidence. Conscious beliefs clearly involve some level of confidence, to suggest that we cease to believe things about which we are completely confident is bizarre.
 A.D. Woozley (1953) defends a version of the separability thesis. Woozley's version, which deals with psychological certainty rather than belief per se, is that knowledge can exist in the absence of confidence about the item known, although might also be accompanied by confidence as well. Woozley remarks that the test of whether I know something is 'what I can do, where what I can do may include answering questions'. On the basis of this remark he suggests that even when people are unsure of the truth of a claim, they might know that the claim is true. We unhesitatingly attribute knowledge to people who give correct responses on examinations even if those people show no confidence in their answers. Woozley acknowledges, however, that it would be odd for those who lack confidence to claim knowledge. It would be peculiar to say, 'I am unsure whether my answer is true: Still, I know it is correct'. But this tension Woozley explains using a distinction between conditions under which we are justified in making a claim (such as a claim to know something), and conditions under which the claim we make is true. While 'I know such and such' might be true even if I am unsure whether such and such holds, nonetheless it would be inappropriate for me to claim that I know that such and such unless I were sure of the truth of my claim.
 Colin Radford (1966) extends Woozley's defence of the separability thesis. In Radford's view, not only is knowledge compatible with the lack of certainty, it is also compatible with a complete lack of belief. He argues by example. In one example, Jean has forgotten that he learned some English history year's priori and yet he is able to give several correct responses to questions such as 'When did the Battle of Hastings occur'? Since he forgot that he took history, he considers the correct response to be no more than guesses. Thus, when he says that the Battle of Hastings took place in 1066 he would deny having the belief that the Battle of Hastings took place in 1066. A disposition he would deny being responsible (or having the right to be convincing) that 1066 was the correct date. Radford would none the less insist that Jean know when the Battle occurred, since clearly be remembering the correct date. Radford admits that it would be inappropriate for Jean to say that he knew when the Battle of Hastings occurred, but, like Woozley he attributes the impropriety to a fact about when it is and is not appropriate to claim knowledge. When we claim knowledge, we ought, at least to believe that we have the knowledge we claim, or else our behaviour is 'intentionally misleading'.
 Those that agree with Radford's defence of the separability thesis will probably think of belief as an inner state that can be detected through introspection. That Jean lack's beliefs about English history is plausible on this Cartesian picture since Jean does not find himself with any beliefs about English history when ne seek them out. One might criticize Radford, however, by rejecting that Cartesian view of belief. One could argue that some beliefs are thoroughly unconscious, for example. Or one could adopt a behaviourist conception of belief, such as Alexander Bain's (1859), according to which having beliefs is a matter of the way people are disposed to behave (and has not Radford already adopted a behaviourist conception of knowledge?) Since Jean gives the correct response when queried, a form of verbal behaviour, a behaviourist would be tempted to credit him with the belief that the Battle of Hastings occurred in 1066.
 D.M. Armstrong (1873) takes a different tack against Radford. Jean does know that the Battle of Hastings took place in 1066. Armstrong will grant Radfod that point, in fact, Armstrong suggests that Jean believe that 1066 is not the date the Battle of Hastings occurred, for Armstrong equates the belief that such and such is just possible but no more than just possible with the belief that such and such is not the case. However, Armstrong insists, Jean also believes that the Battle did occur in 1066. After all, had Jean been mistaught that the Battle occurred in 1066, and subsequently 'guessed' that it took place in 1066, we would surely describe the situation as one in which Jean's false belief about the Battle became unconscious over time but persisted of a memory trace that was causally responsible for his guess. Out of consistency, we must describe Radford's original case as one that Jean's true belief became unconscious but persisted long enough to cause his guess. Thus, while Jean consciously believes that the Battle did not occur in 1066, unconsciously he does believe it occurred in 1066. So after all, Radford does not have a counterexample to the claim that knowledge entails belief.
 Armstrong's response to Radford was to reject Radford's claim that the examinee lacked the relevant belief about English history. Another response is to argue that the examinee lacks the knowledge Radford attributes to him (cf. Sorenson, 1982). If Armstrong is correct in suggesting that Jean believes both that 1066 is and that it is not the date of the Battle of Hastings, one might deny Jean knowledge on the grounds that people who believe the denial of what they believe cannot be said t know the truth of their belief. Another strategy might be to compare the examine case with examples of ignorance given in recent attacks on externalist accounts of knowledge (needless to say.  Externalists themselves would tend not to favour this strategy). Consider the following case developed by BonJour (1985): For no apparent reason, Samantha believes that she is clairvoyant. Again, for no apparent reason, she one day comes to believe that the President is in New York City, even though she has every reason to believe that the President is in Washington, D.C. In fact, Samantha is a completely reliable clairvoyant, and she has arrived at her belief about the whereabouts of the President thorough the power of her clairvoyance. Yet surely Samantha's belief is completely irrational. She is not justified in thinking what she does. If so, then she does not know where the President is. But Radford's examinee is unconventional. Even if Jean lacks the belief that Radford denies him, Radford does not have an example of knowledge that is unattended with belief. Suppose that Jean's memory had been sufficiently powerful to produce the relevant belief. As Radford says, in having every reason to suppose that his response is mere guesswork, and he has every reason to consider his belief false. His belief would be an irrational one, and hence one about whose truth Jean would be ignorant.
 Least has been of mention to an approaching view from which 'perception' basis upon itself as a fundamental philosophical topic both for its central place in ant theory of knowledge, and its central place un any theory of consciousness. Philosophy in this area is constrained by a number of properties that we believe to hold of perception, (1) It gives 'us' knowledge of the world around 'us'. (2) We are conscious of that world by being aware of 'sensible qualities': Colour, sounds, tastes, smells, felt warmth, and the shapes and positions of objects in the environment. (3) Such consciousness is effected through highly complex information channels, such as the output of the three different types of colour-sensitive cells in the eye, or the channels in the ear for interpreting pulses of air pressure as frequencies of sound. (4) There ensues even more complex neurophysiological coding of that information, and eventually higher-order brain functions bring it about that we interpreted the information so received. (Much of this complexity has been revealed by the difficulties of writing programs enabling computers to recognize quite simple aspects of the visual scene.) The problem is to avoid thinking of here being a central, ghostly, conscious self, fed information in the same way that a screen if fed information by a remote television camera. Once such a model is in place, experience will seem like a veil getting between 'us' and the world, and the direct objects of perception will seem to be private items in an inner theatre or sensorium. The difficulty of avoiding this model is epically cute when we considered the secondary qualities of colour, sound, tactile feelings and taste, which can easily seem to have a purely private existence inside the perceiver, like sensation of pain. Calling such supposed items names like 'sense-data' or 'percepts' exacerbates the tendency, but once the model is in place, the first property, that perception gives 'us' knowledge of the world and its surrounding surfaces, is quickly threatened, for there will now seem little connection between these items in immediate experience and any independent reality. Reactions to this problem include 'scepticism' and 'idealism'.
 A more hopeful approach is to claim that the complexities of (3) and (4) explain how we can have direct acquaintance of the world, than suggesting that the acquaintance we do have been at best indirect. It is pointed out that perceptions are not like sensation, precisely because they have a content, or outer-directed nature. To have a perception is to be aware of the world for being such-and-such a way, than to enjoy a mere modification of sensation. But such direct realism has to be sustained in the face of the evident personal (neurophysiological and other) factors determining haw we perceive. One approach is to ask why it is useful to be conscious of what we perceive, when other aspects of our functioning work with information determining responses without any conscious awareness or intervention. A solution to this problem would offer the hope of making consciousness part of the natural world, than a strange optional extra.
 Furthering, perceptual knowledge is knowledge acquired by or through the senses and includes most of what we know. We cross intersections when we see the light turn green, head for the kitchen when we smell the roast burning, squeeze the fruit to determine its ripeness, and climb out of bed when we hear the alarm ring. In each case we come to know something-that the light has turned green, that the roast is burning, that the melon is overripe, and that it is time to get up-by some sensory means. Seeing that the light has turned green is learning something-that, the light has turned green-by use of the eyes. Feeling that the melon is overripe is coming to know a fact-that the melon is overripe-by one's sense to touch. In each case the resulting knowledge is somehow based on, derived from or grounded in the sort of experience that characterizes the sense modality in question.
 Much of our perceptual knowledge is indirect, dependent or derived. By this I mean that the facts we describe ourselves as learning, as coming to know, by perceptual means are pieces of knowledge that depend on our coming to know something else, some other fact, in a more direct way. We see, by the gauge, that we need gas, see, by the newspapers, that our team has lost again, see, by her expression, that she is nervous. This derived or dependent sort of knowledge is particularly prevalent in the cases of vision, but it occurs, to a lesser degree, in every sense modality. We install bells and other noise-makers so that we calm for example, hear (by the bell) that someone is at the door and (by the alarm) that its time to get up. When we obtain knowledge in this way, it is clear that unless one sees-hence, comes to know something about the gauge (that it says) and (hence, know) that one is described as coming to know by perceptual means. If one cannot hear that the bell is ringing, one cannot-in at least in this way-hear that one's visitors have arrived. In such cases one sees (hears, smells, etc.) that 'a' is 'F', coming to know thereby that 'a' is 'F', by seeing (hearing, etc.) that some other condition, 'b's' being 'G', obtains when this occurs, the knowledge (that 'a' is 'F') is derived from, or dependent on, the more basic perceptual knowledge that 'b' is 'G'.
 Perhaps as a better strategy is to tie an account save that part that evidence could justify explanation for it is its truth alone. Since, at least the time of Aristotle philosophers of explanatory knowledge have emphasizes of its importance that, in its simplest therms, we want to know not only what are the composite peculiarities and particulars points of issue but also why it is. This consideration suggests that we define an explanation as an answer to a why-question. Such a definition would, however, be too broad, because some why-questions are requests for consolation (Why did my son have to die?) Or moral justification (Why should women not be paid the same as men for the same work?) It would also be too narrow because some explanations are responses to how-questions (How does radar work?) Or how-possibility-questions (How is it possible for cats always to land their feet?)
 In its overall sense, 'to explain' means to make clear, to make plain, or to provide understanding. Definition of this sort are philosophically unhelpful, for the terms used in the deficient are no less problematic than the term to be defined. Moreover, since a wide variety of things require explanation, and since many different types of explanation exist, as more complex explanation is required. To facilitate the requirement leaves, least of mention, for us to consider by introduction a bit of technical terminology. The term 'explanation' is used to refer to that which is to be explained: The term 'explanans' refers to that which does the explaining, the explanans and the explanation taken together constitute the explanation.
 One common type of explanation occurs when deliberate human actions are explained in terms of conscious purposes. 'Why did you go to the pharmacy yesterday?' 'Because I had a headache and needed to get some aspirin.' It is tacitly assumed that aspirin is an appropriate medication for headaches and that going t the pharmacy would bean efficient way of getting some. Such explanations are, of course, teleological, referring, ss they do, to goals. The explanans is not the realisation of a future goal-if the pharmacy happened to be closed for stocktaking the aspirin would have ben obtained there, bu t that would not invalidate the explanation. Some philosophers would say that the antecedent desire to achieve the end is what doers the explaining: Others might say that the explaining is done by the nature of the goal and the fact that the action promoted the chances of realizing it. (Taylor, 1964). In that it should not be automatically be assumed that such explanations are causal. Philosophers differ considerably on whether these explanations are to be framed in terms of cause or reason, but the distinction cannot be used to show that the relation between reasons and the actions they justify is in no way causal, and there are many differing analyses of such concepts as intention and agency. Expanding the domain beyond consciousness, Freud maintained, in addition, that much human behaviour can be explained in terms of unconscious and conscious wishes. Those Freudian explanations should probably be construed as basically causal.
 Problems arise when teleological explanations are offered in other context. The behaviour of non-human animals is often explained in terms of purpose, e.g., the mouse ran to escape from the cat. In such cases the existence of conscious purpose seems dubious. The situation is still more problematic when a supr-empirical purpose in invoked, e.g., the explanations of living species in terms of God's purpose, or the vitalistic explanations of biological phenomena in terms of a entelechy or vital principle. In recent years an 'anthropic principle' has received attention in cosmology (Barrow and Tipler, 1986). All such explanations have been condemned by many philosophers an anthropomorphic.
 Nevertheless, philosophers and scientists often maintain that functional explanations play an important an legitimate role in various sciences such as, evolutionary biology, anthropology and sociology. For example, of the peppered moth in Liverpool, the change in colour from the light phase to the dark phase and back again to the light phase provided adaption to a changing environment and fulfilled the function of reducing predation on the spacies. In the study of primitive soviets anthropologists have maintained that various rituals the (rain dance) which may be inefficacious in braining about their manifest gaols (producing rain), actually cohesion at a period of stress (often a drought). Philosophers who admit teleological and/or functional explanations in common sense and science oftentimes take pans to argue that such explanations can be annualized entirely in terms of efficient causes, thereby escaping the charge of anthropomorphism (Wright, 1976): Again, however, not all philosophers agree.
 Causal theories of Propositional knowledge differ over whether they deviate from the tripartite analysis by dropping the requirements that one's believing (accepting) that 'h' be justified. The same variation occurs regarding reliability theories, which present the Knower as reliable concerning the issue of whether or not 'h', in the sense that some of one's cognitive or epistemic states, θ, are such that, given further characteristics of oneself-possibly including relations to factors external to one and which one may not be aware-it is nomologically necessary (or at least probable) that 'h'. In some versions, the reliability is required to be 'global' in as far as it must concern a nomologically (probabilistic-relationship) relationship that states of type θ to the acquisition of true beliefs about a wider range of issues than merely whether or not 'h'. There is also controversy about how to delineate the limits of what constitutes a type of relevant personal state or characteristic. (For example, in a case where Mr. Notgot has not been shamming and one does know thereby that someone in the office owns a Ford, such as a way of forming beliefs about the properties of persons spatially close to one, or instead something narrower, such as a way of forming beliefs about Ford owners in offices partly upon the basis of their relevant testimony?)
 One important variety of reliability theory is a conclusive reason account, which includes a requirement that one's reasons for believing that 'h' be such that in one's circumstances, if h* were not to occur then, e.g., one would not have the reasons one does for believing that 'h', or, e.g., one would not believe that 'h'. Roughly, the latter is demanded by theories that treat a Knower as 'tracking the truth', theories that include the further demand that is roughly, if it were the case, that 'h', then one would believe that 'h'. A version of the tracking theory has been defended by Robert Nozick (1981), who adds that if what he calls a 'method' has been used to arrive at the belief that 'h', then the antecedent clauses of the two conditionals that characterize tracking will need to include the hypothesis that one would employ the very same method.
 But unless more conditions are added to Nozick's analysis, it will be too weak to explain why one lack's knowledge in a version of the last variant of the tricky Mr. Notgot case described above, where we add the following details: (a) Mr. Notgot's compulsion is not easily changed, (b) while in the office, Mr. Notgot has no other easy trick of the relevant type to play on one, and finally for one's belief that 'h', not by reasoning through a false belief ut by basing belief that 'h', upon a true existential generalization of one's evidence.
 Nozick's analysis is in addition too strong to permit anyone ever to know that 'h': 'Some of my beliefs about beliefs might be otherwise, e.g., I might have rejected on of them'. If I know that 'h5' then satisfaction of the antecedent of one of Nozick's conditionals would involve its being false that 'h5', thereby thwarting satisfaction of the consequent's requirement that I not then believe that 'h5'. For the belief that 'h5' is itself one of my beliefs about beliefs (Shope, 1984).
 Some philosophers think that the category of knowing for which is true. Justified believing (accepting) is a requirement constituting only a species of Propositional knowledge, construed as an even broader category. They have proposed various examples of 'PK' that do not satisfy the belief and/ort justification conditions of the tripartite analysis. Such cases are often recognized by analyses of Propositional knowledge in terms of powers, capacities, or abilities. For instance, Alan R. White (1982) treats 'PK' as merely the ability to provide a correct answer to a possible questions, however, White may be equating 'producing' knowledge in the sense of producing 'the correct answer to a possible question' with 'displaying' knowledge in the sense of manifesting knowledge. (White, 1982). The latter can be done even by very young children and some non-human animals independently of their being asked questions, understanding questions, or recognizing answers to questions. Indeed, an example that has been proposed as an instance of knowing that 'h' without believing or accepting that 'h' can be modified so as to illustrate this point. Two examples concerns an imaginary person who has no special training or information about horses or racing, but who in an experiment persistently and correctly picks the winners of upcoming horseraces. If the example is modified so that the hypothetical 'seer' never picks winners but only muses over whether those horses wight win, or only reports those horses winning, this behaviour should be as much of a candidate for the person's manifesting knowledge that the horse in question will win as would be the behaviour of picking it as a winner.
 These considerations expose limitations in Edward Craig's analysis (1990) of the concept of knowing of a person's being a satisfactory informant in relation to an inquirer who wants to find out whether or not 'h'. Craig realizes that counterexamples to his analysis appear to be constituted by Knower who are too recalcitrant to inform the inquirer, or too incapacitate to inform, or too discredited to be worth considering (as with the boy who cried 'Wolf'). Craig admits that this might make preferable some alternative view of knowledge as a different state that helps to explain the presence of the state of being a suitable informant when the latter does obtain. Such the alternate, which offers a recursive definition that concerns one's having the power to proceed in a way representing the state of affairs, causally involved in one's proceeding in this way. When combined with a suitable analysis of representing, this theory of propositional knowledge can be unified with a structurally similar analysis of knowing how to do something.
 Knowledge and belief, according to most epistemologists, knowledge entails belief, so that I cannot know that such and such is the case unless I believe that such and such is the case. Others think this entailment thesis can be rendered more accurately if we substitute for belief some closely related attitude. For instance, several philosophers would prefer to say that knowledge entail psychological certainties (Prichard, 1950 and Ayer, 1956) or conviction (Lehrer, 1974) or acceptance (Lehrer, 1989). None the less, there are arguments against all versions of the thesis that knowledge requires having a belief-like attitude toward the known. These arguments are given by philosophers who think that knowledge and belief (or a facsimile) are mutually incompatible (the incomparability thesis), or by ones who say that knowledge does not entail belief, or vice versa, so that each may exist without the other, but the two may also coexist (the separability thesis).
 The incompatibility thesis is sometimes traced to Plato (429-347 Bc) in view of his claim that knowledge is infallible while belief or opinion is fallible ('Republic' 476-9). But this claim would not support the thesis. Belief might be a component of an infallible form of knowledge in spite of the fallibility of belief. Perhaps, knowledge involves some factor that compensates for the fallibility of belief.
 A. Duncan-Jones (1939: Also Vendler, 1978) cite linguistic evidence to back up the incompatibility thesis. He notes that people often say 'I do not believe she is guilty. I know she is' and the like, which suggest that belief rule out knowledge. However, as Lehrer (1974) indicates, the above exclamation is only a more emphatic way of saying 'I do not just believe she is guilty, I know she is' where 'just' makes it especially clear that the speaker is signalling that she has something more salient than mere belief, not that she has something inconsistent with belief, namely knowledge. Compare: 'You do not hurt him, you killed him.'
 H.A. Prichard (1966) offers a defence of the incompatibility thesis that hinges on the equation of knowledge with certainty (both infallibility and psychological certitude) and the assumption that when we believe in the truth of a claim we are not certain about its truth. Given that belief always involves uncertainty while knowledge never dies, believing something rules out the possibility of knowing it. Unfortunately, however, Prichard gives 'us' no goods reason to grant that states of belief are never ones involving confidence. Conscious beliefs clearly involve some level of confidence, to suggest that we cease to believe things about which we are completely confident is bizarre.
 A.D. Woozley (1953) defends a version of the separability thesis. Woozley's version, which deals with psychological certainty rather than belief per se, is that knowledge can exist in the absence of confidence about the item known, although might also be accompanied by confidence as well. Woozley remarks that the test of whether I know something is 'what I can do, where what I can do may include answering questions.' On the basis of this remark he suggests that even when people are unsure of the truth of a claim, they might know that the claim is true. We unhesitatingly attribute knowledge to people who give correct responses on examinations even if those people show no confidence in their answers. Woozley acknowledges, however, that it would be odd for those who lack confidence to claim knowledge. It would be peculiar to say, I am unsure whether my answer is true: Still, I know it is correct But this tension Woozley explains using a distinction between conditions under which we are justified in making a claim (such as a claim to know something), and conditions under which the claim we make is true. While 'I know such and such' might be true even if I am unsure whether such and such holds, nonetheless it would be inappropriate for me to claim that I know that such and such unless I were sure of the truth of my claim.
 Colin Radford (1966) extends Woozley's defence of the separability thesis. In Radford's view, not only is knowledge compatible with the lack of certainty, it is also compatible with a complete lack of belief. He argues by example. In one example, Jean has forgotten that he learned some English history year's priori and yet he is able to give several correct responses to questions such as 'When did the Battle of Hastings occur?' Since he forgot that he took history, he considers the correct response to be no more than guesses. Thus, when he says that the Battle of Hastings took place in 1066 he would deny having the belief that the Battle of Hastings took place in 1066. A disposition he would deny being responsible (or having the right to be convincing) that 1066 was the correct date. Radford would none the less insist that Jean know when the Battle occurred, since clearly be remembering the correct date. Radford admits that it would be inappropriate for Jean to say that he knew when the Battle of Hastings occurred, but, like Woozley he attributes the impropriety to a fact about when it is and is not appropriate to claim knowledge. When we claim knowledge, we ought, at least to believe that we have the knowledge we claim, or else our behaviour is 'intentionally misleading'.
 Those that agree with Radford's defence of the separability thesis will probably think of belief as an inner state that can be detected through introspection. That Jean lack's beliefs about English history is plausible on this Cartesian picture since Jean does not find himself with any beliefs about English history when ne seek them out. One might criticize Radford, however, by rejecting that Cartesian view of belief. One could argue that some beliefs are thoroughly unconscious, for example. Or one could adopt a behaviourist conception of belief, such as Alexander Bain's (1859), according to which having beliefs is a matter of the way people are disposed to behave (and has not Radford already adopted a behaviourist conception of knowledge?) Since Jean gives the correct response when queried, a form of verbal behaviour, a behaviourist would be tempted to credit him with the belief that the Battle of Hastings occurred in 1066.
 D.M. Armstrong (1873) takes a different tack against Radford. Jean does know that the Battle of Hastings took place in 1066. Armstrong will grant Radfod that point, in fact, Armstrong suggests that Jean believe that 1066 is not the date the Battle of Hastings occurred, for Armstrong equates the belief that such and such is just possible but no more than just possible with the belief that such and such is not the case. However, Armstrong insists, Jean also believes that the Battle did occur in 1066. After all, had Jean been mistaught that the Battle occurred in 1066, and subsequently 'guessed' that it took place in 1066, we would surely describe the situation as one in which Jean's false belief about the Battle became unconscious over time but persisted of a memory trace that was causally responsible for his guess. Out of consistency, we must describe Radford's original case as one that Jean's true belief became unconscious but persisted long enough to cause his guess. Thus, while Jean consciously believes that the Battle did not occur in 1066, unconsciously he does believe it occurred in 1066. So after all, Radford does not have a counterexample to the claim that knowledge entails belief.
 Armstrong's response to Radford was to reject Radford's claim that the examinee lacked the relevant belief about English history. Another response is to argue that the examinee lacks the knowledge Radford attributes to him (cf. Sorenson, 1982). If Armstrong is correct in suggesting that Jean believes both that 1066 is and that it is not the date of the Battle of Hastings, one might deny Jean knowledge on the grounds that people who believe the denial of what they believe cannot be said t know the truth of their belief. Another strategy might be to compare the examine case with examples of ignorance given in recent attacks on externalist accounts of knowledge (needless to say.  Externalists themselves would tend not to favour this strategy). Consider the following case developed by BonJour (1985): For no apparent reason, Samantha believes that she is clairvoyant. Again, for no apparent reason, she one day comes to believe that the President is in New York City, even though she has every reason to believe that the President is in Washington, DC. In fact, Samantha is a completely reliable clairvoyant, and she has arrived at her belief about the whereabouts of the President thorough the power of her clairvoyance. Yet surely Samanthas belief is completely irrational. She is not justified in thinking what she does. If so, then she does not know where the President is. But Radford's examinee is unconventional. Even if Jean lacks the belief that Radford denies him, Radford does not have an example of knowledge that is unattended with belief. Suppose that Jean's memory had been sufficiently powerful to produce the relevant belief. As Radford says, in having every reason to suppose that his response is mere guesswork, and he has every reason to consider his belief false. His belief would be an irrational one, and hence one about whose truth Jean would be ignorant.
 Least has been of mention to an approaching view from which 'perception' basis upon itself as a fundamental philosophical topic both for its central place in ant theory of knowledge, and its central place un any theory of consciousness. Philosophy in this area is constrained by a number of properties that we believe to hold of perception, (1) It gives 'us' knowledge of the world around 'us,' (2) We are conscious of that world by being aware of 'sensible qualities': Colour, sounds, tastes, smells, felt warmth, and the shapes and positions of objects in the environment. (3) Such consciousness is effected through highly complex information channels, such as the output of the three different types of colour-sensitive cells in the eye, or the channels in the ear for interpreting pulses of air pressure as frequencies of sound. (4) There ensues even more complex neurophysiological coding of that information, and eventually higher-order brain functions bring it about that we interpreted the information so received. (Much of this complexity has been revealed by the difficulties of writing programs enabling computers to recognize quite simple aspects of the visual scene.) The problem is to avoid thinking of here being a central, ghostly, conscious self, fed information in the same way that a screen if fed information by a remote television camera. Once such a model is in place, experience will seem like a veil getting between 'us' and the world, and the direct objects of perception will seem to be private items in an inner theatre or sensorium. The difficulty of avoiding this model is epically cute when we considered the secondary qualities of colour, sound, tactile feelings and taste, which can easily seem to have a purely private existence inside the perceiver, like sensation of pain. Calling such supposed items names like 'sense-data' or 'percepts' exacerbates the tendency, but once the model is in place, the first property, that perception gives 'us' knowledge of the world and its surrounding surfaces, is quickly threatened, for there will now seem little connection between these items in immediate experience and any independent reality. Reactions to this problem include 'scepticism' and 'idealism.'
 A more hopeful approach is to claim that the complexities of (3) and (4) explain how we can have direct acquaintance of the world, than suggesting that the acquaintance we do have been at best indirect. It is pointed out that perceptions are not like sensation, precisely because they have a content, or outer-directed nature. To have a perception is to be aware of the world for being such-and-such a way, than to enjoy a mere modification of sensation. But such direct realism has to be sustained in the face of the evident personal (neurophysiological and other) factors determining haw we perceive. One approach is to ask why it is useful to be conscious of what we perceive, when other aspects of our functioning work with information determining responses without any conscious awareness or intervention. A solution to this problem would offer the hope of making consciousness part of the natural world, than a strange optional extra.
 Furthering, perceptual knowledge is knowledge acquired by or through the senses and includes most of what we know. We cross intersections when we see the light turn green, head for the kitchen when we smell the roast burning, squeeze the fruit to determine its ripeness, and climb out of bed when we hear the alarm ring. In each case we come to know something-that the light has turned green, that the roast is burning, that the melon is overripe, and that it is time to get up-by some sensory means. Seeing that the light has turned green is learning something-that the light has turned green-by use of the eyes. Feeling that the melon is overripe is coming to know a fact-that the melon is overripe-by one's sense to touch. In each case the resulting knowledge is somehow based on, derived from or grounded in the sort of experience that characterizes the sense modality in question.
 Much as much of our perceptual knowledge is indirect, dependent or derived. By this I mean that the facts we describe ourselves as learning, as coming to know, by perceptual means are pieces of knowledge that depend on our coming to know something else, some other fact, in a more direct way. We see, by the gauge, that we need gas, see, by the newspapers, that our team has lost again, see, by her expression, that she is nervous. This derived or dependent sort of knowledge is particularly prevalent in the cases of vision, but it occurs, to a lesser degree, in every sense modality. We install bells and other noise-makers so that we calm for example, hear (by the bell) that someone is at the door and (by the alarm) that its time to get up. When we obtain knowledge in this way, it is clear that unless one sees-hence, comes to know something about the gauge (that it says) and (hence, know) that one is described as coming to know by perceptual means. If one cannot hear that the bell is ringing, one cannot-in at least in this way-hear that one's visitors have arrived. In such cases one sees (hears, smells, etc.) that 'a' is 'F', coming to know thereby that 'a' is 'F', by seeing (hearing, etc.) that some other condition, 'b's' being 'G', obtains when this occurs, the knowledge (that 'a' is 'F') is derived from, or dependent on, the more basic perceptual knowledge that 'b' is 'G'.
 And finally, the representational Theory of mind (RTM) (which goes back at least to Aristotle) takes as its starting point commonsense mental states, such as thoughts, beliefs, desires, perceptions and images. Such states are said to have 'intentionality'-they are about or refer to things, and may be evaluated with respect to properties like consistency, truth, appropriateness and accuracy. (For example, the thought that cousins are not related is inconsistent, the belief that Elvis is dead is true, the desire to eat the moon is inappropriate, a visual experience of a ripe strawberry as red is accurate, an image of George W. Bush with dreadlocks is inaccurate.)
 The Representational Theory of Mind, defines such intentional mental states as relations to mental representations, and explains the intentionality of the former in terms of the semantic properties of the latter. For example, to believe that Elvis is dead is to be appropriately related to a mental representation whose propositional content is that Elvis is dead. (The desire that Elvis be dead, the fear that he is dead, the regret that he is dead, etc., involve different relations to the same mental representation.) To perceive a strawberry is to have a sensory experience of some kind which is appropriately related to (e.g., caused by) the strawberry Representational theory of mind also understands mental processes such as thinking, reasoning and imagining as sequences of intentional mental states. For example, to imagine the moon rising over a mountain is to entertain a series of mental images of the moon (and a mountain). To infer a proposition q from the propositions p and if 'p' then 'q' is (among other things) to have a sequence of thoughts of the form 'p', 'if p' then 'q', 'q'.
 Contemporary philosophers of mind have typically supposed (or at least hoped) that the mind can be naturalized-i.e., that all mental facts have explanations in the terms of natural science. This assumption is shared within cognitive science, which attempts to provide accounts of mental states and processes in terms (ultimately) of features of the brain and central nervous system. In the course of doing so, the various sub-disciplines of cognitive science (including cognitive and computational psychology and cognitive and computational neuroscience) postulate a number of different kinds of structures and processes, many of which are not directly implicated by mental states and processes as commonsensical conceived. There remains, however, a shared commitment to the idea that mental states and processes are to be explained in terms of mental representations.
 In philosophy, recent debates about mental representation have centred around the existence of propositional attitudes (beliefs, desires, etc.) and the determination of their contents (how they come to be about what they are about), and the existence of phenomenal properties and their relation to the content of thought and perceptual experience. Within cognitive science itself, the philosophically relevant debates have been focussed on the computational architecture of the brain and central nervous system, and the compatibility of scientific and commonsense accounts of mentality.
 Intentional Realists such as Dretske (e.g., 1988) and Fodor (e.g., 1987) note that the generalizations we apply in everyday life in predicting and explaining each other's behaviour (often collectively referred to as 'folk psychology') are both remarkably successful and indispensable. What a person believes, doubts, desires, fears, etc. is a highly reliable indicator of what that person will do; and we have no other way of making sense of each other's behaviour than by ascribing such states and applying the relevant generalizations. We are thus committed to the basic truth of commonsense psychology and, hence, to the existence of the states its generalizations refer to. (Some realists, such as Fodor, also hold that commonsense psychology will be vindicated by cognitive science, given that propositional attitudes can be construed as computational relations to mental representations.)
 Intentional Eliminativists, such as Churchland, (perhaps) Dennett and (at one time) Stich argue that no such things as propositional attitudes (and their constituent representational states) are implicated by the successful explanation and prediction of our mental lives and behaviour. Churchland denies that the generalizations of commonsense propositional-attitude psychology are true. He (1981) argues that folk psychology is a theory of the mind with a long history of failure and decline, and that it resists incorporation into the framework of modern scientific theories (including cognitive psychology). As such, it is comparable to alchemy and phlogiston theory, and ought to suffer a comparable fate. Commonsense psychology is false, and the states (and representations) it postulates simply don't exist. (It should be noted that Churchland is not an eliminativist about mental representation tout court.
 Dennett (1987) grants that the generalizations of commonsense psychology are true and indispensable, but denies that this is sufficient reason to believe in the entities they appear to refer to. He argues that to give an intentional explanation of a system's behaviour is merely to adopt the 'intentional stance' toward it. If the strategy of assigning contentful states to a system and predicting and explaining its behaviour (on the assumption that it is rational-i.e., that it behaves as it should, given the propositional attitudes it should have in its environment) is successful, then the system is intentional, and the propositional-attitude generalizations we apply to it are true. But there is nothing more to having a propositional attitude than this.
 Though he has been taken to be thus claiming that intentional explanations should be construed instrumentally, Dennett (1991) insists that he is a 'moderate' realist about propositional attitudes, since he believes that the patterns in the behaviour and behavioural dispositions of a system on the basis of which we (truly) attribute intentional states to it are objectively real. In the event that there are two or more explanatorily adequate but substantially different systems of intentional ascriptions to an individual, however, Dennett claims there is no fact of the matter about what the system believes (1987, 1991). This does suggest an irrealism at least with respect to the sorts of things Fodor and Dretske take beliefs to be; though it is not the view that there is simply nothing in the world that makes intentional explanations true.
 (Davidson 1973, 1974 and Lewis 1974 also defend the view that what it is to have a propositional attitude is just to be interpretable in a particular way. It is, however, not entirely clear whether they intend their views to imply irrealism about propositional attitudes.). Stich (1983) argues that cognitive psychology does not (or, in any case, should not) taxonomize mental states by their semantic properties at all, since attribution of psychological states by content is sensitive to factors that render it problematic in the context of a scientific psychology. Cognitive psychology seeks causal explanations of behaviour and cognition, and the causal powers of a mental state are determined by its intrinsic 'structural' or 'syntactic' properties. The semantic properties of a mental state, however, are determined by its extrinsic properties-e.g., its history, environmental or intra-mental relations. Hence, such properties cannot figure in causal-scientific explanations of behaviour. (Fodor 1994 and Dretske 1988 are realist attempts to come to grips with some of these problems.) Stich proposes a syntactic theory of the mind, on which the semantic properties of mental states play no explanatory role.
 It is a traditional assumption among realists about mental representations that representational states come in two basic varieties (Boghossian 1995). There are those, such as thoughts, which are composed of concepts and have no phenomenal ('what-it's-like') features ('qualia'), and those, such as sensory experiences, which have phenomenal features but no conceptual constituents. (Non-conceptual content is usually defined as a kind of content that states of a creature lacking concepts might nonetheless enjoy. On this taxonomy, mental states can represent either in a way analogous to expressions of natural languages or in a way analogous to drawings, paintings, maps or photographs. (Perceptual states such as seeing that something is blue, are sometimes thought of as hybrid states, consisting of, for example, a Non-conceptual sensory experience and a thought, or some more integrated compound of sensory and conceptual components.)
 Some historical discussions of the representational properties of mind (e.g., Aristotle 1984, Locke 1689/1975, Hume 1739/1978) seem to assume that Non-conceptual representations-percepts ('impressions'), images ('ideas') and the like-are the only kinds of mental representations, and that the mind represents the world in virtue of being in states that resemble things in it. On such a view, all representational states have their content in virtue of their phenomenal features. Powerful arguments, however, focussing on the lack of generality (Berkeley 1975), ambiguity (Wittgenstein 1953) and non-compositionality (Fodor 1981) of sensory and imagistic representations, as well as their unsuitability to function as logical (Frége 1918/1997, Geach 1957) or mathematical (Frége 1884/1953) concepts, and the symmetry of resemblance (Goodman 1976), convinced philosophers that no theory of mind can get by with only Non-conceptual representations construed in this way.
 Contemporary disagreement over Non-conceptual representation concerns the existence and nature of phenomenal properties and the role they play in determining the content of sensory experience. Dennett (1988), for example, denies that there are such things as qualia at all; while Brandom (2002), McDowell (1994), Rey (1991) and Sellars (1956) deny that they are needed to explain the content of sensory experience. Among those who accept that experiences have phenomenal content, some (Dretske, Lycan, Tye) argue that it is reducible to a kind of intentional content, while others (Block, Loar, Peacocke) argue that it is irreducible.
 The representationalist thesis is often formulated as the claim that phenomenal properties are representational or intentional. However, this formulation is ambiguous between a reductive and a non-deductive claim (though the term 'representationalism' is most often used for the reductive claim). On one hand, it could mean that the phenomenal content of an experience is a kind of intentional content (the properties it represents). On the other, it could mean that the (irreducible) phenomenal properties of an experience determine an intentional content. Representationalists such as Dretske, Lycan and Tye would assent to the former claim, whereas phenomenalists such as Block, Chalmers, Loar and Peacocke would assent to the latter. (Among phenomenalists, there is further disagreement about whether qualia are intrinsically representational (Loar) or not (Block, Peacocke).
 Most (reductive) representationalists are motivated by the conviction that one or another naturalistic explanation of intentionality is, in broad outline, correct, and by the desire to complete the naturalization of the mental by applying such theories to the problem of phenomenality. (Needless to say, most phenomenalists (Chalmers is the major exception) are just as eager to naturalize the phenomenal-though not in the same way.)
 The main argument for representationalism appeals to the transparency of experience (cf. Tye 2000: 45-51). The properties that characterize what it's like to have a perceptual experience are presented in experience as properties of objects perceived: in attending to an experience, one seems to 'see through it' to the objects and properties it is experiences of. They are not presented as properties of the experience itself. If nonetheless they were properties of the experience, perception would be massively deceptive. But perception is not massively deceptive. According to the representationalist, the phenomenal character of an experience is due to its representing objective, non-experiential properties. (In veridical perception, these properties are locally instantiated; in illusion and hallucination, they are not.) On this view, introspection is indirect perception: one comes to know what phenomenal features one's experience has by coming to know what objective features it represents.
 In order to account for the intuitive differences between conceptual and sensory representations, representationalists appeal to their structural or functional differences. Dretske (1995), for example, distinguishes experiences and thoughts on the basis of the origin and nature of their functions: an experience of a property 'P' is a state of a system whose evolved function is to indicate the presence of 'P' in the environment; a thought representing the property 'P', on the other hand, is a state of a system whose assigned (learned) function is to calibrate the output of the experiential system. Rey (1991) takes both thoughts and experiences to be relations to sentences in the language of thought, and distinguishes them on the basis of (the functional roles of) such sentences' constituent predicates. Lycan (1987, 1996) distinguishes them in terms of their functional-computational profiles. Tye (2000) distinguishes them in terms of their functional roles and the intrinsic structure of their vehicles: thoughts are representations in a language-like medium, whereas experiences are image-like representations consisting of 'symbol-filled arrays.' (the account of mental images in Tye 1991.)
 Phenomenalists tend to make use of the same sorts of features (function, intrinsic structure) in explaining some of the intuitive differences between thoughts and experiences; but they do not suppose that such features exhaust the differences between phenomenal and non-phenomenal representations. For the phenomenalist, it is the phenomenal properties of experiences-qualia themselves-that constitute the fundamental difference between experience and thought. Peacocke (1992), for example, develops the notion of a perceptual 'scenario' (an assignment of phenomenal properties to coordinates of a three-dimensional egocentric space), whose content is 'correct' (a semantic property) if in the corresponding 'scene' (the portion of the external world represented by the scenario) properties are distributed as their phenomenal analogues are in the scenario.
 Another sort of representation championed by phenomenalists (e.g., Block, Chalmers (2003) and Loar (1996)) is the 'phenomenal concept' -, a conceptual/phenomenal hybrid consisting of a phenomenological 'sample' (an image or an occurrent sensation) integrated with (or functioning as) a conceptual component. Phenomenal concepts are postulated to account for the apparent fact (among others) that, as McGinn (1991) puts it, 'you cannot form [introspective] concepts of conscious properties unless you yourself instantiate those properties.' One cannot have a phenomenal concept of a phenomenal property 'P', and, hence, phenomenal beliefs about P, without having experience of 'P', because 'P' itself is (in some way) constitutive of the concept of 'P'. (Jackson 1982, 1986 and Nagel 1974.)
 Though imagery has played an important role in the history of philosophy of mind, the important contemporary literature on it is primarily psychological. In a series of psychological experiments done in the 1970s (summarized in Kosslyn 1980 and Shepard and Cooper 1982), subjects' response time in tasks involving mental manipulation and examination of presented figures was found to vary in proportion to the spatial properties (size, orientation, etc.) of the figures presented. The question of how these experimental results are to be explained has kindled a lively debate on the nature of imagery and imagination.
 Kosslyn (1980) claims that the results suggest that the tasks were accomplished via the examination and manipulation of mental representations that themselves have spatial properties, i.e., pictorial representations, or images. Others, principally Pylyshyn (1979, 1981, 2003), argue that the empirical facts can be explained in terms exclusively of discursive, or propositional representations and cognitive processes defined over them. (Pylyshyn takes such representations to be sentences in a language of thought.)
 The idea that pictorial representations are literally pictures in the head is not taken seriously by proponents of the pictorial view of imagery The claim is, rather, that mental images represent in a way that is relevantly like the way pictures represent. (Attention has been focussed on visual imagery-hence the designation 'pictorial'; though of course there may imagery in other modalities-auditory, olfactory, etc.-as well.)
 The distinction between pictorial and discursive representation can be characterized in terms of the distinction between analog and digital representation (Goodman 1976). This distinction has itself been variously understood (Fodor & Pylyshyn 1981, Goodman 1976, Haugeland 1981, Lewis 1971, McGinn 1989), though a widely accepted construal is that analog representation is continuous (i.e., in virtue of continuously variable properties of the representation), while digital representation is discrete (i.e., in virtue of properties a representation either has or doesn't have) (Dretske 1981). (An analog/digital distinction may also be made with respect to cognitive processes. (Block 1983.)) On this understanding of the analog/digital distinction, imagistic representations, which represent in virtue of properties that may vary continuously (such as being more or less bright, loud, vivid, etc.), would be analog, while conceptual representations, whose properties do not vary continuously (a thought cannot be more or less about Elvis: either it is or it is not) would be digital.
 It might be supposed that the pictorial/discursive distinction is best made in terms of the phenomenal/nonphenomenal distinction, but it is not obvious that this is the case. For one thing, there may be nonphenomenal properties of representations that vary continuously. Moreover, there are ways of understanding pictorial representation that presuppose neither phenomenality nor analogicity. According to Kosslyn (1980, 1982, 1983), a mental representation is 'quasi-pictorial' when every part of the representation corresponds to a part of the object represented, and relative distances between parts of the object represented are preserved among the parts of the representation. But distances between parts of a representation can be defined functionally rather than spatially-for example, in terms of the number of discrete computational steps required to combine stored information about them. (Rey 1981.)
 Tye (1991) proposes a view of images on which they are hybrid representations, consisting both of pictorial and discursive elements. On Tye's account, images are '(labelled) interpreted symbol-filled arrays.' The symbols represent discursively, while their arrangement in arrays has representational significance (the location of each 'cell' in the array represents a specific viewer-centred 2-D location on the surface of the imagined object)
 The contents of mental representations are typically taken to be abstract objects (properties, relations, propositions, sets, etc.). A pressing question, especially for the naturalist, is how mental representations come to have their contents. Here the issue is not how to naturalize content (abstract objects can't be naturalized), but, rather, how to provide a naturalistic account of the content-determining relations between mental representations and the abstract objects they express. There are two basic types of contemporary naturalistic theories of content-determination, causal-informational and functional.
 Causal-informational theories (Dretske 1981, 1988, 1995) hold that the content of a mental representation is grounded in the information it carries about what does (Devitt 1996) or would (Fodor 1987, 1990) cause it to occur. There is, however, widespread agreement that causal-informational relations are not sufficient to determine the content of mental representations. Such relations are common, but representation is not. Tree trunks, smoke, thermostats and ringing telephones carry information about what they are causally related to, but they do not represent (in the relevant sense) what they carry information about. Further, a representation can be caused by something it does not represent, and can represent something that has not caused it.
 The main attempts to specify what makes a causal-informational state a mental representation are Asymmetric Dependency Theories (e.g., Fodor 1987, 1990, 1994) and Teleological Theories (Fodor 1990, Millikan 1984, Papineau 1987, Dretske 1988, 1995). The Asymmetric Dependency Theory distinguishes merely informational relations from representational relations on the basis of their higher-order relations to each other: informational relations depend upon representational relations, but not vice-versa. For example, if tokens of a mental state type are reliably caused by horses, cows-on-dark-nights, zebras-in-the-mist and Great Danes, then they carry information about horses, etc. If, however, such tokens are caused by cows-on-dark-nights, etc. because they were caused by horses, but not vice versa, then they represent horses.
 According to Teleological Theories, representational relations are those a representation-producing mechanism has the selected (by evolution or learning) function of establishing. For example, zebra-caused horse-representations do not mean zebra, because the mechanism by which such tokens are produced has the selected function of indicating horses, not zebras. The horse-representation-producing mechanism that responds to zebras is malfunctioning.
 Functional theories (Block 1986, Harman 1973), hold that the content of a mental representation is grounded in its (causal computational, inferential) relations to other mental representations. They differ on whether relata should include all other mental representations or only some of them, and on whether to include external states of affairs. The view that the content of a mental representation is determined by its inferential/computational relations with all other representations is holism; the view it is determined by relations to only some other mental states is localism (or molecularism). (The view that the content of a mental state depends on none of its relations to other mental states is atomism.) Functional theories that recognize no content-determining external relata have been called solipsistic (Harman 1987). Some theorists posit distinct roles for internal and external connections, the former determining semantic properties analogous to sense, the latter determining semantic properties analogous to reference (McGinn 1982, Sterelny 1989)
 (Reductive) representationalists (Dretske, Lycan, Tye) usually take one or another of these theories to provide an explanation of the (Non-conceptual) content of experiential states. They thus tend to be Externalists (see the next section) about phenomenological as well as conceptual content. Phenomenalists and non-deductive representationalists (Block, Chalmers, Loar, Peacocke, Siewert), on the other hand, take it that the representational content of such states is (at least in part) determined by their intrinsic phenomenal properties. Further, those who advocate a phenomenology-based approach to conceptual content (Horgan and Tiensen, Loar, Pitt, Searle, Siewert) also seem to be committed to internalist individuation of the content (if not the reference) of such states.
 Generally, those who, like informational theorists, think relations to one's (natural or social) environment are (at least partially) determinative of the content of mental representations are Externalists (e.g., Burge 1979, 1986, McGinn 1977, Putnam 1975), whereas those who, like some proponents of functional theories, think representational content is determined by an individual's intrinsic properties alone, are internalists (or individualists; cf. Putnam 1975, Fodor 1981)
 This issue is widely taken to be of central importance, since psychological explanation, whether commonsense or scientific, is supposed to be both causal and content-based. (Beliefs and desires cause the behaviours they do because they have the contents they do. For example, the desire that one have a beer and the beliefs that there is beer in the refrigerator and that the refrigerator is in the kitchen may explain one's getting up and going to the kitchen.) If, however, a mental representation's having a particular content is due to factors extrinsic to it, it is unclear how its having that content could determine its causal powers, which, arguably, must be intrinsic. Some who accept the standard arguments for externalism have argued that internal factors determine a component of the content of a mental representation. They say that mental representations have both 'narrow' content (determined by intrinsic factors) and 'wide' or 'broad' content (determined by narrow content plus extrinsic factors). (This distinction may be applied to the sub-personal representations of cognitive science as well as to those of commonsense psychology.
 Narrow content has been variously construed. Putnam (1975), Fodor (1982)), and Block (1986), for example, seem to understand it as something like dedictorial content (i.e., Frégean sense, or perhaps character, à la Kaplan 1989). On this construal, narrow content is context-independent and directly expressible. Fodor (1987) and Block (1986), however, have also characterized narrow content as radically inexpressible. On this construal, narrow content is a kind of proto-content, or content-determinant, and can be specified only indirectly, via specifications of context/wide-content pairings. On both construal, narrow contents are characterized as functions from context to (wide) content. The narrow content of a representation is determined by properties intrinsic to it or its possessor such as its syntactic structure or its intra-mental computational or inferential role (or its phenomenology.
 Burge (1986) has argued that causation-based worries about externalist individuation of psychological content, and the introduction of the narrow notion, are misguided. Fodor (1994, 1998) has more recently urged that a scientific psychology might not need narrow content in order to supply naturalistic (causal) explanations of human cognition and action, since the sorts of cases they were introduced to handle, viz., Twin-Earth cases and Frége cases, are either nomologically impossible or dismissible as exceptions to non-strict psychological laws.
 The leading contemporary version of the Representational Theory of Mind, the Computational Theory of Mind (CTM), claims that the brain is a kind of computer and that mental processes are computations. According to the computational theory of mind, cognitive states are constituted by computational relations to mental representations of various kinds, and cognitive processes are sequences of such states. The computational theory of mind and the representational theory of mind, may by attempting to explain all psychological states and processes in terms of mental representation. In the course of constructing detailed empirical theories of human and animal cognition and developing models of cognitive processes implementable in artificial information processing systems, cognitive scientists have proposed a variety of types of mental representations. While some of these may be suited to be mental relata of commonsense psychological states, some-so-called 'subpersonal' or 'sub-doxastic' representations-are not. Though many philosophers believe that computational theory of mind can provide the best scientific explanations of cognition and behaviour, there is disagreement over whether such explanations will vindicate the commonsense psychological explanations of prescientific representational theory of mind.
 According to Stich's (1983) Syntactic Theory of Mind, for example, computational theories of psychological states should concern themselves only with the formal properties of the objects those states are relations to. Commitment to the explanatory relevance of content, however, is for most cognitive scientists fundamental (Fodor 1981, Pylyshyn 1984, Von Eckardt 1993). That mental processes are computations, which computations are rule-governed sequences of semantically evaluable objects, and that the rules apply to the symbols in virtue of their content, are central tenets of mainstream cognitive science.
 Explanations in cognitive science appeal to a many different kinds of mental representation, including, for example, the 'mental models' of Johnson-Laird 1983, the 'retinal arrays,' 'primal sketches' and '2½ -D sketches' of Marr 1982, the 'frames' of Minsky 1974, the 'sub-symbolic' structures of Smolensky 1989, the 'quasi-pictures' of Kosslyn 1980, and the 'interpreted symbol-filled arrays' of Tye 1991-in addition to representations that may be appropriate to the explanation of commonsense psychological states. Computational explanations have been offered of, among other mental phenomena, belief (Fodor 1975, Field 1978), visual perception (Marr 1982, Osherson, et al. 1990), rationality (Newell and Simon 1972, Fodor 1975, Johnson-Laird and Wason 1977), language learning and  (Chomsky 1965, Pinker 1989), and musical comprehension (Lerdahl and Jackendoff 1983).
 The classicists (e.g., Turing 1950, Fodor 1975, Fodor and Pylyshyn 1988, Marr 1982, Newell and Simon 1976) hold that mental representations are symbolic structures, which typically have semantically evaluable constituents, and that mental processes are rule-governed manipulations of them that are sensitive to their constituent structure. The connectionists (e.g., McCulloch & Pitts 1943, Rumelhart 1989, Rumelhart and McClelland 1986, Smolensky 1988) hold that mental representations are realized by patterns of activation in a network of simple processors ('nodes') and that mental processes consist of the spreading activation of such patterns. The nodes themselves are, typically, not taken to be semantically evaluable; nor do the patterns have semantically evaluable constituents. (Though there are versions of Connectionism -, 'localist' versions-on which individual nodes are taken to have semantic properties (e.g., Ballard 1986, Ballard & Hayes 1984).) It is arguable, however, that localist theories are neither definitive nor representative of the Conceptionist program (Smolensky 1988, 1991, Chalmers 1993).
 Classicists are motivated (in part) by properties thought seems to share with language. Fodor's Language of Thought Hypothesis (LOTH) (Fodor 1975, 1987), according to which the system of mental symbols constituting the neural basis of thought is structured like a language, provides a well-worked-out version of the classical approach as applied to commonsense psychology. According to the language of thought hypothesis, the potential infinity of complex representational mental states is generated from a finite stock of primitive representational states, in accordance with recursive formation rules. This combinatorial structure accounts for the properties of productivity and systematicity of the system of mental representations. As in the case of symbolic languages, including natural languages (though Fodor does not suppose either that the language of thought hypothesis explains only linguistic capacities or that only verbal creatures have this sort of cognitive architecture), these properties of thought are explained by appeal to the content of the representational units and their combinability into contentful complexes. That is, the semantics of both language and thought is compositional: the content of a complex representation is determined by the contents of its constituents and their structural configuration.
 Connectionists are motivated mainly by a consideration of the architecture of the brain, which apparently consists of layered networks of interconnected neurons. They argue that this sort of architecture is unsuited to carrying out classical serial computations. For one thing, processing in the brain is typically massively parallel. In addition, the elements whose manipulation drives computation in Conceptionist networks (principally, the connections between nodes) are neither semantically compositional nor semantically evaluable, as they are on the classical approach. This contrast with classical computationalism is often characterized by saying that representation is, with respect to computation, distributed as opposed to local: representation is local if it is computationally basic; and distributed if it is not. (Another way of putting this is to say that for classicists mental representations are computationally atomic, whereas for connectionists they are not.)
 Moreover, connectionists argue that information processing as it occurs in Conceptionist networks more closely resembles some features of actual human cognitive functioning. For example, whereas on the classical view learning involves something like hypothesis formation and testing (Fodor 1981), on the Conceptionist model it is a matter of evolving distribution of 'weight' (strength) on the connections between nodes, and typically does not involve the formulation of hypotheses regarding the identity conditions for the objects of knowledge. The Conceptionist network is 'trained up' by repeated exposure to the objects it is to learn to distinguish; and, though networks typically require many more exposures to the objects than do humans, this seems to model at least one feature of this type of human learning quite well.
 Further, degradation in the performance of such networks in response to damage is gradual, not sudden as in the case of a classical information processor, and hence more accurately models the loss of human cognitive function as it typically occurs in response to brain damage. It is also sometimes claimed that Conceptionist systems show the kind of flexibility in response to novel situations typical of human cognition-situations in which classical systems are relatively 'brittle' or 'fragile.'
 Some philosophers have maintained that Connectionism entails that there are no propositional attitudes. Ramsey, Stich and Garon (1990) have argued that if Conceptionist models of cognition are basically correct, then there are no discrete representational states as conceived in ordinary commonsense psychology and classical cognitive science. Others, however (e.g., Smolensky 1989), hold that certain types of higher-level patterns of activity in a neural network may be roughly identified with the representational states of commonsense psychology. Still others (e.g., Fodor & Pylyshyn 1988, Heil 1991, Horgan and Tienson 1996) argue that language-of-thought style representation is both necessary in general and realizable within Conceptionist architectures. (MacDonald & MacDonald 1995 collects the central contemporary papers in the classicist/Conceptionist debate, and provides useful introductory material as well.
 Whereas Stich (1983) accepts that mental processes are computational, but denies that computations are sequences of mental representations, others accept the notion of mental representation, but deny that computational theory of mind provides the correct account of mental states and processes.
 Van Gelder (1995) denies that psychological processes are computational. He argues that cognitive systems are dynamic, and that cognitive states are not relations to mental symbols, but quantifiable states of a complex system consisting of (in the case of human beings) a nervous system, a body and the environment in which they are embedded. Cognitive processes are not rule-governed sequences of discrete symbolic states, but continuous, evolving total states of dynamic systems determined by continuous, simultaneous and mutually determining states of the systems components. Representation in a dynamic system is essentially information-theoretic, though the bearers of information are not symbols, but state variables or parameters.
 Horst (1996), on the other hand, argues that though computational models may be useful in scientific psychology, they are of no help in achieving a philosophical understanding of the intentionality of commonsense mental states. computational theory of mind attempts to reduce the intentionality of such states to the intentionality of the mental symbols they are relations to. But, Horst claims, the relevant notion of symbolic content is essentially bound up with the notions of convention and intention. So the computational theory of mind involves itself in a vicious circularity: the very properties that are supposed to be reduced are (tacitly) appealed to in the reduction.
 To say that a mental object has semantic properties is, paradigmatically, to say that it may be about, or be true or false of, an object or objects, or that it may be true or false simpliciter. Suppose I think that you took to sniffing snuff. I am thinking about you, and if what I think of you (that they take snuff) is true of you, then my thought is true. According to representational theory of mind such states are to be explained as relations between agents and mental representations. To think that you take snuff is to token in some way a mental representation whose content is that ocelots take snuff. On this view, the semantic properties of mental states are the semantic properties of the representations they are relations to.
 Linguistic acts seem to share such properties with mental states. Suppose I say that you take snuff. I am talking about you, and if what I say of you (that they take snuff) is true of them, then my utterance is true. Now, to say that you take snuff is (in part) to utter a sentence that means that you take snuff. Many philosophers have thought that the semantic properties of linguistic expressions are inherited from the intentional mental states they are conventionally used to express (Grice 1957, Fodor 1978, Schiffer 1972/1988, Searle 1983). On this view, the semantic properties of linguistic expressions are the semantic properties of the representations that are the mental relata of the states they are conventionally used to express.
 It is also widely held that in addition to having such properties as reference, truth-conditions and truth-so-called extensional properties-expressions of natural languages also have intensional properties, in virtue of expressing properties or propositions-i.e., in virtue of having meanings or senses, where two expressions may have the same reference, truth-conditions or truth value, yet express different properties or propositions (Frége 1892/1997). If the semantic properties of natural-language expressions are inherited from the thoughts and concepts they express (or vice versa, or both), then an analogous distinction may be appropriate for mental representations.
Theories of representational content may be classified according to whether they are atomistic or holistic and according to whether they are externalistic or internalistic, whereby, emphasizing the priority of a whole over its parts. Furthermore, in the philosophy of language, this becomes the claim that the meaning of an individual word or sentence can only be understood in terms of its relation to an indefinitely larger body of language, such as a whole theory, or even a whole language or form of life. In the philosophy of mind a mental state similarly may be identified only in terms of its relations with others. Moderate holism may allow the other things besides these relationships also count; extreme holism would hold that a network of relationships is all that we have. A holistic view of science holds that experience only confirms or disconfirms large bodies of doctrine, impinging at the edges, and leaving some leeway over the adjustment that it requires.
 Once, again, in the philosophy of mind and language, the view that what is thought, or said, or experienced, is essentially dependent on aspects of the world external to the mind of the subject. The view goes beyond holding that such mental states are typically caused by external factors, to insist that they could not have existed as they now do without the subject being embedded in an external world of a certain kind. It is these external relations that make up the essence or identify of the mental state. Externalism is thus opposed to the Cartesian separation of the mental from the physical, since that holds that the mental could in principle exist as it does even if there were no external world at all. Various external factors have been advanced as ones on which mental content depends, including the usage of experts, the linguistic, norms of the community. And the general causal relationships of the subject. In the theory of knowledge, externalism is the view that a person might know something by being suitably situated with respect to it, without that relationship being in any sense within his purview. The person might, for example, be very reliable in some respect without believing that he is. The view allows that you can know without being justified in believing that you know.
 However, atomistic theories take a representation’s content to be something that can be specified independent entity of that representation’ s relations to other representations. What the American philosopher of mind, Jerry Alan Fodor (1935-) calls the crude causal theory, for example, takes a representation to be a |cow|-a menial representation with the same content as the word ‘cow’-if its tokens are caused by instantiations of the property of being-a-cow, and this is a condition that places no explicit constraints on how |cow|’s must or might relate to other representations. Holistic theories contrasted with atomistic theories in taking the relations a representation bears to others to be essential to its content. According to functional role theories, a representation is a |cow| if it behaves like a |cow| should behave in inference.
 Internalist theories take the content of a representation to be a matter determined by factors internal to the system that uses it. Thus, what Block (1986) calls ‘short-armed’ functional role theories are internalist. Externalist theories take the content of a representation to be determined, in part at least, by factors external to the system that uses it. Covariance theories, as well as telelogical theories that invoke an historical theory of functions, take content to be determined by ‘external’ factors. Crossing the atomist-holistic distinction with the internalist-externalist distinction.
 Externalist theories (sometimes called non-individualistic theories) have the consequence that molecule for molecule identical cognitive systems might yet harbour representations with different contents. This has given rise to a controversy concerning ‘narrow’ content. If we assume some form of externalist theory is correct, then content is, in the first instance ‘wide’ content, i.e., determined in part by factors external to the representing system. On the other hand, it seems clear that, on plausible assumptions about how to individuate psychological capacities, internally equivalent systems must have the same psychological capacities. Hence, it would appear that wide content cannot be relevant to characterizing psychological equivalence. Since cognitive science generally assumes that content is relevant to characterizing psychological equivalence, philosophers attracted to externalist theories of content have sometimes attempted to introduce ‘narrow’ content, i.e., an aspect or kind of content that is equivalent internally equivalent systems. The simplest such theory is Fodor’s idea (1987) that narrow content is a function from contents (i.e., from whatever the external factors are) to wide contents.
 All the same, what a person expresses by a sentence is often a function of the environment in which he or she is placed. For example, the disease I refer to by the term like ‘arthritis’, or the kind of tree I refer to as a ‘Maple’ will be defined by criteria of which I know next to nothing. This raises the possibility of imagining two persons in rather different environments, but in which everything appears the same to each of them. The wide content of their thoughts and sayings will be different if the situation surrounding them is appropriately different: ‘situation’ may include the actual objects they perceive or the chemical or physical kinds of object in the world they inhabit, or the history of their words, or the decisions of authorities on what counts as an example, of one of the terms they use. The narrow content is that part of their thought which remains identical, through their identity of the way things appear, regardless of these differences of surroundings. Partisans of wide content may doubt whether any content in this sense narrow, partisans of narrow content believer that it is the fundamental notion, with wide content being explicable in terms of narrow content plus context.
 Even so, the distinction between facts and values has outgrown its name: it applies not only to matters of fact vs, matters of value, but also to statements that something is, vs. statements that something ought to be. Roughly, factual statements-‘is statements’ in the relevant sense-represent some state of affairs as obtaining, whereas normative statements-evaluative, and deontic ones-attribute goodness to something, or ascribe, to an agent, an obligation to act. Neither distinction is merely linguistic. Specifying a book’s monetary value is making a factual statement, though it attributes a kind of value. ‘That is a good book’ expresses a value judgement though the term ‘value’ is absent (nor would ‘valuable’ be synonymous with ‘good’). Similarly, ‘we are morally obligated to fight’ superficially expresses a statement, and ‘By all indications it ough to rain’ makes a kind of ought-claim; but the former is an ought-statement, the latter an (epistemic) is-statement.
 Theoretical difficulties also beset the distinction. Some have absorbed values into facts holding that all value is instrumental, roughly, to have value is to contribute-in a factual analysable way-to something further which is (say) deemed desirable. Others have suffused facts with values, arguing that facts (and observations) are ‘theory-impregnated’ and contending that values are inescapable to theoretical choice. But while some philosophers doubt that fact/value distinctions can be sustained, there persists a sense of a deep difference between evaluating, or attributing an obligation and, on the other hand, saying how the world is.
 Fact/value distinctions, may be defended by appeal to the notion of intrinsic value, value a thing has in itself and thus independently of its consequences. Roughly, a value statement (proper) is an ascription of intrinsic value, one to the effect that a thing is to some degree good in itself. This leaves open whether ought-statements are implicitly value statements, but even if they imply that something has intrinsic value-e.g., moral value-they can be independently characterized, say by appeal to rules that provide (justifying) reasons for action. One might also ground the fact value distinction in the attributional (or even motivational) component apparently implied by the making of valuational or deontic judgements: Thus, ‘it is a good book, but that is no reason for a positive attribute towards it’ and ‘you ought to do it, but there is no reason to’ seem inadmissible, whereas, substituting, ‘an expensive book’ and ‘you will do it’ yields permissible judgements. One might also argue that factual judgements are the kind which are in principle appraisable scientifically, and thereby anchor the distinction on the factual side. This ligne is plausible, but there is controversy over whether scientific procedures are ‘value-free’ in the required way.
 Philosophers differ regarding the sense, if any, in which epistemology is normative (roughly, valuational). But what precisely is at stake in this controversy is no clearly than the problematic fact/value distinction itself. Must epistemologists as such make judgements of value or epistemic responsibility? If epistemology is naturalizable, then even epistemic principles simply articulate under what conditions-say, appropriate perceptual stimulations-a belief is justified, or constitutes knowledge. Its standards of justification, then would be like standards of, e.g., resilience for bridges. It is not obvious, however, that there appropriate standards can be established without independent judgements that, say, a certain kind of evidence is good enough for justified belief (or knowledge). The most plausible view may be that justification is like intrinsic goodness, though it supervenes on natural properties, it cannot be analysed wholly in factual statements.
 Thus far, belief has been depicted as being all-or-nothing, however, as a resulting causality for which we have grounds for thinking it true, and, all the same, its acceptance is governed by epistemic norms, and, least of mention, it is partially subject to voluntary control and has functional affinities to belief. Still, the notion of acceptance, like that of degrees of belief, merely extends the standard picture, and does not replace it.
 Traditionally, belief has been of epistemological interest in its propositional guise: ‘S’ believes that ‘p’, where ‘p’ is a reposition towards which an agent, ‘S’ exhibits an attitude of acceptance. Not all belief is of this sort. If I trust you to say, I believer you. And someone may believer in Mr. Notgot, or in a free-market economy, or in God. It is sometimes supposed that all belief is ‘reducible’ to propositional belief, belief-that. Thus, my believing you might be thought a matter of my believing, is,  perhaps, that what you say is true, and your belief in free markets or God, is a matter of your believing that free-market economies are desirable or that God exists.
 Some philosophers have followed St, Thomas Aquinas (1225-74), in supposing that to believer in God is simply to believer that certain truths hold while others argue that belief-in is a distinctive attitude, on that includes essentially an element of trust. More commonly, belief-in has been taken to involve a combination of propositional belief together with some further attitude.
 The moral philosopher Richard Price (1723-91) defends the claim that there are different sorts of belief-in, some, but not all reducible to beliefs-that. If you believer in God, you believer that God exists, that God is good, you believer that God is good, etc. But according to Price, your belief involves, in addition, a certain complex pro-attitude toward its object. Even so, belief-in outruns the evidence for the corresponding belief-that. Does this diminish its rationality? If belief-in presupposes believes-that, it might be thought that the evidential standards for the former must be, at least, as high as standards for the latter. And any additional pro-attitude might be thought to require a further layer of justification not required for cases of belief-that.
 Belief-in may be, in general, less susceptible to alternations in the face of unfavourable evidence than belief-that. A believe who encounters evidence against God’s existence may remain unshaken in his belief, in part because the evidence does not bear on his pro-attitude. So long as this ids united with his belief that God exists, the reasonably so-in a way that an ordinary propositional belief that would not.
 The correlative way of elaborating on the general objection to justificatory externalism challenges the sufficiency of the various externalist conditions by citing cases where those conditions are satisfied, but where the believers in question seem intuitively not to be justified. In this context, the most widely discussed examples have to do with possible occult cognitive capacities, like clairvoyance. Considering the point in application once, again, to reliabilism, the claim is that to think that he has such a cognitive power, and, perhaps, even good reasons to the contrary, is not rational or responsible and therefore not epistemically justified in accepting the belief that result from his clairvoyance, dispite the fact that the reliablist condition is satisfied.
 One sort of response to this latter sorts of objection is to ‘bite the bullet’ and insist that such believers are in fact justified, dismissing the seeming intuitions to the contrary as latent internalist prejudice. A more widely adopted response attempts to impose additional conditions, usually of a roughly internalist sort, which will rule out the offending example, while stopping far of a full internalism. But, while there is little doubt that such modified versions of externalism can handle particular cases, as well enough to avoid clear intuitive implausibility, the usually problematic cases that they cannot handle, and also whether there is and clear motivation for the additional requirements other than the general internalist view of justification that externalist are committed to reject.
 A view in this same general vein, one that might be described as a hybrid of internalism and externalism holds that epistemic justification requires that there is a justicatory factor that is cognitively accessible to the believer in question (though it need not be actually grasped), thus ruling out, e.g., a pure reliabilism. At the same time, however, though it must be objectively true that beliefs for which such a factor is available are likely to be true, in addition, the fact need not be in any way grasped or cognitively accessible to the believer. In effect, of the premises needed to argue that a particular belief is likely to be true, one must be accessible in a way that would satisfy at least weak internalism, the internalist will respond that this hybrid view is of no help at all in meeting the objection and has no belief nor is it held in the rational, responsible way that justification intuitively seems to require, for the believer in question, lacking one crucial premise, still has no reason at all for thinking that his belief is likely to be true.
 An alternative to giving an externalist account of epistemic justification, one which may be more defensible while still accommodating many of the same motivating concerns, is to give an externalist account of knowledge directly, without relying on an intermediate account of justification. Such a view will obviously have to reject the justified true belief account of knowledge, holding instead that knowledge is true belief which satisfies the chosen externalist condition, e.g., a result of a reliable process (and perhaps, further conditions as well). This makes it possible for such a view to retain internalist account of epistemic justification, though the centrality of that concept to epistemology would obviously be seriously diminished.
 Such an externalist account of knowledge can accommodate the commonsense conviction that animals, young children, and unsophisticated adults posses knowledge, though not the weaker conviction (if such a conviction does exists) that such individuals are epistemically justified in their beliefs. It is also at least less vulnerable to internalist counter-examples of the sort discussed, since the intuitions involved there pertain more clearly to justification than to knowledge. What is uncertain is what ultimate philosophical significance the resulting conception of knowledge is supposed to have. In particular, does it have any serious bearing on traditional epistemological problems and on the deepest and most troubling versions of scepticism, which seems in fact to be primarily concerned with justification, and knowledge?`
 A rather different use of the terms ‘internalism’ and ‘externalism’ has to do with the issue of how the content of beliefs and thoughts is determined: According to an internalist view of content, the content of such intention states depends only on the non-relational, internal properties of the individual’s mind or grain, and not at all on his physical and social environment: While according to an externalist view, content is significantly affected by such external factors and suggests a view that appears of both internal and external elements is standardly classified as an external view.
 As with justification and knowledge, the traditional view of content has been strongly internalist in character. The main argument for externalism derives from the philosophy y of language, more specifically from the various phenomena pertaining to natural kind terms, indexicals, etc. that motivate the views that have come to be known as ‘direct reference’ theories. Such phenomena seem at least to show that the belief or thought content that can be properly attributed to a person is dependant on facts about his environment-e.g., whether he is on Earth or Twin Earth, what is fact pointing at, the classificatory criteria employed by expects in his social group, etc.-not just on what is going on internally in his mind or brain
 The internalist requirement of cognitive accessibility can be interpreted in at least two ways: A strong version of internalism required that the believer actually be aware of the justifying factor in order to be justified: While a weaker version would require only that he be capable of becoming aware of them by focussing his attention appropriately, but without the need for any change of position, new information etc. Though the phrase ‘cognitively accessible’ suggests the weak for internalism, wherefore, the idea that epistemic justification requires that the believer actually have in his cognitive possession a reason for thinking that the belief is true.
 It should be carefully noticed that when internalism is construed by either that the justifying factors literally are internal mental states of the person or that the internalism. On whether actual awareness of the justifying elements or only the capacity to become aware of them is required, comparatively, the consistency and usually through a common conformity brings upon some coherentists views that could also be internalist, if both the belief and other states with which a justification belief is required to cohere and the coherence relations themselves are reflectively accessible. In spite of its apparency, it is necessary, because on at least some views, e.g., a direct realist view of perception, something other than a mental state of the believer can be cognitively accessible, not sufficient, because there are views according to which at least, some mental states need not be actual (strong versions) or even possible (weak versions) objects of cognitive awareness.
 Obviously too, a view that was externalist in relation to a strong version of internalism (by not requiring that the believer actually be aware of all justifying factors) could still be internalist in relation to a weak version (by requiring that, at least, be capable of becoming aware of them).
 The most prominent recent externalist views have been versions of ‘reliabilism’, whose main requirement for justification is roughly that the beliefs are produced in a way or  to a considerable degree in which of subject matter conducting a process that makes of objectively likely that the belief is true. What makes such a view externalist is the absence of any requirement that the person for whom the belief is justified have any sort of cognitive access to the relation of reliability in question. Lacking such access, such a person will in general have no reason for thinking that the belief is true or likely to be true, but will, on such an account, nonetheless, be epistemically justified in accepting it. Thus, such a view arguably marks a major break from the modern epistemological tradition, stemming from Descartes, which identifies epistemic justification with having a reason, perhaps, even a conclusive reason, for thinking that the belief is true. An epistemologist working within this tradition is likely to feel that the externalist, than offering a competing account of the same concept of epistemic justification with which the traditional epistemologist is concerned, has simply changed the subject.
 An alterative to giving an externalist account of epistemic justification, one which may be more defensible while still accommodating many of the same motivating concerns, is especially given to some externalists account of knowledge directly, without relying on an intermediate account of justification. Such a view will obviously have to reject the justified true belief account of knowledge, holding instead that knowledge is true belief which satisfies the chosen externalist condition, e.g., is a result of a reliable process, and, perhaps, further conditions as well. This makes it possible for such a view to retain an internalist account of epistemic justification, though the centralities are seriously diminished. Such an externalist account of knowledge can accommodate the common-sense conviction that animals, young children and unsophisticated adults possess knowledge though not the weaker conviction that such individuals are epistemically justified in their belief. It is also, at least. Vulnerable to internalist counter-examples, since the intuitions involved there pertains more clearly to justification than to knowledge, least of mention, as with justification and knowledge, the traditional view of content has been strongly internalist in character. An objection to externalist accounts of content is that they seem unable to do justice to our ability to know the content of our beliefs or thoughts ‘from the inside’, simply by reflection. So, then, the adoption of an externalist account of mental content would seem as if part of all of the content of a belief is inaccessible to the believer, then both the justifying status of other beliefs in relation to that content and the status of the content as justifying further beliefs will be similarly inaccessible, thus contravening the internalist requirements for justification.
 Externalists, however, argue that the indirect knowledge that ‘a’ is ‘F’, though it may depend on the knowledge that ‘b’ is ‘G’, does not require knowledge of the connecting fact, the fact that ‘a’ is ‘F’ when ‘b’ is ‘G’. Simple belief (or, perhaps, justified belief, there is stronger and weaker versions of externalism) in the connecting fact is sufficient to confer a knowledge of the fact is sufficient to confer a knowledge e of the connected fact. Even if, strictly speaking, I don’t know she is nervous whenever she fidgets like that, I can nonetheless, see and hence know, that she is nervous by the way she fidgets, if I (correctly) assume that his behaviour r is a reliable expression of nervousness. One need not know the gauge is working well to make observations (acquire observational knowledge) with it. All that is required, besides the observer believing that the gauge is reliable, is that the gauge, in fact, be reliable, i.e., that the observer’s background beliefs be true. Critics of externalisms have been quick to point out that this theory has the unpalatable consequence that knowledge can be made possible by - and, in this sense, be made to rest on - lucky hunches (that turn out true) and unsupported (even irrational) beliefs. Surely, internalist argues, if one is going t o know that ‘a’ is ‘F’ on the basis of b’s being ‘G’, one should have (as a bare minimum) some justification for thinking that ‘a’ is ‘F’, or is probably ‘F’, when ‘b’ is ‘G’.
 Whatever view one takes about these matters (with the possible exception of extreme externalism) indirect perception obviously requires some understanding (knowledge? Justification? Belief?) of the general relationship between the fact one comes to know (that ‘a’ is ‘F’) and the facts (that ‘b’ is ‘G’) that enable one to know it. And it is this requirement on background knowledge or understanding that leads to questions to questions about the possibility of indirect perceptual knowledge. Is it really knowledge? The first question is inspired by sceptical doubts about whether we can ever know the connecting facts in question. How is it possible to learn, to acquire knowledge of, the connecting fact’s knowledge of which is necessary to see? By b’s being ‘G’, and that ‘a’ is ‘F’? These connecting facts do not appear to be perceptually knowable. Quite the contrary, they appear to b e general truths knowable (if knowable at all) by inductive inference e from past observations. And if one is sceptical about obtaining knowledge in this indirect, inductive way one is, perforce, sceptical about the existence of the kind of indirect knowledge, including indirect perceptual knowledge of the set described, in that depends on it.
 Even if one puts aside such sceptical questions, however, they’re remains a legitimate concern about the perceptual character of this kind knowledge. If one sees that ‘a’ is ‘F’ by seeing that ‘b’ is ‘G’, is really seeing that ‘a’ is ‘F’? Isn’t perception merely a part - and, from an epistemological standpoint, the less significant part - of the process whereby one comes to know that ‘a’ is ‘F?’. One must, it is true, sere that ‘b’ is ‘G’, but this is only one of the premises needed to reach the conclusion (knowledge) that ‘a’ is ‘F’. There is also the background knowledge that is essential to the process. If we think of a theory as any factual proposition, or set of factual propositions, that cannot itself be known in some direct observational way, we can express this worry by saying that indirect perception is always theory-loaded: Seeing (indirectly)that ‘a’ is ‘F’ is only possible if the observer already has knowledge of (justification for, belief in) some theory, the theory ‘connecting’ the fast one cannot come to know (that ‘a’ is ‘F’) with the fact (that ‘b’ is ‘G’) that enables one to know it.
 This, of course, reverses the standard foundationalist picture of human knowledge. Instead of theoretical knowledge depending on, and being derived from, perception, perception (of the indirect sort) presupposes a prior knowledge.
 Foundationalists are quick to point out that this apparent reversal in the structure of human knowledge is only apparent. Our indirect perception of facts depends on theory, yes, but this merely shows that indirect perceptual knowledge is not part of the foundation. To reach the kind of perceptual knowledge that lies at the foundation, we need to look at a form of perception that is purified of all theoretical elements. This then, will be perceptual knowledge pure and direct. No background knowledge or assumptions about connecting regularities are needed in direct perception because the known facts are presented directly and immediately and not (as, in indirect perception) on the basis of some other facts. In direct perception all the justification (needed for knowledge) is right there in the experience itself.
 What, then, about the possibility of perceptual knowledge pure and direct, the possibility of coming to know, on the basis of sensory experience, that ‘a’ is ‘F’ where this does not require assumptions or knowledge that has a source outside the experience itself?  Where is this epistemological ‘pure gold’ to be found?
 There are, basically, two views about the nature of direct perceptual knowledge (coherentists would deny that any of our knowledge is basic in this sense). These views (following traditional nomenclature) can be called ‘direct realism’ and ‘representationalism’ or ‘representative realism’. A representationalist restricts direct perceptual knowledge to objects of a very special sort: Ideas, impressions, or sensations, sometimes called sense-data - entities in the mind of the observer. One directly perceives a fact, e.g., that ‘b’ is ‘G’, only when ‘b’ is a mental entity of some sort - a subjective appearance or sense-data - and ‘G’ is a property of this datum. Knowledge of these sensory states is supposed to be certain and infallible. These sensory facts are, so to speak, right up against the mind’s eye. One cannot be mistaken about these facts for these facts are, in reality, facts about the way things appear to be, and one cannot be mistaken about the way things appear to be. Normal perception of external conditions, then, turns out to be (always) a type of indirect perception. One ‘sees’ that there is a tomato in front of one by seeing that the appearance (of the tomato) has a certain quality (reddish and bulgy) and inferring as this is topically said to be automatic and unconscious, on the basis of certain background assumptions, e.g., that there typically is a tomato in front of one when one has experiences of this sort, that there is a tomato in front of one. All knowledge of objective reality, then, even what commonsense regards as the most direct perceptual knowledge, is based on an even more direct knowledge of the appearances.
 For the representationalist, then, perceptual knowledge of our physical surroundings is always theory-loaded and indirect. Such perception is ‘loaded’
 with the theory that there is some regular, some uniform, correlations between the way things appear (known in the perceptually direct way) and the way things actually are (known, if known at all, in a perceptual indirect way).
 The second view, direct realism, refuses to restrict perceptual knowledge, to an inner world of subjective experience. Though the direct realist is willing to concede that much of our knowledge of the physical world is indirect, however, direct and immediate it may sometimes feel, some perceptual knowledge of physical reality is direct. What makes it direct is that such knowledge is not based on, nor in any way dependent on, other knowledge and belief. The justification needed for the knowledge is right there in the experience itself.
 To understand the way this is supposed to work, consider an ordinary example, ‘S’ identifies a banana (learns that it is a banana) by noting its shape and colour - perhaps, even tasting and smelling it (to make sure it’s not wax). In this case the perceptual knowledge that is a banana is (the direct realist admits) indirect, dependence on S’s perceptual knowledge of its shape, colour, smell, and taste. ‘S’ learns that it is a banana by seeing that it is yellow, banana-shaped, etc. Nonetheless, S’s perception of the banana’s colour and shape is direct. ‘S’ does not see that the object is yellow, for example, by seeing, knowing, believing anything more basic - also not about the banana or anything else, e.g., his own sensations of the banana. ‘S’ has learned to identify such features, of course, but when ‘S’ learned to do is not an inference, even a unconscious inference, from other things be believed. What ‘S’ acquired was a cognitive skill, a disposition to believe of yellow objects he saw that they were yellow. The exercise of this skill does not require, and in no way depends on having of any other beliefs. S’s identificatorial successes will depend on his operating in certain special conditions, of course, ‘S’ will not, perhaps, be able to visually identify yellow objects in drastically reduced lighting, at funny viewing angles, or when afflicted with certain nervous disorders. But these facts about ‘S’ can see that something is yellow does not show that his perceptual knowledge (that ‘a’ is yellow) in any way deepens on a belief, let alone knowledge,  that he is in such special conditions. It merely shows that direct perceptual knowledge is the result of exercising a skill, an identificatorial skill, that like any skill. Requires certain conditions for its successful exercise. An expert basketball player cannot shoot accurately in a hurricane. He needs normal conditions to do what he has learned to do. So also, with individuals who have developed perceptual (cognitive) skills. They need normal conditions to do what they have learned to do. They need normal conditions to see, for example, that something is yellow. But they do not, any more than the basketball player, have to know they are in these conditions to do what being in these conditions enables them to do.
 This means, of course, that for a direct realist direct perceptual knowledge is fallible and corrigible. Whether ‘S’ sees that ‘a’ is ‘F’ depends on his being caused to believe that ’a’ is ‘F’ in conditions that are appropriate for an exercise of that cognitive skill. If conditions are right, then ‘S’ sees (hence, knows) that ‘a’ is ‘F’. If they aren’t, he doesn’t. Whether or not ‘S’ knows depends, then, not on what else, if anything, ‘S’ believes, but on the circumferences in which ‘S’ comes to believe. This being so, this type of direct realism is a form of externalism, direct perception of objective facts, pure perceptual knowledge of external events, is made possible because what is needed, by way of justification for such knowledge has been reduced. Background knowledge - and, in particular, the knowledge that the experience does, and suffices for knowing - is not needed.
 This mans that the foundations of knowledge are fallible. Nonetheless, though fallible, they are in no way derived. That is what makes them foundations. Even if they are brittle, as foundations sometimes are, everything else rests upon them
 The theory of representative realism holds that (1) there is a world whose existence and nature are independent of us and of our perceptual experience of it, and (2) perceiving an object located in that external world necessarily involves causally interacting with that object, (3) the information acquired in perceiving an object is indirect: It is information most immediately about the perceptual experience caused in us by the object, and only derivatively about the object itself:
  Clause 1. Makes representative realism a species of realism.
  Clause 2. Makes it a species of causal theory of perception.
  Clause 3. Makes it a species of representative as opposed
  to direct realism.
Traditionally, representative realism has been allied with an act/object analysis of sensory experience. Its act/object analysis is traditionally a major plank in arguments for representative realism. According to the act/object analysis of experience with content involves an object of experience to which the subject is related by an act of awareness (the event of experiencing that object). This is meant to apply not only to perceptions, which have material objects (whatever is perceived), but also to experiences like hallucinations and dream experiences, which do not. Such experiences nonetheless, appear to represent something. And their objects are supposed to be whatever it is that they represent. Act/object theorists may differ on the nature of objects of experience, which have been treated as properties, Meinongian objects (which may not exist or have any form of being), and, more commonly, private mental entities with sensory qualities. (The term ‘sense-data’ is now usually applied to the latter, but has also been used as a general term for objects of sense experiences, as in the work of G.E. Moore.) Act/object theorists may also differ on the relationship between objects of experience and objects of perception. In terms of representative realism, objects of perception (of which we are ‘indirectly aware’). Meinongians, however, may simply treat objects of perception as existing objects of experience.
 Realism in any area of thought is the doctrine that certain entities allegedly associated with that area are indeed real. Common sense realism - sometimes called ‘realism’, without t qualification - says that ordinary things like chairs and trees and people are real. Scientific realism says that theoretical posits like electrons and fields of force and quarks are equally real. And psychological realism says mental states like pain and beliefs are real. Realism can be upheld - and opposed - in all such areas, as it can with differently or more finely drawn provinces of discourse: For example, with discourse about colours, about the past, about possibility and necessity, or about matters of moral right and wrong. The realist in any such area insists on the reality of the entities in question in the discourse.
 If realism itself can be given a fairly quick characterization, it is more difficult to chart the various forms of opposition, for they are legion. Some opponents deny that there are any distinctive posits associated with the area of discourse under dispute: A good example is the emotivist doctrine that moral discourse does not posit values but serves only, like applause and exclamation, to express feelings. Other opponents deny that entity posited by the relevant discourse exist, or, at least, exist independently of our thinking about them: Here the standard example is ‘idealism’. And others again, insist that the entities associated with the discourse in question are tailored to our human capacities and interests and, to that extent, are as much a product of invention as a matter of discovery.
 Nevertheless, one us e of terms such as ‘looks’, ‘seems’, and ‘feels’ is to express opinion. ‘It looks as if the Labour Party will win the next election’ expresses an opinion about the party’s chances and does not describe a particular kind of perceptual experience. We can, however, use such terms to describe perceptual experience divorced from any opinion to which the experience may incline us. A straight-stick half in water looks bent, and does so to people completely familiar with this illusion who has, therefore, no inclination to hold that the stick is in fact bent. Such users of ‘looks’, ‘seems’, ‘taste’, etc. are commonly called ‘phenomenological’.
 The act/object theory holds that the sensory experience recorded by sentence employing sense is a matter of being directly acquainted with something which actually bears the red to me. I am acquainted with a red expanse (in my visual field): When something tastes bitter to me I am directly acquainted with a sensation with the property of being bitter, and so on and so forth. (If you do not understand the term ‘directly acquainted’, stick a pin into your finger. The relation you will then bear to your pain, as opposed to the relation of concern you might bear to another’s pain when told about it, is an instance e of direct acquaintance e in the intended sense.)
 The act/object account of sensory experience combines with various considerations traditionally grouped under the head of the argument for illusion to provide arguments for representative realism, or more precisely for the clause in it that contents that our senorily derived information about the world comes indirectly, that what we are most directly acquainted with is not an aspect of the world but an aspect for our mental sensory responses to it. Consider, for instance, the aforementioned refractive illusion, that of a straight stick in water looking bent. The act/object account holds that in this case we are directly acquainted with a bent shape. This shape, so the argument runs, cannot be the stick as it is straight, and thus, must be a mental item, commonly called a sense-datum. And, ion general sense-data-visual, tactual, etc. - is held to be the objects of direct acquaintance. Perhaps the most striking uses of the act/object analysis to bolster representative realism turns on what modern science tell us about the fundamental nature of the physical world. Modern science tells us that the objects of the physical world around us are literally made up of enormously many, widely separated, tiny particles whose nature can be given in terms of a small number of properties like mass, charge, spin and so on. (These properties are commonly called the primary qualities, as primary and secondary qualities represent a metaphysical distinction with which really belong to objects in the world and qualities which only appear to belong to them, or which human beings only believe to belong to them, because of the effects those objects produce ion human beings, typically through the sense organs, that is to say, something that does not hold everywhere by nature, but is producing in or contributed by human beings in their interaction with a world which really contains only atoms of certain kinds in a void. To think that some objects in the world are coloured, or sweet ort bitter is to attribute to objects qualities which on this view they do not actually possess. Rather, it is only that some of the qualities which are imputed to objects, e.g., colour, sweetness, bitterness, which are not possessed by those objects. But, of course, that is not how the objects look to us, not how they present to our senses. They look continuous and coloured. What then, can be these coloured expanses with which we are directly acquainted, be other than mentalistic thoughts of sense-data?
 Two objections dominate the literature on representative realism: One goes back to Berkeley (1685-1753) and is that representative realism lead straight to scepticism about the external world, the other is that the act/object account of sensory awareness is to be rejected in favour of an adverbial account.
 Traditional representative realism is a ‘veil of perception’ doctrine, in Bennetts (1971) phrase. Lock e’s idea (1632-1704) was that the physical world was revealed by science to be in essence colourless, odourless, tasteless and silent and that we perceive it by, to put it metaphorically, throwing a veil over it by means of our senses. It is the veil we see, in the strictest sense of ‘see’. This does not mean that we do not really see the objects around us. It means that we see an object in virtue of seeing the veil, the sense-data, causally related in the right way to that object, an obvious question to ask, therefore, is what justifies us in believing that there is anything behind the veil, and if we are somehow justified in believing that there is something behind the veil. How can we be confident of what it is like?
 One intuition that lies at the heart of the realist’s account of objectivity is that, in the last analysis, the objectivity of a belief is to be explained by appeal to the independent existence of the entities it concerns: Epistemological objectivity, this is, is to b e analysed in terms of ontological notions of objectivity. A judgement or beliefs are epistemological notions of objectivity, if and only if it stands in some specified reflation to an independently existing determinate reality. Frége (1848-1925), for example, believed that arithmetic could comprise objective knowledge only if the numbers it refers to, the propositions it consists of, the functions it employs, and the truth-values it aims at, are all mind-independent entities. And conversely, within a realist framework, to show that the members of a given class of judgements are merely subjective, it is sufficient to show that there exists no independent reality that those judgements characterize or refer to.
 Thus, it is favourably argued that if values are not part of the fabric of the world, then moral subjectivity is inescapable. For the realist, the, of epistemological notions of objectivity is to be elucidated by appeal to the existence of determinate facts, objects, properties, events and the like, which exit or obtain independent of any cognitive access we may have to them. And one of the strongest impulses towards platonic realism - the theoretical commitment to the existence of abstract objects like sets, numbers, and propositions - stems from the widespread belief that only if such things exist in their own right can we allow that logic, arithmetic and science are indeed objective. Though ‘Platonist’ realism in a sense accounts for mathematical knowledge, it postulates such a gulf between both the ontology and the epistemology of science and that of mathematics that realism is often said to make the applicability of mathematics in natural science into an inexplicable mystery
 This picture is rejected by anti-realists. The possibility that our beliefs and theories are objectively true is not, according to them, capable of being rendered intelligible by invoking the nature and existence of reality as it is in and of itself. If our conception of epistemological objective notions is minimal, requiring only ‘presumptive universality’, then alternative, non-realist analysers of it can seem possible - and even attractive. Such analyses have construed the objectivity of an arbitrary judgement as a function of its coherence with other judgements, of its possession of grounds that warrant it. Of its conformity to the a prior rules that constitute understanding, of its verifiability (or falsifiability), or if its permanent presence in the mind of God. On e intuitive common to a variety of different anti-realist theories is such that for our assertions to be objective, for our beliefs to comprise genuine knowledge, those assertions and beliefs must be, among other things, rational, justifiable, coherent, communicable and intelligible. But it is hard, the anti-realist claims, to see how such properties as these can be explained by appeal to entities as they are on and of themselves. On the contrary, according to most forms of anti-realism, it is only the basis of ontological subjective notions like ‘the way reality seems to us’, ‘the evidence that is available to us’, ‘the criteria we apply’, ‘the experience we undergo’ or ‘the concepts we have acquired’ that epistemological notions of objectivity of our beliefs can possibly be explained.
 The reason by which a belief is justified must be accessible in principle to the subject hold that belief, as Externalists deny this requirement, proposing that this makes knowing too difficult to achieve in most normal contexts. The internalist-Externalists debate is sometimes also viewed as a debate between those who think that knowledge can be naturalized (Externalists) and those who do not (internalist) naturalists hold that the evaluative notions used in epistemology can be explained in terms of non-evaluative concepts - for example, that justification can be explained in terms of something like reliability. They deny a special normative realm of language that is theoretically different from the kinds of concepts used in factual scientific discourse. Non-naturalists deny this and hold to the essential difference between normative and the factual: The former can never be derived from or constituted by the latter. So internalists tend to think of reason and rationality as non-explicable in natural, descriptive terms, whereas,  Externalists think such an explanation is possible.
 Although the reason, . . . to what we think to be the truth. The sceptic uses an argumentive strategy to show the alternatives strategies that we do not genuinely have knowledge and we should therefore suspend judgement. But, unlike the sceptics, many other philosophers maintain that more than one of the alternatives are acceptable and can constitute genuine knowledge. However, it seems dubitable to have invoked hypothetical sceptics in their work to explore the nature of knowledge. These philosophers did no doubt that we have knowledge, but thought that by testing knowledge as severely as one can, one gets clearer about what counts as knowledge and greater insight results.  Hence there are underlying differences in what counts as knowledge for the sceptic and other philosophical appearances. As traditional epistemology has been occupied with dissassociative kinds of debate that led to a dogmatism. Various types of beliefs were proposed as candidates for sceptic-proof knowledge, for example, those beliefs that are immediately derive by many as immune to doubt. Nevertheless, that they all had in common was that empirical knowledge began with the data of the senses, that this was safe from scepticism and that a further superstructure of knowledge was to be built on this firm basis.
 It might well be observed that this reply to scepticism fares better as a justification for believing in the existence of external objects, than as a justification of the views we have about their nature. It is incredible that nothing independent of us is responsible for the manifest patterns displayed by our sense-data, but granting this leaves open many possibilities about the nature of the hypnotized external reality. Direct realists often make much of the apparent advantage that their view has in the question of the nature of the external world. The fact of the matter is, though, that it is much harder to arrive at tenable views about the nature of external reality than it is to defend the view that there is an external reality of some kind or other. The history of human thought about the nature of the external world is littered with what are now seen (with the benefit of hindsight) to be egregious errors - the four element theory, phlogiston, the crystal spheres, vitalism, and so on. It can hardly be an objection to a theory that makes the question of the nature of external reality much harder than the question of its existence.
 The way we talk about sensory experience certainly suggests an act/object view. When something looks thus and so in the phenomenological sense, we naturally describe the nature of our sensory experience by saying that we are acquainted with a thus and so ‘given’. But suppose that this is a misleading grammatical appearance, engendered by the linguistic propriety of forming complete, putatively referring expressions like ‘the bent shape on my visual field’, and that there is no more a bent shape in existence for the representative realist to contend to be a mental sense-data, than there is a bad limp in existence when someone has, as we say, a bad limp. When someone has a bad limo, they limp badly, similarly, according to an adverbial theorist, when, as we naturally put it, I am aware of a bent shape, we would better express the way things are by saying that I sense bent shape-ly. When the act/object theorist analyses as a feature of the object which gives the nature of the sensory experience, the adverbial theorist analyses as a mode of sense which gives the nature of the sensory experience. (The decision between the act/object and adverbial theories is a hard one.)
 In the best-known form the adverbial theory of experience proposes that the grammatical object of a statement attributing an experience to someone be analysed as an adverb. For example,
(1) Rod is experiencing a pink square
is rewritten as? ,
Rod is experiencing (pink square)-ly
This is presented as an alterative to the act/object analysis, according to which the truth of a statement like (1) requires the existence of an object of experience corresponding to its grammatical object. A commitment to the explicit adverbialization of statements of experience is not, however, essential to adverbialism. The core of the theory consisted, rather, in the denial of objects of experience, as opposed to objects of perception, and coupled with the view that the role of the grammatical object is a statement of experience is to characterize more fully the sort of experience which is being attributed to the subject. The claim, then, is that the grammatical object is functioning as a modifier, and, in particular, as a modifier of a verb. If this is so, it is perhaps appropriate to regard it as a special kind of adverb at the semantic level.
 Nonetheless, in the arranging accordance to the act/object analysis of experience, every experience with content involves an object of experience to which the subject is related by an act of awareness in the event of experiencing that object. Such as these experiences are, it is, nonetheless. The experiences are supposed to be whatever it is that they represent. Act, an object theorist may differ on the nature of objects of experience, which h have been treated as properties. However, and, more commonly, private mental objects in which may not exist have any form of being, and, with sensory qualifies the experiencing imagination may walk upon the corpses of times’ generations, but this has also been used as a unique application to is mosaic structure in its terms for objects of sensory experience or the equivalence of the imaginations striving from the mental act as presented by the object and forwarded by and through the imaginistic thoughts that are released of a vexing imagination. Finally, in the terms of representative realism, objects of perception of which we are ‘directly aware’, as the plexuity in the abstract objects of perception exist if objects of experience.
 As the aforementioned, traditionally representative realism is allied with the act/object theory. But we can approach the debate or by rhetorical discourse as meant within dialectic awareness, for which representative realism and direct realism  are achieved by the mental act in abdication to some notion of regard or perhaps, happiness, all of which the prompted excitations of the notion expels or extractions of information processing. Mackie (1976( argues that Locke (1632-1704) can be read as approaching the debate ion television. My senses, in particular my eyes and ears, ‘tell’ me that Carlton is winning. What makes this possible is the existence of a long and complex causal chain of electro-magnetic radiation from the game through the television cameras, various cables between my eyes and the television screen. Each stage of this process carries information about preceding stages in the sense that the way things are at a given stage depends on, and the way things are at preceding stages. Otherwise, the information would not be transferred from the game to my brain. There needs to be a systematic covariance between the state of my brain and the state unless it obtains between intermediate members of the long causal chain. For instance, if the state of my retina did not systematically remit or consign with the state of the television screen before me, my optic nerve would have, so to speak, nothing to go on to tell my brain about the screen, and so in turn would have nothing to go on to tell my brain about the game. There is no information at a distance’.
 A few of the stages in this transmission of information between game and brain are perceptually aware of them. Much of what happens between brain and match I am quite ignorant about, some of what happens I know about from books, but some of what happens I am perceptually aware of the images on the scree. I am also perceptually aware of the game. Otherwise, I could not be said to watch the game on television. Now my perceptual awareness of the match depends on my perceptual awareness of the screen. The former goes by means of the latter. In saying this I am not saying that I go through some sort of internal monologue like ‘Such and such images on the screen are moving thus and thus. Therefore, Carlton is attacking the goal’. Indeed, if you suddenly covered the screen with a cloth and asked me (1) to report on the images, and (2) to report in the game. I might well find it easier to report on the game than on the images. But that does not mean that my awareness of the game does not go by way of my awareness of the images on the screen. The shows that I am more interested in the game than in the screen, and so am storing beliefs about it in preference e to beliefs about the screen.
 We can now see how elucidated representative realism independently of the debate between act/object and adverbial theorists about sensory experience. Our initial statement of representative realism talked of the information acquired in perceiving an object being most immediately about the perceptual experience caused in us by the object, and only derivatively about objects itself, in the act/object, sense-data approach, what is held to make that true is that the fact that what we are immediately aware of it’s mental sense-datum. But instead, representative realists can put their view this way: Just as awareness of the match game by means of awareness of the screen, so awareness of the screen foes by way of awareness of experience., and in general when subjects perceive objects, their perceptual awareness always does by means of the awareness of experience.
 Why believe such a view? Because of the point that was inferred earlier: The worldly provision by our senses is so very different from any picture provided by modern science. It is so different in fact that it is hard to grasp what might be meant by insisting that we are in epistemologically direct contact with the world.
 An argument from illusion is usually intended to establish that certain familia r facts about illusion disprove the theory of perception and called naïve or direct realism. There are, however, many different versions of the argument which must be distinguished carefully. Some of these premisses (the nature of the appeal to illusion): Others centre on the interpretation of the conclusion (the kind of direct realism under attack). In distinguishing important differences in the versions of direct realism. One might be taken to be vulnerable to familiar facts about the possibility of perceptual illusion.
 A crude statement of direct realism would concede to the connection with perception, such that we sometimes directly perceive physical objects and their properties: We do not always perceive physical objects by perceiving something else, e.g., a sense-data. There are, however, difficulties with this formulation of the view. For one thing a great many philosophers who are not direct realists would admit that it is a mistake to describe people as actually perceiving something other than a physical object. In particular, such philosophers might admit, we should never say that we perceive sense-data. To talk that way would be to suppose that we should model our understanding of our relationship to sense-data on our understanding of the ordinary use of perceptual verbs as they describe our relation to the physical world, and that is the last thing paradigm sense-data theorists had better want. At least, many of the philosophers who objected to direct realism would prefer to express what they were objecting too in terms of a technical and philosophical controversial concept such as acquaintance. Using such a notion, we could define direct realism this way: In veridical experience we are directly acquainted with parts, e.g., surfaces, or constituents of physical objects. A less cautious version of the view might drop the reference to veridical experience and claim simply that in all parts or constituents of physical objects.
 We know things by experiencing them, and knowledge of acquaintance. (Russell changed the preposition to ’by’) is epistemically prior to and has a relatively higher degree of epistemic justification than knowledge about things. Indeed, sensation has ‘the one great value of trueness or freedom from mistake’.
 A thought (using that term broadly, to mean any mental state) constituting knowledge of acquaintance with thing is more or less causally proximate to sensations caused by that thing is more or less distant causal y, being separated from the thing and experience of it by processes of attention and inference. At the limit, if a thought is maximally of the acquaintance type, it is the first mental state occurring in a object to which the thought refers, i.e., it is a sensation. The things we have knowledge of acquaintance e include ordinary objects in the external world, such as the Sun.
 Grote contrasted the imaginistic thoughts involved in knowledge of acquaintance with things, with the judgements involved in knowledge about things, suggesting that the latter but not the former are contentful mental states. Elsewhere, however, he suggested that every thought capable of constituting knowledge of or about a thing involves a form, idea, or what we might call conceptual propositional content, referring the thought to its object. Whether contentful or not, thoughts constituting knowledge of acquaintance with a thing as r relatively indistinct, although this indistinctness does not imply incommunicability. Yet, thoughts constituting knowledge about a thing are relatively distinct, as a result of ‘the application of notice or attention’ to the ‘confusion or chaos’ of sensation. Grote did not have an explicit theory of reference e, the relation by which a thought of or about a specific thing. Nor did he explain how thoughts can be more or less indistinct.
 Helmholtz (1821-94) held unequivocally that all thoughts capable of constituting knowledge, whether ‘knowledge e which has to do with notions’ or ‘mere familiarity with phenomena’ are judgements or, we may say, have conceptual propositional contents. Where Grote saw a difference e between distinct and indistinct thoughts. Helmholtz found a difference between precise judgements which are expressible in words and equally precise judgement which, in principle, are not expressible in words, and so are not communicable.
 James (1842-1910), however, made a genuine advance over Grote and Helmholtz by analysing the reference relations holding between a thought and the specific thing of or about which it is knowledge. In fact, he gave two different analyses. On both analyses, a thought constituting knowledge about a thing refers to and is knowledge about ‘a reality, whenever it actually or potentially terminates in’ a thought constituting knowledge of acquaintance with that thing. The two analyses differ in their treatments of knowledge of acquaintance. On James’s first analyses, reference in both sorts of knowledge is mediated by causal chains. A thought constituting pure knowledge of acquaintance with a thing refers to and is knowledge of ‘whatever reality it directly or indirectly operates on and resembles’. The concepts of a thought ‘operating in’ a thing or ‘terminating in’ another thought are causal, but where Grote found chains of efficient causation connecting thought and referent. James found teleology and final causes. On James’s later analysis, the reference involved in knowledge of acquainting e with a thing is direct. A thought constituting knowledge of acquaintance with a thing as a constituent and the thing and the experience of it are identical.
 James further agreed with Grote that pure knowledge of acquaintance with things, eg., sensory experience, is epistemically prior to knowledge about things. While the epistemic justification involved in knowledge about all thoughts about things are fallible and their justification is augmented by their mutual coherence. James was unclear about the precise epistemic status of knowledge of acquaintance. At times, thoughts constituting pure knowledge of acquaintance are said to posses ‘absolute veritableness’ and ‘the maximal conceivable truth’, suggesting that such thoughts are genuinely cognitive and that they provide an infallible epistemic foundation. At other times, such thoughts are said not to bear truth-values, suggesting that ‘knowledge’ of acquaintance is not genuine knowledge at all, but only a non-cognitive necessary condition of genuine knowledge, that is to say, the knowledge about things.
 What is more that, Russell (1872-1970) agreed with James that knowledge of things by acquaintance ‘is essentially simpler than any knowledge of truths, and logically independent of knowledge of truth?’. That the mental states involved when one is acquainted with things do not have propositional contents. Russell’s reasons were  to seem as having been similar to James’s. Conceptually unmediated reference to particulars is necessary for understanding any proposition mentioning a particular and, if scepticism about the external world is to be avoided, some particulars must be directly perceived. Russell vacillated about whether or not the absence of propositional content renders knowledge by acquaintance incommunicable.
 Russell agreed with James that different accounts should be given of reference as it occurs in knowledge by acquaintance and in knowledge about things, and that in the former case reference is direct. But, Russell objected on the number of grounds to James’s causal account of the indirect reference involved in knowledge about things. Russell gave a descriptional rather than a causal analysis of that sort of reference. A thought is about a thing when the content of the thought involves a definite description uniquely satisfied by the thing referred to. Yet, he preferred to speak of knowledge of things by description, than of knowledge about things.
 Russell advanced beyond Grote and James by explaining how thoughts can be more or less articulate and explicit. If one is acquainted with a complex thing without being aware of or acquainted with its complexity, the knowledge one has by acquaintance e with that thing is vague and inexplicit. Reflection and analysis can lead to distinguish constituent parts of the object of acquaintance and to obtain progressively more distinct, explicit, and complete knowledge about it.
 Because one can interpret the reflation of acquaintance or awareness as one that is not epistemic, i.e., not a kind of propositional knowledge, it is important to distinguish the views read as ontological theses from a view one might call epistemological direct realism: In perception we are, on, at least some occasions, non-inferentially justified in believing a proposition asserting the existence e of a physical object. A view about what the object of perceptions are. Direct realism is a type of realism, since it is assumed that these objects exist independently of any mind that might perceive them: And so it thereby rules out all forms of idealism and phenomenalism, which holds that there are no such independently existing objects. Its being a ‘direct realism rules out those views’ defended under the rubic of ‘critical realism’, of ‘representative realism’, in which there is some non-physical intermediary - usually called a ‘sense-data’ or a ‘sense impression’ - that must first be perceived or experienced in order to perceive the object that exists independently of this perception. According to critical realists, such an intermediary need not be perceived ‘first’ in a temporal sense, but it is a necessary ingredient which suggests to the perceiver an external reality, or which offers the occasion on which to infer the existence of such a reality. Direct realism, however, denies the need for any recourse to mental go-between in order to explain our perception of the physical world.
 This reply on the part of the direct realist does not, of course, serve to refute the global sceptic, who claims that, since our perceptual experience could be just as it is without there being any real properties at all, we have no knowledge of any such properties. But no view of perception alone is sufficient to refute such global scepticism. For such a refutation we must go beyond a theory that claims how best to explain our perception of physical objects, and defend a theory that best explains how we obtain knowledge of the world.
 All is the equivalent for an external world, as philosophers have used the term, is not some distant planet external to Earth. Nor is the external world, strictly speaking, a world. Rather, the external world consists of all those objects and events which exist external to perceiver. So the table across the room is part of the external world, and so is the room in part of the external world, and so is its brown colour and roughly rectangular shape. Similarly, if the table falls apart when a heavy object is placed on it, the event of its disintegration is a pat of the external world.
 One object external to and distinct from any given perceiver is any other perceiver. So, relative to one perceiver, every other perceiver is a part of the external world. However, another way of understanding the external world results if we think of the objects and events external to and distinct from every perceiver. So conceived the set of all perceivers makes up a vast community, with all of the objects and events external to that community making up the external world. Thus, our primary considerations are in the concern from which we will suppose that perceiver are entities which occupy physical space, if only because they are partly composed of items which take up physical space.
 What, then, is the problem of the external world. Certainly it is not whether there is an external world, this, and much is taken for granted. Instead, the problem is an epistemological one which, in rough approximation, can be formulated by asking whether and if so how a person gains of the external world. So understood, the problem seems to admit of an easy solution. Thee is knowledge of the external world which persons acquire primarily by perceiving objects and events which make up the external world.
 However, many philosophers have found this easy solution problematic. Nonetheless, the very statement of ‘the problem of the external world itself’ will be altered once we consider the main thesis against the easy solution.
 One way in which the easy solution has been further articulated is in terms of epistemological direct realism. This theory is the realist insofar as it claims that objects and events in the external world, along with many of their various features, exist independently of and are generally unaffected by perceivers and acts of perception in which they engage. And this theory is epistemologically direct since it also claims that in perception people often, and typically acquire immediate non-inferential knowledge of objects and events in the external world. It is on this latter point that it is thought to face serious problems.
 The main reason for this is that knowledge of objects in the external world seems to be dependent on some other knowledge, and so would not qualify as immediate and non-inferentially is claimed that I do not gain immediate non-inferential perceptual knowledge that thee is a brown and rectangular table before me, because I would know such a proposition unless I knew that something then appeared brown and rectangular. Hence, knowledge of the table is dependent upon knowledge of how it appears. Alternately expressed, if there is knowledge of the table at all, it is indirect knowledge, secured only if the proposition about the table may be inferred from propositions about appearances. If so, epistemological direct realism is false’
 This argument suggests a new way of formulating the problem of the external world:
  :Problem of the external world: Can firstly, have?
  knowledge of propositions about objects and events
  in the external world based on or upon propositions
  which describe how the external world appears,
  i.e., upon appearances?
Unlike our original formulation of the problem of the external world, this formulation does not admit of an easy solution. Instead, it has seemed to many philosophers that it admits of no solution at all, so that scepticism regarding the eternal world is only remaining alternative.
 This theory is realist in just the way described earlier, but it adds, secondly, that objects and events in the external world are typically directly perceived, as are many of their features such as their colour, shapes, and textures.
 Often perceptual direct realism is developed further by simply adding epistemological direct realism to it. Such an addition is supported by claiming that direct perception of objects in the external world provides us with immediate non-referential knowledge of such objects. Seen in this way, perceptual direct realism is supposed to support epistemological direct realism, strictly speaking they are independent doctrines. One might consistently, perhaps even plausibly, hold one without also accepting the other.
 Direct perception is that perception which is not dependent on some other perception. The main opposition to the claim that we directly perceive external objects comes from direct or representative realism. That theory holds that whenever an object in the external world is perceived, some other object is also perceived, namely a sensum - a phenomenal entity of some sort. Further, one would not perceive the external object if one would not perceive the external object if one were to fail to receive the sensum. In this sense the sensum is a perceived intermediary, and the perception of the external object is dependent on the perception of the sensum. For such a theory, perception of the sensum is direct, since it is not dependent on some other perception, while perception on the external object is indirect. More generally, for the indirect t realism., all directly perceived entities are sensum. On the other hand, those who accept perceptual direct realism claim that perception of objects in the external world is typically direct, since that perception is not dependent on some perceived intermediaries such as sensum.
 It has often been supposed, however, that the argument from illusion suffices to refute all forms of perceptual direct realism. The argument from illusion is actually a family of different arguments rather than one argument. Perhaps the most familiar argument in this family begins by noting that objects appear differently to different observers, and even to the same observers on different occasions or in different circumstances. For example, a round dish may appear round to a person viewing it from directly above and elliptical to another viewing it from one side. As one changes position the dish will appear to have still different shapes, more and more elliptical in some cases, closer and closer to round in others. In each such case, it is argued, the observer directly sees an entity with that apparent shape. Thus, when the dish appears elliptical, the observer is said to see directly something which is elliptical. Certainly this elliptical entity is not the top surface of the dish, since that is round. This elliptical entity, a sensum, is thought to be wholly distinct from the dish.
 In seeing the dish from straight above it appears round and it might be thought that then directly sees the dish rather than a sensum. But here too, it relatively sett in: The dish will appear different in size as one is placed at different distances from the dish. So even if in all of these cases the dish appears round, it will; also, appear to have many different diameters. Hence, in these cases as well, the observer is said to directly see some sensum, and not the dish.
 This argument concerning the dish can be generalized in two ways. First, more or less the same argument can be mounted for all other cases of seeing and across the full range of sensible qualities - textures and colours in addition to shapes and sizes. Second, one can utilize related relativity arguments for other sense modalities. With the argument thus completed, one will have reached the conclusion that all cases of non-hallucinatory perception, the observer directly perceives a sensum, and not an external physical object. Presumably in cases of hallucination a related result holds, so that one reaches the fully general result that in all cases of perceptual experience, what is directly perceived is a sensum or group of sensa, and not an external physical object, perceptual direct realism, therefore, is deemed false.
 Yet, even if perceptual direct realism is refuted, this by itself does not generate a problem of the external world. We need to add that if no person ever directly perceives an external physical object, then no person ever gains immediate non-inferential knowledge of such objects. Armed with this additional premise, we can conclude that if there is knowledge of external objects, it is indirect and based upon immediate knowledge of sensa. We can then formulate the problem of the external world in another way:
  Problems of the external world: can, secondly? ,
  have knowledge of propositions about objects and
  events in the external world based upon propositions
  about directly perceived sensa?
It is worth nothing the differences between the problems of the external world as expounded upon its first premise and the secondly proposing comments as listed of the problems of the external world, we may, perhaps, that we have knowledge of the external world only if propositions about objects and events in the external world that are inferrable from propositions about appearances.
 Some philosophers have thought that if analytical phenomenalism were true, the situational causalities would be different. Analytic phenomenalism is the doctrine that every proposition about objects and events in the external world is fully analysable into, and thus is equivalent in meaning to, a group of inferrable propositions. The numbers of inferrable propositions making up the analysis in any single propositioned object and/or event in the external world would likely be enormous, perhaps, indefinitely many. Nevertheless, analytic phenomenalism might be of help in solving the perceptual direct realism of which the required deductions propositioned about objects and events in the external world from those that are inferrable from prepositions about appearances. For, given analytical phenomenalism there are indefinite many in the inferrable propositions about appearances in the analysis of each proposition taken about objects and events in the external world is apt to be inductive, even granting the truth of a analytical phenomenalism. Moreover, most of the inferrable propositions about appearances into which we might hope to analyse of the external world, then we have knowledge of the external world only if propositions about objects and events in the external world would be complex subjunctive conditionals such as that expressed by ‘If I were to seem to see something red, round and spherical, and if I were to seem to try to taste what I seem to see, then most likely I would seem to taste something sweet and slightly tart’. But propositionally inferrable appearances of this complex sort will not typically be immediately known. And thus knowledge of propositional objects and event of the external world will not generally be based on or upon immediate knowledge of such propositionally making appearances.
 Consider upon the appearances expressed by ‘I seem to see something red, round, and spherical’ and ‘I seem to taste something sweet and slightly tart’. To infer cogently from these propositions to that expressed by ‘There is an apple before me’ we need additional information, such as that expressed by ‘Apples generally cause visual appearance of redness, roundness, and spherical shape and gustatory appearance of sweetness and tartness’. With this additional information., the inference is a good on e, and it is likely to be true that there is an apple there relative to those premiered. The cogency of the inference, however, depends squarely on the additional premise, relative only to the stated inferrability placed upon appearances, it is not highly probable that thee is an apple there.
 Moreover, there is good reason to think that analytic phenomenalism is false. For each proposed translation of an object and eventfully external world into the inferrable propositions about appearances. Mainly enumerative induction is of no help in this regard, for that is an inference from premisses about observed objects in a certain set-class having some properties ‘F’ and ‘G’ to unobserved objects in the same set-class having properties ‘F’ and ‘G’, to unobserved objects in the same set-class properties ‘F’ and ‘G’. If satisfactory, then we have knowledge of the external world if propositions are inferrable from propositions about appearances, however, concerned considerations drawn upon appearances while objects and events of the external world concern for externalities of objects and interactive categories in events, are. So, the most likely inductive inference to consider is a causal one: We infer from certain effects, described by promotional appearances to their likely causes, described by external objects and event that profited emanation in the concerning propositional state in that they occur. But, here, too, the inference is apt to prove problematic. But in evaluating the claim that inference constitutes a legitimate and independent argument from, one must explore the question of whether it is a contingent fact that, at least, most phenomena have explanations and that be so, that a given criterion, simplicity, were usually the correct explanation, it is difficult to avoid the conclusion that if this is true it would be an empirical fact about our selves in discovery of an reference to the best explanation.
 Defenders of direct realism have sometimes appealed to an inference to the best explanation to justify prepositions about objects and events in the external world, we might say that the best explanation of the appearances is that they are caused by external objects. However, even if this is true, as no doubt it is, it is unclear how establishing this general hypophysis helps justify specific ordination upon the proposition about objects and event in the external world, such as that these particular appearances of a proposition whose inferrable properties about appearances caused by the red apple.
 The point here is a general one: Cogent inductive inference from the inferrable proposition about appearances to propositions about objects and events in the external world are available only with some added premiss expressing the requisite causal relation, or perhaps some other premiss describing some other sort of correlation between appearances and external objects. So there is no reason to think that indirect knowledge secured if the prepositions about its outstanding objectivity from realistic appearances, if so, epistemological direct realism must be denied. And since deductive and inductive inferences from appearance to objects and events in the external world are propositions which seem to exhaust the options, no solution to its argument that sustains us of having knowledge of propositions about objects and events in the external world based on or upon propositions which describe the external world as it appears at which point that is at hand. So unless there is some solution to this, it would appear that scepticism concerning knowledge  of the external world would be the most reasonable position to take
 If the argument leading to some additional premise as might conclude that if there is knowledge of external objects if is directly and based on or upon the immediate knowledge of sensa, such that having knowledge of propositions about objects and events in the external world based on or upon propositions about directly perceived sensa? Broadly speaking, there are two alternatives to both the perceptual indirect realism, and, of course, perceptual phenomenalism. In contrast to indirect t realism, and perceptual phenomenalism is that perceptual phenomenalism rejects realism outright and holds instead that (1) physical objects are collections of sensa, (2) in all cases of perception, at least one sensa is directly perceived, and, (3) to perceive a physical object one directly perceives some of the sensa which are constituents of the collection making up that object.
 Proponents of each of these position try to solve the conditions not engendered to the species of additional persons ever of directly perceiving an external physical object, then no person ever gains immediate non-referential knowledge of such objects in different ways, in fact, if any the better able to solve this additional premise, that we would conclude that if there is knowledge of external objects than related doctrines for which time are aforementioned. The answer has seemed to most philosophers to be ‘no’, for in general indirect realists and phenomenalists have strategies we have already considered and rejected.
 In thinking about the possibilities of such that we need to bear in mind that the term for propositions which describe presently directly perceived sensa. Indirect realism typically claim that the inference from its presently directly perceived sensa to an inductive one, specifically a causal inference from effects of causes. Inference of such a sort will perfectly cogent provides we can use a premiss which specifies that physical objects of a certain type are causally correlated with sensa of the sort currently directly perceived. Such a premiss will itself be justified, if at all, solely on the basis of propositions described presently directly perceived sensa. Certainly for the indirect realist one never directly perceives the causes of sensa. So, if one knows that, say, apples topically cause such-and-such visual sensa, one knows this only indirectly on the basis of knowledge of sensa. But no group of propositionally perceived sensa by itself supports any inferences to causal correlations of this sort. Consequently, indirect realists are in no p position to solve such categorically added premises for which knowledge is armed with additional premise, as containing of external objects, it is indirect and based on or upon immediate knowledge of sensa. The consequent solution of these that are by showing that propositions would be inductive and causal inference from effects of causes and show inductively how derivable for propositions which describe presently perceived sensa.
 Phenomenalists have often supported their position, in part, by noting the difficulties facing indirect t realism, but phenomenalism is no better off with respect to inferrable prepositions about objects and events responsible for unspecific appearances. Phenomenalism construe physical objects as collections of sensa. So, to infer an inference from effects to causes is to infer a proposition about a collection from propositions about constituent members of the collective one, although not a causal one. Nonetheless, namely the inference in question will require a premise that such-and-such directly perceived sensa are constituents of some collection ‘C’, where ‘C’ is some physical object such as an apple. The problem comes with trying to justify such a premise. To do this, one will need some plausible account of what is mean t by claiming that physical objects are collections of sensa. To explicate this idea, however, phenomenalists have typically turned to analytical phenomenalism: Physical objects are collections of sensa in the sense that propositions about physical objects are analysable into propositions about sensa. And analytical phenomenalism we have seen, has been discredited.
 If neither propositions about appearances nor propositions accorded of the external world can be easily solved, then scepticism about external world is a doctrine we would be forced to adopt. One might even say that it is here that we locate the real problem of the external world. ‘How can we avoid being forced into accepting scepticism’?
 In avoiding scepticism, is to question the arguments which lead to both propositional inferences about the external world an appearances. The crucial question is whether any part of the argument from illusion really forces us to abandon the incorporate perceptual direct realism. To help see that the answer is ‘no’ we may note that a key premise in the relativity argument links how something appears with direct perception: The fact that the dish appears elliptical is supposed to entail that one directly perceives something which is elliptical. But is there an entailment present? Certainly we do not think that the proposition expressed by ‘The book appears worn and dusty and more than two hundred years old’ entails that the observer directly perceives something which is worn and dusty and more than two hundred years old. And there are countless other examples like this one, where we will resist the inference from a property ‘F’ appearing to someone to claim that ‘F’ is instantiated in some entity.
 Proponents of the argument from illusion might complain that the inference they favour works only for certain adjectives, specifically for adjectives referring to non-relational sensible qualities such as colour, taste, shape, and the like. Such a move, however, requires an arrangement which shows why the inference works in these restricted cases and fails in all others. No such argument has ever been provided, and it is difficult to see what it might be.
 If the argument from illusion is defused, the major threat facing a knowledge of objects and or events in the external world primarily by perceiving them. Also, its theory is realist in addition that objects and events in the external world are typically directly perceived as are many of their characteristic features. Hence, there will no longer be any real motivation for it would appear that scepticism concerning knowledge of the external world would be the most reasonable position to take. Of course, even if perceptual directly realism is reinstated, this does not solve, by any means, the main reason for which that knowledge of objects in the external world seem to be dependent on some other knowledge, and so would not qualify as immediate and non-reference, along with many of their various features, exist independently of and are generally unaffected by perceivers and acts of perception in which they engage. That problem might arise even for one who accepts perceptual direct realism. But, there is reason to be suspicious in keeping with the argument that one would not know that one is seeing something blue if one failed to know that something looked blue. In this sense, there is a dependance of the former on the latter, what is not clear is whether the dependence is epistemic or semantic. It is the latter if, in order to understand what it is to see something blue, one must also understand what it is fort something to look blue. This may be true, even when the belief that one is seeing something blue is not epistemically dependent on or based upon the belief that something looks blue. Merely claiming, that there is a dependent relation does not discriminate between epistemic and semantic dependence. Moreover, there is reason to think it is not an epistemic dependence. For in general, observers rarely have beliefs about how objects appar, but this fact doe not impugn their knowledge that they are seeing, e.g., blue objects.
 Along with ‘consciousness’, experience is the central focus of the philosophy of mind. Experience is easily thought of as a stream of private events, known only to their possessor, and baring at best problematic relationship to any other events, such as happening in an external world or similar stream of either possessors. The stream makes up the conscious life of the possessor. The stream makes up the conscious life of the possessor. With this picture there is a complete separation of mind and world, and in spite of great philosophical effort the gap, once opened, proves impossible to bridge both ‘idealism’ and ‘scepticism’ are common outcomes. The aim of much recent philosophy, therefore, is to articulate a less problematic conception of experience, making it objectively accessible, so that the facts about how a subject experiences the world are in principle as knowable as the facts about how the same subject digests food. A beginning on this task may be made by observing that experience have contents: ‘Content’ has become a technical term in philosophy for whatever it is a representation has that makes it semantically evaluable. Thus, a statement is something said to have a proposition or truth condition as its content: A term is sometimes said to have a concept as its content. Much less is known about how to characterize the contents of non-linguistic representations than is known about characterizing linguistic representations. ‘Content’ is a useful term precisely because it allows one to abstract away from questions about what semantic properties representations have, a representation’s content is just whatever it is that underwrites its semantic evaluation.
 A great deal of philosophical effort has been lavished on the attempt to naturalize content, e.g., to explain in non-semantic, non-intentional terms what it is for something to be representation (have ‘content’), and what it is for something to give some particular content than some other. There appear to be only our types of theory that have been proposed: Theories that ground representation in (1) similarity, (2) covariance (3) functional role, and (teleology.
 Similarity theories hold that ‘r’ represents ‘χ’ in virtue of being similar to ‘χ’. This has seemed hopeless to most as a theory of mental representation because it appears to require that things in the brain must share properties with the thingos they represent: To represent a cat as furry appears to require something furry in the brain. Perhaps, a notion of similarity that is naturalized and does not involve property sharing can be worked out, but it is not obvious how.
 Covariance theories hold that r’s representing ‘χ’ is grounded in the fact that r’s occurrence covaries with that of ‘χ’. This is most compelling when one thinks about detection systems: The firing of neural structure in the visual system is said to represent vertical orientations if its firing covaries with the occurrence of vertical lines in the visual field. Dretske (1981) and Fodor (1987) have, in different ways, attempted to promote this idea into a general theory of content.
 Teleological theories hold that ‘r’ represents ‘χ’ if it is r’s function to indicate (i.e., covary with) ‘χ’. Teleological theories differ depending on the theory of functions they import. Perhaps, the most important distinction is that between historical theories and functions, as historical theories individuate functional states, hence content, in a way that is sensitive to the historical development of the state, i.e., to factors such as the way the state was ‘learned’, or the way it evolved. An historical theory might hold that the function of ‘r’ is to indicate ‘χ’ only if the capacity to token ‘r’ was developed (selected, learned) because it indicates ‘χ’. Thus, a state physically indistinguishable from ‘r’ (physical stares being a-historical) but lacking r’s historical origins would not represent ‘χ’ according to historical theories.
 Theories of representational content may be classified according to whether they are atomistic or holistic and according to whether they are externalistic or internalistic.  Primarily, the alternative was for something expressed or implied by the intendment for integrating the different use of the terms ‘internalism’ and ‘externalisms’ has to do with the issue of how the content of beliefs and thoughts is determined: According to an internalist view of content, the content of such intentional states depend’s only on the non-relational, internal properties of the individual’s mind or brain, and not at all on his physical and social environment. While according to an externalist view, content is significantly affected by such external factors.
 As with justification and knowledge, the traditional view of content has been strongly internalist in character. The main argument for externalisms derives from the philosophy of language, more specifically from the various phenomena pertaining to natural kind terms, indexical, etc., that motivate the views that have come to be known as ‘direct reference’ theories. Such phenomena seem, at least, to show that the belief of thought content that can be properly attributed to a person is dependent on facts about his environment -, e.g., whether he is on Earth or Twin Earth, what in fact he is pointing at, the classificatorial criteria employed by the experts in his social group etc. - not just on what is going on internally in his mind or brain.
 An objection to externalist accounts of content is that to know the contents of our beliefs or thoughts ‘from the inside’, simply by reflection. If content is dependent on external factors, then knowledge of content should depend on knowledge of these factors - which will not in general be available to the person whose belief or thought is in question.
 The adoption of an externalist account of mental content would seem to support an externalist way: If part or all of the justification in which if only part of the content of a belief is inaccessible to the believer, then both the justifying status of other beliefs in relation to that content and the status of the content as justifying further beliefs will be similarly inaccessible, thus contravening the internalist requirement for justification. An internalist must insist that there are no justification relations of these sorts, that only internally accessible content can either be justified or justly anything else, but such a response appears lame unless it is coupled with an attempt to show that the externalist account of content is mistaken.
 Atomistic theories take a representation’s content to be something that representation’s relation to other representations. What Fodor (1987) calls the crude causal theory, for example, takes a representation to be a |cow| - a mental representation with the same content as the word ‘cow’ - if its tokens are caused by instantiations of the property of being-a-cow, and this is a condition that places no explicit constraints on how |cow|’s must or might relate to other representations. Holistic theories contrast with atomistic theories in taking the relations a representation bears to others to be essential to its content. According to functional role theories, a representation is a |cow| if it behaves like a |cow| behave in inference.
 Internalist theories take the content of a representation to be a matter determined by factors internal to the system that uses it. Thus, what Block (1986) calls ‘short-armed’ functional role theories are internalist. Externalist theories take the content of a representation to be determined, in part at least, by factors external to the system that uses it. Covariance theories, as well as teleological theories that invoker an historical theory of functions, take content to be determined by ‘external’ factors. Externalist theories (sometimes called non-individualistic theories, following Burge, 1979) have the consequence that molecule for molecule identical cognitive systems might yet harbor representations with different contents. This has given rise to a controversy concerning ‘narrow’ content. If we assume some form of externalist theory is correct, then contents is, in the first instance ‘wide’ content, i.e., determined in part by factors external to the representing system. On the other hand, it seems clear that, on plausible assumptions about how to individuate psychological capacities, internally equivalent systems must have the same psychological capacities. Hence, it would appear that wide content cannot be relevant to characterizing psychological equivalence, philosophers attached to externalist theories of content have sometimes attempted to introduce ‘narrow’ content, i.e., an aspect or kind of content that is equivalent in internally equivalent systems. The simplest such theory is Fodor’s idea (1987) that narrow content is a function from contexts (i.e., from whatever the external factors are) to wide contents.
 The actions made rational by content-involving states are actions individuated in part by reference to the agent’s relations to things and properties in his environment, wanting to see a particular movie and believing that building over there is a cinema showing it makes rational the action of walking in the direction of that building. Similarly, for the fundamental case of a subject who has knowledge about his environment, a crucial factor in masking rational the formation of particular attitudes is the way the world is around him. One may expect, then, that any theory that links the attributing of contents to states with rational intelligibility will be committed to the thesis that the content of a person’s states depends in part upon his relations to the world outside him we can call this thesis of externalism about content.
 Externalism about content should steer a middle course. On the one hand, the relations of rational intelligibility involve not just things and properties in the world, but the way they are presented for being - an externalist should use some version of Frége’s notion of a mode of presentation. Moreover, many have argued that there exists its ‘sense’, or ‘mode of presentation’ (something ‘intention’ is used as well). After all, ‘is an equiangular triangle  and is an equilateral triangle,  pick out the same things not only in the actual world, but in all possible worlds, and so refer - insofar as to the same extension, same intension and (arguably from a causal point of view) the same property, but they differ in the way these referents are presented to the mind. On the other hand, the externalist for whom considerations of rational intelligibility are pertinent to the individuation =of content is likely to insist that we cannot dispense with the notion of something in the world - an object, property or relation - being presented in a certain way, if we dispense with the notion of something external being presented in a certain way, we are in danger of regarding attributions of content as having no consequences for how an individual relates to his environment, in a way that is quite contrary to our intuitive understanding of rational intelligibility.
 Externalism comes in more and less extreme versions: Consider a thinker who sees a particular pear, and thinks a thought ‘that pear is ripe’, where the demonstrative way of thinking of the pear expressed by ‘that pear’ is made available to him by his perceiving the pear. Some philosophers, including Evans (1982) and McDowell (1984), have held that the thinker would be employing a different perceptually.  Based way of thinking were he perceiving a different pear. But externalism need not be committed to this, in the perceptual state that makes available the way of thinking, the pear is presented for being in a particular direction from the thinker, at a particular distance, and as having certain properties. A position will still be externalist if it holds that what is involved in the pear’s being so presented is the collective role of these components of content in making intelligible in various circumstances the subject’s relations to environmental directions, distances and properties of objects. This can be held without commitment to the object-dependence of the way of thinking expressed by ‘that pear’. This less strenuous form of externalism must, though, addressed the epistemological argument offered in favour of the more extreme versions, to the effect that only they are sufficiently world-involving.
 Externalism about content is a claim about dependence, and dependence comes in various kinds. The apparent dependence of the content of beliefs on factors external to the subject can be formulated as a failure of supervenience of belief content upon facts about what is the case within the boundaries of the subject’s body. In epistemology normative properties such as those of justification and reasonableness are often held to be supervening on the class of natural properties in a similar way. The interest of supervenience is that it promises a way of trying normative properties closely to natural ones without exactly reducing them to natural ones: It can be the basis of a sort of weak  naturalism. This was the motivation behind Davidson’s (1917-2003) attempt to say that mental properties supervene into physical ones - an attempt which ran into severe difficulties. To claim that such supervenience fails is to make a modal claim: That there can be two persons the same in respect of their internal physical states (and so in respect to those of their disposition that are independent of content-involving states), who nevertheless differ in respect of which beliefs there have. Putnam’s (1926- ) celebrated example of a community of Twin Earth, where the water-like substance in lakes and rain is not H2O, but some different chemical compound XYZ - ‘water’ - illustrates such failure of supervenience. A molecule-for-molecule replica of you on twin earth has beliefs to the effect that ‘water’ is thus-and-so. Those with any chemical beliefs on twin earth may well not have any beliefs to the effect that water is thus-and-so, even if they are replicas of persons on earth who do have such beliefs. Burge emphasized that this phenomenon extends far beyond beliefs about natural kinds.
 In the case of content-involving perceptual states, it is a much more delicate matter to argue for the failure of supervenience, the fundamental reason for this is that attribution of perceptual content is answerable not only to factors on the input side - what in certain fundamental cases causes the subject to be in the perceptual state - but also to factors on the output side - what the perceptual state is capable of helping to explain amongst the subject’s actions. If differences in perceptual content always involve differences in bodily described actions in suitable counterfactual circumstances, and if these different actions always have distinct neural bases, perhaps, there will after all be supervenience of content-involving perceptual states on internal states
 This connects with another strand in the abstractive imagination, least of mention, of any thinker who has an idea of an objective spatial world - an idea of a world of objects and phenomena which can be perceived but which are not dependent upon being perceived for their existence - must be able to think of his perception of the world as being simultaneously due to his position in the world, and to the condition of the world at that position. The very idea of a perceivable, objective spatial world brings with it the idea of the subject as being in the world, with the course of his perceptions due to his changing position in the world and to the more or less stable way the world is. That also, of perception it is highly relevant to his psychological self-awareness to have of oneself as a perceiver of the environment.
 However, one idea that has in recent times been thought by many philosophers and psychologists alike to offer promise in the connection is the idea that perception can be thought of as a species of information-processing, in which the stimulation of the sense-organs constitutes an input to subsequent processing, presumably of a computational form. The psychologist J.J. Gibson suggested that the senses should be construed as systems the function of which is to derive information from the stimulus-array, as to ‘hunt for’ such information. He thought, least of mention, that it was enough for a satisfactory psychological theory of perception that his logical theory of perception that his account should be restricted to the details of such information pick-up, without reference to other ‘inner’ processes such as concept-use. Although Gibson has been very influential in turning psychology away from the previously dominant sensation-based framework of ideas (of which gestalt psychology was really a special case), his claim that reliance on such a notion of information is enough has seemed incredible to many. Moreover, its notion of ordinary one to warrant the accusation that it presupposes the very idea of, for example, concept-possession and belief that implicates the claim to exclude. The idea of information espoused bu Gibson (though it has to be said that this claim has been disputed) is that of ‘information about’, not the technical one involved in information theory or that presupposed by the theory of computation.
 There are nevertheless important links between these diverse uses, however, when I enter most intimately into what I call myself, I always stumble on some particular perception or other, of heat or cold, light or shade, love or hatred, pain or pleasure. I never catch myself at any time without a perception and can never observe anything but the perception. However, the idea is that specifying the content of as perceptual experience involves saying what ways of filling out a space around the origin with surfaces, solids, textures, light and so forth, are consistent with the correctness or veridicality of the experience. Such contents are not built from propositions, concepts, senses or continuants of material objects.
 Where the term ‘content’ was once associated with the phrase ‘content of consciousness’ to pick out the subjective aspects of mental states, its use in the phrase ‘perceptual content’ is intended to pick out something more closely akin to its old ‘form’ the objective and publicly expressible aspects of mental states. The content of perceptual experience is how the world is represented to be. Perceptual experiences are then counted as illusory or veridical depending on whether the content is correct and the world is as represented. In as much as such a theory of perception can be taken to be answering the more traditional problems of perception. What relation is there between the content of a perceptual state and conscious experience? One proponent of an intentional approach to perception notoriously claims that it is ‘nothing but the acquiring of true or false beliefs concerning the current state of the organism’s body or environment, but the complaint remains that we cannot give an adequate account of conscious perception, given the ‘nothing but’ element of this account. However, an intentional theory of perception need not be allied with any general theory of ‘consciousness’, one which explains what the difference is between conscious and unconscious states. If it is to provide an alternative to a sense-data theory, the theory need only claim that where experience is conscious. Its content is constitutive, at least in part, of the phenomenological character of that experience. This claim is consistent with a wide variety of theories of consciousness, even the view that no account can be given.
 An intentional theory is also consistent with either affirming or denying the presence of subjective features in experience. Among traditional sense-data theorists of experience. H.H. Price attributed in addition an intentional content to perceptual consciousness. Whereby, attributive subjective properties to experience - in which case, labelled sensational properties, in the qualia - as well as intentional content. One might call a theory of perception that insisted that all features of what an experience is like ae determined by its intentional content, a purely intentional theory of perception.
 Mental events, states or processes with content include seeing the door is shut, believing you are being followed and calculating the square root of 2. What centrally distinguishes states, events or processes - henceforth, simply stares - with content  is that they involve reference to objects, properties or relations. A mental state exists a specific condition for a state with content a specific condition for a state with content to refer to certain things. When the state has correctness or fulfilment by whether its referents have the properties the content specifies for them.
 This highly generic characteristic of content permits many subdivisions. It does not in itself restrict contents to conceptualized content, and it permits contents built from Frége’s sense as well as Russellian contents built from objects and properties. It leaves open the possibility that unconscious states, as well as conscious states, have contents. It equally, allows the states identified by an empirical computational psychology to have content. A correct philosophical understanding of this general notion of content is fundamental not only to the philosophy of mind and psychology, but also to the theory of knowledge and to metaphysics.
 Perceptions make it rational for a person to form corresponding beliefs and  make it rational to draw certain inferences. Belief s and desire s make rational the formation of particular intentions, and the performance o the appropriate actions. People are frequently irrational of course, but a governing ideal of this approach is that for any family of content, there is some minimal core of rational transition to or from states involving them, a core that a person must respect if his states are to be attributed with those contents of all rational interpretative relations. To be rational, a set of beliefs, desires, and actions as well s perceptions, decisions must fit together in various ways. If they do not, in the extreme case they fail to constitute a mind at all - no rationality, no agent. This core notion of rationality in philosophy f mind thus concerns a cluster of personal identity conditions, that is, holistic coherence requirements upon the system of elements comprising a person’s mind, it is as well as in philosophy where it is often succumbing to functionalism about content and meaning appears to lead to holism. In general, transitions between mental states and between mental states and behaviour depend on the contents of the mental states themselves. In consideration that I infer from sharks being in the water to the conclusion that people shouldn’t be swimming. Suppose I first think that sharks are dangerous, but then change my mind, coming to think that sharks are not dangerous. However, the content that the first belief affirms can’t be the same as the content that the second belief denies, because the transition relations, e.g., the inference form sharks being in the water to what people should do, so, I changed mt mind functionalist reply is to say that some transitions are relevant to content individuation, whereby others are not. Appeal to a traditional analytic clear/synthetic distinction clearly won’t do. For example, ‘dogs’ ‘and cats’ would have the same content on such a view. It could not be analytic that dogs bark or that cats meow, since we can imagine a non-barking breed of dog and a non-meaning breed of cat. If ‘Dogs are animals’ is analytic, as ‘Cats are animals’. If ‘Cats are adult puppies ‘. Dogs are not cats - but then cats are not dogs. So a functionalist’s account will not find traditional analytic inferences of ‘dogs’ from the meaning of ‘cat’. Other functionalist accept  holism for ‘narrow content’, attempting to accommodate intuitions about the stability of content be appealing too wide content.
 Within the clarity made of inference it is unusual to find it said that, an inference is a (perhaps very complex) act of thought by virtue of which act (1) I pass from a set of one or more propositions or statements to a proposition or statement and (2) it appears that the latter is true in the former is or are. This psychological characterization has occurred widely in the literature under more of less inessential variations.
 It is natural to desire a better characterization of inference, but attempts to do so by construing a fuller psychological explanation fail to comprehend the grounds on which inference will be objectively valid - a point elaborated made by Gottlob Frége. And attempts to a better understand the nature about inference through the device of the representation of inference by formal-logical calculations to the informal inference they are supposed to represent or reconstruct, and (2) leaves us worried about the sense of such formal derivation. Are these derivations inferences? And aren’t informal inferences needed in order to apply the rules governing the constructions of forma derivation (inferring that this operation is an application of that formal rule)? These are concerns cultivated by, for example, of Wittgenstein. That, insofar as coming up with a good and adequate characterization of inference - and even working out what would count as a good and adequate characterization - is a hard and by no means nearly solved philosophical problem.
 It is still, of ascribing states with content to an actual person has to proceed simultaneously with attribution of a wide range of non-rational states and capacities. In general, we cannot understand a person’s reasons for acting as he does without knowing the array of emotions and sensations to which he is subject: What he remembers and what he forgets, an how he reasons beyond the confines of minimal rationality. Even the content-involving perceptual states, which play a fundamental role in individuating content, cannot be understood purely in terms relating to minimal rationality. A perception of the world as being a certain way is not (and could not be) under a subject’s rational control. Though it is true and important that perceptions give for forming beliefs, the beliefs for which they fundamentally provide reason - observational beliefs about the environment - have contents which can only be elucidated by inferring which can only be elucidated by inferring back to perceptual experience. In this respect (as in others), perceptual states defer from those beliefs and desires that are individuated by mentioning what they provide reasons for judging or doing: For frequently these latter judgements and actions can be individuate without reference back to the states that provide reasons for them.
 What is the significance for theories of content to the fact that it is almost certainly adaptive for members of a species to have a system of states with representational content which are capable of influencing their actions which are capable? According to teleological theories of content, a constitutive account of content - one which says what it is for a state to have a given content - must make use of the notions of natural function and teleology. The intuitive idea is that for a belie f state to have a given content ‘p’ is for the belief-forming mechanism which produced it to have the function (perhaps derivatively) of producing that state only when it is the case that ‘p’. But if content itself proves to resist elucidation in terms of natural function and selection, it is still a very attractive view that selection must be mentioned - such as a sentence - with a particular content, even though that content itself may be individuated by other means.
 Contents are normally specified by ‘that . . .’ clauses, and it is natural to suppose that a content has the same kind of sequential and hierarchical structure as the sentence that specifies it. This supposition would by widely accepted for conceptual content. It is, however, a substantive thesis that all content is conceptual. One way of treating one sort of perceptual content is to regard the content as determined by a spatial type, the type under which the region of space around the perceiver must fall if the experience with that content is to represent the environment correctly. The type involves a specification of surfaces and features in the environment, and their distances and direction from the perceiver’s body as origin. Supporters of the view that the legitimacy of using these spatial types in giving the content of experience does not undermine the thesis that all content is conceptual, such supporters will say that the spatial type is just a way of capturing what can equally be captured by conceptual components such as ‘that distance’, or ‘that direction’, where these demonstratives are made available by the perception in question.
 In specifying representative realism the significance this theory holds that (1) there is a world whose existence and nature is independent of it, (2) perceiving an object located in that external world necessarily involves causally interacting with that object, and (3) the information acquired in perceiving an object is indirect: It is information most immediately about the perceptual experience caused in us by the object, and only derivatively about the object itself. Traditionally, representative realism has been allied with an act/object analysis of sensory experience. In terms of representative realism, objects of perception (of which we are ‘independently aware’) are always distinct from objects of experience (of which we are ‘directly aware’) Meinongians, however, may simply that object of perception as existing objects of experience.
 Armstrong (1926- ) not only sought to explain perception without recourse to sense-data or subjective qualities but also sought to equate the intentionality of perception with that of belief. There are two aspects to this: the first is to suggest that the only attitude towards a content involved in perception is that of believing, and the second is to claim that the only content involved in perceiving is that which a belief may have. The former suggestion faces an immediate problem, recognized by Armstrong, of the possibility of having a perceptual experience without acquiring the correspondence belief. One such case is where the subject already possesses the requisite belief - rather than leading to the acquisition of, belief. The more problematic case is that of disbelief in perception. Where a subject has a perceptual experience but refrains from acquiring the correspondence belief. For example, someone familiar with Muller-Lyer illusion, in which lines of equal length appear unequal, is likely to acquire the belief that the lines are unequal on encountering a recognizable example of the illusion. Despite that, the lines may still appear unequal to them.
 Armstrong seeks to encompass such cases by talk of dispositions to acquire beliefs and talk of potentially acquiring beliefs. On his account this is all we need say to the psychological state enjoyed. However, once we admit that the disbelieving perceivers still enjoys a conscious occurrent experience, characterizing it in terms of a disposition to acquire a belief seems inadequate. There are two further worries. One may object that the content of perceptual experiences may play a role in explaining why a subject disbelievers in the first place: Someone may fail to acquire a perceptual belief precisely because how things appear to her is inconsistent with her prior beliefs about the world. Secondly, some philosophers have claimed that there can be perception without any correspondence belief. Cases of disbelief in perception are still examples of perceptual experience that impinge on belief: Where a sophisticated perceiver does not acquire the belief that the Müller-Lyer lines are unequal, she will still acquire a belief about how things look to her. Dretske (1969) argues for a notion of non-epistemic seeing on which it is possible for a subject to be perceiving something whole lacking any belief about it because she has failed to notice what is apparent to her. If we assume that such non-epistemic seeing, nevertheless, involves conscious experience e it would seem to provide another reason to reject Armstrong’s view and admit that if perceptual experiences are intentional states then they are a distinct attitude-type from that of belief. However, even if one rejects Armstrong’s equation of perceiving with acquiring beliefs or disposition to believe, one may still accept that he is right about the functional links between experience and belief, and the authority that experience has over belief, an authority which, can nevertheless be overcome.
 It is probably true that philosophers have shown much less interest in the subject of the imagination during the last fifteen tears or so than in the period just before that. It is certainly true that more books about the imagination have been written by those concerned with literature and the arts than have been written by philosophers in general and by those concerned with the philosophy of mind in particularly. This is understandable in that the imagination and imaginativeness figure prominently in artistic processes, especially in romantic art. Still, those two high priests of romanticism, Wordsworth and Coleridge, made large claims for the role played by the imagination in views of reality, although Coleridge’s thinking on this was influenced by his reading of the German philosopher of the late eighteenth and early nineteenth centuries, particularly Kant and Schelling. Coleridge distinguished between primary and secondary imagination, both of them in some sense productive, as opposed too merely reproductive. Primary imagination is involved in all perception of the world in accordance with a theory which, as Coleridge derived from Kant, while secondary imagination, the poetic imagination, is creative from the materials that perception provides. It is this poetic imagination which exemplifies imaginativeness in the most obvious way.
 Being imaginative is a function of thought, but to use one’s imagination in this way is not just a matter of thinking in novel ways. Someone who, like Einstein for example, presents a new way of thinking about the world need not be by reason of this supremely imaginative (though of course, he may be). The use of new concepts or a new way of using already existing concepts is not in themselves an exemplification of the imagination. What seems crucial to the imagination is that it involves a series of perspectives, new ways of seeing things, in a sense of ‘seeing’ that need not be literal. It thus involves, whether directly or indirectly, some connection with perception, but in different ways.  To make clear in the similarities and differences between seeing proper and seeing with the mind’s eye, as it is sometimes put. This will involve some consideration of the nature and role of images, least of mention, that there is no general agreement among philosophers about how to settle neurophysiological problems in the imagery of self.
 Connections between the imagination and perception are evident in the ways that many classical philosophers have dealt with the imagination. One of the earliest examples of this, the treatment of ‘phantasia’ (usually translated as ‘imagination’) in Aristotles ‘De Anima III. 3. seems to regard the imagination as a sort of half-way house between perception and thought, but in a way which makes it cover appearances in general, so that the chapter in question has as much to do with perceptual appearances, including illusions, as it ha s to do with, say. Imagery. Yet, Aristotle also emphasizes that imagining is in some sense voluntary, and that when we imagine a terrifying scene we are not necessarily terrified, any more than we need  be when we see terrible things in a picture. How that fits in with the idea that an illusion is or can be a function of the imagination is less than clear. Yet, some subsequent philosophers, Kant on particular. Followed in recent times by P.F. Strawson have maintained that all perception involves the imagination, in some sense of that term, in that some bridge is required between abstract thoughts and their perceptual instance. This comes out in Kant’s treatment of what he calls the ‘schematism’, where he rightly argues that someone might have an abstractive understanding of the concept of a dog without being able to recognize or identify any dogs. It is also clear that someone might be able to classify all dogs together without any understanding of what a dog is. The bridge that needs to be provided to link these two abilities Kant attributes to the imagination.
 In so arguing Kant goes, as he so often does, beyond Hume who thought of the imagination in two connected ways. Firs t, there is the fact that there exist. Hume thinks, ideas which are either copies of impressions provided by the senses or are derived from these. Ideas of imagination are distinguished from those of memory, and both of these from impression and sense, by their lesser vivacity. Second, the imagination is involved in the processes, mainly associated of ideas, which take one form on ideas to another, and which Hume uses to explain, for example, our tendency to think of objects as having no impression on them, ideas or less images, is the mental process which takes one from one idea to another and thereby explains our tendency to believe things go beyond what the senses immediately justify. The role which Kant gives to the imagination in relation to perception in general is obviously a wider and fundamental role than that Hume allows. Indeed,  one might take Kant to be saying that were there not the role that he, Kant insists on there would be no place for the role which Hume gives it. Kant also allows for a free use of the imagination in connection with the arts and the perceptions of beauty, and this is a more specified role than that involved in perception overall.
 In the retinal vision by the seeing of things we normally see them as such-and-such, is to be construed and in how it relate s to a number of other aspects of the mind ‘s functioning - sensation, concept and other things of other aspects of the mind’s functioning  - sensation, concepts, and other things involved in our understanding of things, belief and judgement, the imagination, our action is related to the world around us, and the causal processes involved in the physics, biology and psychology of perception. Some of the last were central to the considerations that Aristotle raised about perception in his ‘De Anima’.
 Nevertheless, there are also special, imaginative ways of seeing things, which Wittgenstein (1889-1951) emphasized in his treatment of ‘see-as’ in his ‘Philosophical Investigations II. Xi. And on a piece paper as standing up, lying down, hanging from its apex and so on is a form of ‘seeing-as’ which is both more special and more sophisticated than simply seeing it as a triangle. Both involve the application of concepts to the objects of perception, but the way in which this is done in the two cases is quite different. One might say that in the second case one has to adopt a certain perceptive, a certain point of view, and if that is right it links up with what had been said earlier about the relation and difference between thinking imaginatively and thinking in novel ways.
 Wittgenstein (1953) used the phrase ‘an echo of a thought is sight’ in relation to these special ways of seeing things, which he called ‘seeing aspects’. Roger Scruton has spoken of the part played in it all by ‘unasserted thought’, but the phrase used by Wittgenstein brings out more clearly one connection between thought and a form of sense-perception. Wittgenstein *1953) also compares the concepts of an aspect and that of seeing-as with the concept of an image, and this brings out a point about the imagination that has not been much evident in what has been said so far - that imagining something is typically a matter of picturing it in the mind and that this involves images in some way, however, the picture view of images has come under heavy philosophical attack. First, there have been challenges to the sense of the view: Mental images are not with real eyes: They cannot be hung on real walls and they have no objective weight or colour. What, the, can it mean to say, that images are pictorial? Secondly, there have been arguments that purport to show that the view is false. Perhaps, the best known of these is founded on the charge that the picture theory cannot satisfactorily explain the independency of many mental images. Finally, there have been attacks on the evidential underpinning of the theory. Historically, the philosophical claim that images are picture-like rested primarily on an appeal to introspection. And today less about the mind than was traditionally supposed. This attitude towards introspection has manifested itself in the case of imagery in the view that what introspection really shows about visual images is not that they are pictorial but only that what goes on in imagery is experimentally much like what goes on in seeing. This aspect is crucial for the philosophy of mind, since it raises the question of the status of images, and in particular whether they constitute private objects or stares in some way. Sartre (1905-80), in his early work on the imagination emphasized, following Husserl (1859-1938), that images are forms of consciousness of an object, but in such a way that they ‘present’ the object as not being: Wherefore, he said, the image ‘posits its object as nothingness’, such a characterization brings out something about the role of the form of consciousness of which the having of imagery may be a part, in picturing something the images are not themselves the object of consciousness. The account does less, however, to bring out clearly just what images are or how they function.
 As part of an attemptive grappling about the picturing and seeing with the mind’s eye, Ryle (1900-76 ), has argued that in picturing, say, Lake Ontario, in having it before the mind’s eye, we are not confronted with a mental picture of Lake Ontario: Images are not seen. We nevertheless, can ‘see’ Lake Ontario, and the question is what this ‘seeing’ is, if it is not seeing in any direct sense. One of the things that may make this question difficult to answer is the fact that people’s images and their capacity for imagery vary, and this variation is not directly related to their capacity for imaginativeness. While an image may function in some way as a ‘presentation’ in a train of imaginative thought, such thought does not always depend on that: Images may occur in thought which are not really representational at all, are not, strictly speaking, ‘of’ anything. If the images are representational, can one discover things from one’s images that one would not know from  otherwise? Many people would answer ‘no’, especially if their images are generally fragmentary, but it is not clear that this is true for everyone. What is more, and this affects the second point, fragmentary imagery which is at best ancillary to process of though in which it occurs may not be in any obvious sense representational, even if the thought itself is ‘of’ something.
 Another problem with the question what it is to ‘see’ Lake Ontario with the mind’s eye is that the ‘seeing’ in question may or may not be a direct function of ‘memory’. For one who has seen Lake Ontario, imaging it may be simply a matter of reproduction in some form in the original vision, and the vision may be reproduced unintentionally and without any recollection of what it is a ‘vision’ of. For one who has never been it the task of imagining it depends most obviously on the knowledge of what sort of thing Lake Ontario is and perhaps on experiences which are relevant to that knowledge. It would be surprising, to say the least, if imaginative power could produce a ‘seeing’ that was not constructed from any previous seeing. But that the ‘seeing’ is not itself a seeing in the straightforward sense is clear, and on this negative point what Ryle says, and other s have said, seems clearly right. As to what ‘seeing’ is in a positive way, Ryle answers that it involves fancying something and that this can be assimilated to pretending. Fancying that one is seeing Lake Ontario is thus, at least, like pretending that one is doing that thing. But is it?
 Along the same course or lines, there is in fact a great difference between say, imaging that one is a tree and pretending to be a tree. Pretending normally involves doing something, and even when there is no explicit action on the part of the pretender, as when he or she pretends that something or other is the case, there is at all events an implication of possible action. Pretending to be a tree may involve little more that standing stock-still with one’s arms spread out like branches. To imagine being a tree (something that is founded that some people deny being possible, which is to my mind a failure of imagination) need imply no action whatever, (Imagining being a tree is different in this respect from imagining that one is a tree, where this means believing falsely, that one is a tree, one can imagine being a tree without this committing one to any beliefs on that score). Yet, of imagining being a tree does seem to involve adopting the hypothetical perspective of a tree, contemplating perhaps, that it is like to be a fixture in the ground with roots growing downward and with branches (somewhat like arms) blown by the wind and with birds perching on them.
 Imagining something seems in general to involve change of identity on the part of something or other, and in imagining being something else, such as a tree, the partial change of identity contemplated is in oneself. The fact that the change of identity contemplated cannot be completely does not gainsay, the point that it is a change of identity which is being contemplated. One might raise the question whether something about the ‘self’ is involved in all imaginings. Berkeley (1685-17530 even suggests that imagining a solitary unperceived tree involves a contradiction, in that a imagine that is to imagine oneself perceiving it.  In fact, there is a difference between imagining a object, solitary or not, and imagining oneself seeing that object. The latter certainly involves putting themselves imaginatively in the situation pictured: The former involves contemplating the object from a point of view that from that point of view which one would oneself have if one were viewing that point of view to which reference has already been made, in a way that clearly distinguishes picturing something from merely thinking of it.
 This does not rule out the possibility that an imagine might come into one’s mind which one recognizes as some kind of depiction of a scene. But when actually picturing a scene, it would not be right to say that one imagines the scene by way of a contemplation of an image which plays the part of as picture of it. Moreover, it is possible to imagine a scene without any images occurring, the natural interpretation of which would be that they are pictures of that scene. It is possible for one imagining say, the GTA is to report on request the occurrences of images which are not in any sense pictures of the GTA -, not of that particular city and perhaps not even of a city at all. That would not entail that he or she was not imagining the GTA: A report to or associated with the GTA, thought by others to be of the GTA.
 This raises a question which is asked by Wittgenstein (1953) -, ‘What makes my image of him into an image of him’? To which Wittgenstein replies ‘Not its looking like him’, and furthering  he suggests that a person’s account of what his imagery represents is decisive. Certainly it is so when the process of imagination which involves the imagery is one that the person engages in intentionality. The same is not true, as Wittgenstein implicitly acknowledges in the same context, if the imagery simply comes to mind without there being any intention, in that case, one might not even know what the image is an image of.
 Nevertheless, all this complicates the question what the status of mental images is. However, it might seem that they stand in relation to imagining as ‘sensations’ stand to perception, except that the occurrence of sensations is a passive set-organization of specific presentiments, while the occurrence of an image can be intentional, and in the context of an active flight of imagination is likely to be so. Sensations give perceptions a certain phenomenal character, providing they’re sensuous, as opposed to conceptual content.  Intentional action has interesting symmetric and asymmetric to perception. Like perceptual experience, the experiential component of intentional action is causally self-referential. If, for example, I can now walking to my car, then the condition of satisfaction of the preset experience is that there be certain bodily movements, and that this very experience of acting cause those bodily movements. Furthering, like perceptual experience, the experience of acting is topically a conscious mental event, is that perception is always concept-dependent at least in the sense that perceivers must be concept possessors and users, and almost certainly the sense that perception entails concept-use in its application to objects. It is, at least, arguable that those organisms that react in a biologically useful way to something but that are such that the attribution of concepts them is implausible, should not be said to perceive those objects, however, much the objects figure causally in their behaviour. There are, nevertheless, important links between these diverse uses. We might call a theory which attributes to perceptual states as content in the new sense as ‘an intentional theory’ of perception. On such a view, perceptual states represent to the subject how her environment and body are. The content of perceptional experiences is how the world is presented to be. Perceptual experiences are then counted as illusory or veridical depending on whether the content is correct and the world is as represented. In as such as such a theory of perception can be taken to be answering the more traditional problems of perception, such will deal with the content of consciousness. The ruminative contemplation, where with concepts looms largely and has, perhaps the overriding role, it still seems necessary for our thought to be given a focus in thought-occurrences such as images. These have sometimes been characterized as symbols which are the material of thought, but the reference to symbols is not really illuminating. Nonetheless, while a period of thought in which nothing of this kind occurs is possible, the general direction of thought seems to depend on such things occurring from time to time. The necessary correlations that are cognizant, insofar as when  we get a feeling, or an ‘impression’, thereof: Which of us attribute a necessity to the relation between things of two particular kinds of things. For example, an observed correlation between things of two kinds can be seen to produce in everyone a propensity to expect a thing to the second sort given an experience of a thing on the first sort. That of saying, there is no necessity in the relations between things that happen in the world, but, given our experience and the way our minds naturally work, we cannot help thinking that there is. In the case of the imagination images seem even more crucial, in that without therm it would be difficult, to say, at least, for the point of view or perspective which is important for the imagination to be given a focus.
 Of the same lines that it would be difficult for this to be so, than impossible, since it is clear that entertaining a description of a scene, without there being anything that a vision of it, could sometimes give that perceptive. The question still arises whether a description could always do quite what an image can do in this respect. The point is connected with an issue over which there has been some argument among psychologists, such as S.M. Kosslyn and Z.W. Pylyshyn, concerning what are termed ‘analogue’ versus ‘propositional’ theories of representation. This is an argument concerning whether the process of imagery is what Pylyshyn (1986) calls ‘cognitively penetrable’, i.e., such that its function is affected by beliefs or other intellectual processes expressible in propositions, or whether, it can be independent of cognitive processes although capable itself of affecting the mental life because of the pictorial nature of images ( the ‘analogue medium’). One example, which has embarked upon that argument, is that in which people are asked whether two asymmetrically presented figures can be made to coincide, the decision on which may entail some kind of material rotation of one or more of the figures. Those defending the ‘analogue’ theory, point to the fact that there is some relation between the time taken and the degree of the rotation required, this suggests that some processes involving changing images is identify with. For some who has little or no imagery this suggestion, may seem unintelligible. Is it enough for one to go through an intellectual working out of the possibilities, as based on features of the figures that are judged relevant? This could not be said to be unimaginative as long as the intellectual process involved reference to perceptive or points of view in relation to the figures, the possibility of which the thinker might be able to appreciate. Such an account of the process of imagination cannot be ruled out, although there are conceivable situations in which the ‘analogue’ process of using images might be easier. Or, at least, it might be easier for those who have imagery most like the actual perception of a scene: For others situation might be difficult.
 The extreme of the former position is probably provided by those who have so-called ‘eidetic’ imagery, where having an image of a scene is just like seeing it, and where, if it is a function of memory as it most likely is, it is clearly possible to find out details of the scene imagined by introspection of the image. The opposite extreme is typified by those for whom imagery, to the extent it occurs at all, is at best ancillary to propositionally styled thought. But, to repeat the point made unasserted, will not count as imagination unless it provides a series of perspectives on its object. Because images are or can be perceptual analogues and have a phenomenal character analogous to what sensations provide in perception they are ,most obviously suited. In the working of the mind, to the provision of those perspectives. Bu t in a wider sense, imagination enters the picture whenever some link between thought and perception is required, as well as making possible imaginative forms of seeing-as. It may thus justifiably be regarded as a bridge between perception and thought.
 The plausibility to have a firm conviction in the reality of something as, perhaps, as worthy of belief and have no doubt or unquestionably understood in the appreciation to view as plausible or likely to apprehend the existence or meaning of comprehensibility whereas, an understandable vocation as to be cognizant of things knowably sensible. To a better understanding, an analogous relationship may prove, in, at least, the explanation for the parallels that obtain between the ‘objects of contents of speech acts’ and the ‘objects or contents of belief’. Furthermore, the object of believing, like the object of  saying, can have semantic properties, for example:
What Jones believes is true.
And:
What Jones believes entails what Smith believes.
One plausible hypophysis, then, is that the object of belief is the same sort of entity as what is uttered in speech acts (or what is written down).
 The second theory also seems supported by the argument of which our concerns conscribe in the determination of thought, for which our ability to think certain thoughts appears intrinsically connected with the ability to think certain others. For example, the ability to think that John hit Mary goes hand in hand with the ability to think that Mary hits John, but not with the ability to think that Toronto is overcrowded. Why is this so? The ability to produce or understand certain sentences is intrinsically connected with the ability to produce or understand certain others. For example, there are no native speakers of English who know how to say ‘John hits Mary’, but who do not know how to say ‘Mary hits John’. Similarly, there are no native speakers who understand the former sentence but not the latter. These facts are easily explained if sentences have a syntactic and semantic structure, but if sentences are taken to be atomic, these facts are a complete mystery. What is true for sentences is true also for thoughts. Thinking thoughts involving manipulating mental representations. If mental representations with a propositional content have a semantic and syntactic structure like that of sentences. It is no accident that one who is able to think that John hits Mary is thereby, able to think that Mary hits John. Furthermore, it is no accident that one who can think these thoughts need not thereby be able to think thoughts, having different components - for example, the thought that Toronto is overcrowded. And what goes here for thought goes for belief and the other propositional  attitudes.
 If concepts of the simple (observational) sort were internal physical structures that had in this sense, an information-carrying function, a function they acquired during learning, then instances as such types would have a content that (like a belief) could be either true or false. After learning, tokens of these structure types, when caused by some sensory stimulation, would ‘say’ (i.e., mean) what it was their function to ‘tell’ (inform about). They would therefore, quality as beliefs - at least of the simple observational sort.
 Any information-carrying structure carries all kinds of information. If, for example, it carriers information ‘A’, it must also carry the information that ‘A’ or ‘B’. As I conceived of it, learning was supposed to be a process in which a single piece if this information is selected for special treatment, thereby becoming the semantic content - the meaning - of subsequent tokens of that structure type. Just as we conventionally give artefacts and instruments information-providing functions, thereby making their activities and states - pointer readers, flashing lights, and so on - representations of the conditions, so learning converts neural states that carry information - ‘pointers readers’ in the head, so to speak - into structures that have the function to providing some vital piece of the information they carry are also presumed to serve as the meanings of linguistic items, underwriting relations of translation, definition, synonymy, antinomy and semantic implications. Much work in the semantics of natural language takes itself to be addressing conceptual structure.
 Concepts have also been thought to be the proper objects of ‘philosophical analysis’. ‘Analytic’ philosophers when they ask about the nature of justice, knowledge or piety and expect to discover answers by means of introspective reflection, yet the expectation that one sort of thing could serve all these tasks went hand in hand with what has come to be called the ‘Classical View’ of concepts, according of conditions that are individually necessary and jointly sufficient for their satisfaction, which are known to any competent user of them, the standard example is the especially simple one [bachelor], which seems to be identified to [eligible unmarried male]. A more interesting, but problematic one has been [knowledge], whose analysis was traditionally thought to be [justified true belief].
 The notional representation that treat relations as a subclass of property brings to contrast with property is ‘concept’, but one must be very careful, since ‘concept’, has =been used by philosophers and psychologists to serve many different purposes. One use has it that certain factors of conceiving of some aspect of the world. As such, concepts have a kind of subjectivity as having to contain the different individuals might, for example, have different concepts of birds, one thinking of them primarily as flying creatures and the other as feathered. Concepts in this sense are often described as a species of ‘mental representation’, and as such they stand in sharp contrast to the notion of a property, since a property is something existing in the world. However, it is possible to think of a concept as neither mental nor linguistic and this would allow, though it doesn’t dictate, that concepts and properties are the same kind of thing. Nonetheless, the function of learning is naturally to develop, as things inasmuch as they do, in some natural way, either (in the case of the senses) from their selectional history or (in the casse of thought) from individual learning. The result is a network of internal representations that have, in different ways, the power to represent: Experiences and beliefs.
 This does, however, leave a question about the role of the senses in this total cognitive enterprise. If it is learning that, by way of concepts, is the source of the representational powers of thought, from whence comes the representational powers of experience? Or should we even think of experience in representational terms? We can have false beliefs, but are there false experiences? On this account, then, experience and thought are both representational. The difference resides in the source of heir representational powers, learning in the case of thoughts, evolution in the case of experience.
 Though, perception is always concept-dependent, at least in the sense that perceivers must be concept possessors and users, and almost certainly in the sense that perception entails concept-use in its application to objects. It is at least, arguable that those organisms that react in a biologically useful way to something, but that are such that the attribution of concepts to them is implausible, should not be said to perceive those objects, however, much is as there is much that the object figures causally in their behaviour. Moreover, that consciousness presents the object in such a way that the experience has certain phenomenal character, which derived from the sensations which the causal processes involved set up. This is most evident is the case of ‘touch’ (which being a ‘contact sense’ provides a more obvious occasion for speaking of sensations than do ‘distance senses’ such as sight). Our tactual awareness of the texture of a surface is, to use a metaphor, ‘coloured’ by the nature of the sensations that the surface produces in our skin, and which we can be explicitly aware of if our attention is drawn to them (something that gives one indication of how attention too is involved in perception).
 It has been argued, that the phenomenal character of n experience is detachable from its contentual content in the sense that an experience of the same phenomenal character could occur even if the appropriate concepts were not available. Certainly the reverse is true - that a concept-mediated awareness of an object could occur without any sensation-mediated experience - as in an awareness of something absent from us. It is also the case, however, that the look of something can be completely changed by the realization that it is to be seen as ‘χ’ rather than ‘y’. To the extent that, which is so, the phenomenal character of a perceptual experience should be viewed as the result of the way in which sensations produced in us by objects blend with our ways of thinking of and understanding those objects (which, it should be noted, are things in the world and should not be confused with the sensations which they produce).
 In the study o ff other parts of the natural world, we agree to be satisfied with post-Newtonian ‘best theory’ arguments: There is no privileged category of evidence that provides criteria for theoretical constructions. In the study of humans above the neck, however, naturalistic theory does not suffice: We must seek ‘philosophical explanations’, require that theoretical posits specified terms of categories of evidence selected by the philosopher (as, in the radically upon unformulated notions such as ‘access in principle’ that have no place in naturalistic inquiry.
 However, one evaluates these ideas, that clearly involve demands beyond naturalism, hence, a form of methodological/epistemological dualism. In the absence of further justification, it seems to me fair to conclude, that inability to provide ‘philosophical explanation’ or a concept of ‘rule-following’ that relies on access to consciousness (perhaps  ‘in principle’) is a merit of a naturalistic approach, not a defect.
 A standard paradigm in the study of language, given its classic form by Frége, holds that there is a ‘store of thoughts’ that is a common human possession and a common public language in which these thoughts are expressed. Furthermore, this language is based on a fundamental relation between words and things - reference or denotation - along with some mode of fixing reference )sense, meaning). The notion of a common public language has never been explained, and seems untenable. It is also far from clear why one should assume the existence of a common store of thoughts: The very existence of thoughts had been plausibly questioned, as a misreading of surface grammar, a century earlier.
 Only those who share a common world can communicate, only those who communicate can have the concept of an inter-subjective, objective world. As a number of things follow. If only those who communicate have the concept of an objective world, only those who communicate can doubt whether an external world exists. Yet I is impossible seriously (consistently) to doubt the existence of other people with thoughts, or the existence of an external world, since to communicate is to recognize the existence of other people in a common world. Language, that is, communication with others, is thus essential to propositional thought. This is not because it is necessary to have the words to express a thought (for it is not); it is because the ground of the sense of objectivity is inter-subjectivity, and without the sense of objectivity, of the distinction between true and false, between what is thought to be and what is the case, there can be nothing rightly called ‘thought’.
 Since words are also about things, it is natural to ask how their intentionality is connected in that of thoughts. Two views have been advocated: One view takes thought content to be self-subsistent relative to linguistic content, with the latter dependent on or upon the former. The other view takes thought content to be derivative upon linguistic content, so that there can be no thought without a bedrock of language. Appeals to language at this point are apt to founder on circularity, since words take on the powers of concepts only insofar as there express them. Thus, there seems little philosophical illumination to be got from making thought depend upon language. Nonetheless, it is not entirely clear what it amounts to assert or deny, that there is an inner language of thought. If it means merely that concepts (thought-constituents) are structured in such a way as to be isomorphic with spoken language, then the claim is trivially true, given some natural assumption. But if it means that concepts just are ‘syntactic’ items orchestrated into strings of the same, then the claim is acceptable only in so far as syntax is an adequate basis for meaning - which, on the face of it, it is not. Concepts n doubt have combinatorial powers comparable to those of words, but the question is whether anything else can plausibly be meant by the hypothesis of an inner language.
 Yet, it appears undeniable that the spoken language does not have autonomous intentionality, but instead derives its meaning from the thoughts of speakers - though language may augment one’s conceptual capacities. So thought cannot post-date spoken language. The truth seems to be that in human psychology speech and thought are interdependent in many ways, but that there is no conceptual necessity about this. The only ‘language’ on which thought essentially depends is that of the structured system of concepts itself: Thought depends on or upon there being isolable concepts that can join with others to produce complete propositions. But this is merely to draw attention to a property of any system of concepts must have; it is not to say what concepts are or how they succeed in moving between thoughts as they do.
 Finally, there is the old question of whether, or to what extent, a creature who does not understand a natural language can have thoughts. Now it seems pretty compelling that higher mammals and humans raised without language have their behaviour controlled by mental states that are sufficiently like our beliefs, desires and intentions to share those labels. It also seems easy to imagine non-communicating creatures who have sophisticated mental lives (they build weapons, dams, bridges, have clever hunting devices, etc.). at the same time, ascriptions of particular contents to non-language-using creatures typically seem exercises in loose speaking (does the dog really believe that there is a bone in the yard?), and it is no accident that, as a matter of fact, creatures who do not understand a natural language have at best primitive mental lives. There is no accepted explanation of these facts. It is possible that the primitive mental failure to master natural languages, but the better explanation may be Chomsky’s, that animals lack a special language faculty to our species, as, perhaps, the insecurity that is felt, may at best resemble the deeper of  latencies that cradles his instinctual primitivities, that have contributively distributed the valuing qualities that amount in the result to an ‘approach-avoidance’ theory. As regards the wise normal human raised without language; this might simply be due to the ignorance and lack of intellectual stimulation such a person would be predetermined to. It also might be that higher thought requires a neural language with a structure comparable to that of a natural language, and that such neural languages are somehow acquired: As the child learns its native language. Finally, the ascription states of languageless creatures is a difficult topic that needs more attention. It is possible that as we learn more about the logic of our ascriptions of propositional content, we will realize that these ascriptions are egocentrically based on a similarity to the language in which we express our beliefs. We might then learn that we have no principled basis for ascribing propositional content to a creature who does not speak something a lot like one of our natural languages, or who does not have internal states with natural-language-like structure.  It is somewhat surprising how little we know about thought’s dependence on language.
 The relation between language and thought is philosophies chicken-or-egg problem. Language and thought are evidently importantly related, but how exactly are they related? Does language come first and make thought possible, or is it vice versa? Or are they on a par, each making the other possible.
 When the question is stated this generally, however, no unqualified answer is possible. In some respects thought is prior, and in other respects neither is prior. For example, it is arguable that a language is an abstract pairing of expressions and meaning, a function in the set-theoretic sense from expressions onto meaning. This makes sense of the fact that Esperanto is a language no one speaks, and it explains why it is that, while it is a contingent fact that ‘La neige est blanche’ means that snow is white among the French. It is a necessary truth that it means that in French. But if natural languages such as French and English are abstract objects in this sense, then they exist in possible worlds in which there are no thinkers in this respect, then, language as well as such notions as meaning and truth in a language, is prior to thought.
 But even if languages are construed as abstract expression-meaning pairings, they are construed that way as abstractions from actual linguistic practice - from the use of language in communicative behaviour - and there remains a clear sense in which language is dependent on thought. The sequence of inscribes ‘Naples is south of Rome’ means among us that Naples is south of Rome. This is a contingent fact, dependent on the way we use ‘Naples’. Rome and the other parts of that sentence. Had our linguistic practices been different, ‘Naples is south of Rome’ means among us that Naples is south of Rome has something to do with the beliefs and intentions underlying our use of the words and structures that compose the sentence. More generally, it is a platitude that the semantic features that inscribes and sounds have in a population of speakers are, at least, partly determined by the ‘propositional attitudes’ those speakers have in using those inscriptions and sounds or in using the parts and structures that compose them. This is the same platitude, of course, which says that meaning depends at least partly on use: For the use in question is intentional use in communicative behaviour. So, here, is one clear sense in which language is dependent on thought: Thought is required to imbue inscriptions and sounds with the semantic features they have in populations of speakers.
 The sense in which language does depend on thought can be wedded to the sense ion which language does not depend on thought in the ways that: We can say that a sequence of ascriptions or sounds (or, whatever) σ means ‘q’ in a language ‘L’, construed as a function from expressions onto meaning, iff L(σ) = q. this notion of meaning-in-a-language, like the notion of a ;language, is a mere set-theoretic notion that is independent of thought in that it presupposes nothing about the propositional attitudes of language users: σ can mean ‘q’ in ‘L’ even if ‘L’ has never been used? But then we can say that σ also means ‘q’ in a population ‘P’ jus t in case members of ‘P’ use some language in which σ ,means ‘q’: That is, just in case some such language is a language of ‘P’. The question of moment then becomes: What relation must a population ‘P’ bear to a language ‘L’ in order for it to be the case that ‘L’ is a language of ‘P’, a language members of ‘P’ actually speak? Whatever the answer to this question is, this much seems right: In order for a language to be a language of a population of speakers, those speakers in their produce sentences of the language in their communicative behaviour. Since such behaviour is intentional, we know that the notion of a language
‘s being the language of a population of speakers presupposes the notion of thought. And since that notion presupposes the notion of thought, we also know that the same is true of the correct account of the semantic features expressions have in populations of speakers.
 This is a pretty thin result, not one likely to be disputed, and the difficult questions remain. We know that there is some relation ‘R’ such that a language ‘L’ is used by a population ‘P’ iff ‘L’ bears ‘R’ to ‘P’. Let us call this relation, whatever it turns out to be, the ‘actual-language reflation’. We know that to explain the actual-language relation is to explain the semantic features expressions have among those who are apt to produce those expressions. And we know that any account of the relation must require language users to have certain propositional attitudes. But how exactly is the actual language relation to be explained in terms of the propositional attitude of language users? And what sort of dependence might those propositional attitudes in turn have those propositional attitudes in turn have on language or on the semantic features that are fixed by the actual-language relation? Let us, least of mention, begin once again, as in the relation of language to thought, before turning to the relation of thought to language.
 All must agree that the actual-language relation, and with it the semantic features linguistic items have among speakers, is at least, partly determined by the propositional attitudes of language users. This still leaves plenty of room for philosophers to disagree both about the extent of the determination and the nature of the determining propositional attitude. At one end of the determination spectrum, we have those who hold that the actual-language relation is wholly definable in terms of non-semantic propositional attitudes. This position in logical space is most famously occupied by the programme, sometimes called ‘intention-based semantics’, of the late Paul Grice and others. The foundational notion in this enterprise is a certain notion of speaker meaning. It is the species of communicative behaviour reported when we say, for example, that in uttering ‘ll pleut’, Pierre meant that it was raining, or that in waving her hand, the Queen meant that you were to leave the room, intentional-based semantics seeks to define this notion of speaker meaning wholly in terms of communicators’ audience-directed intentions and without recourse to any semantic notion. Then it seeks to define the actual-language relation in terms of the now-defined notion of speaker meaning, together with certain ancillary notions such as that of a conventional regularity or practice, themselves defined wholly in terms of non-semantic propositional attitudes. The definition of the actual-language relation in terms of speaker meaning will require the prior definition in terms of speaker meaning of other agent-semantic notions, such as the notions of speaker reference and notions of illocutionary act, and this, too, is part of the intention-based semantics.
 Some philosophers object to the intentional-based semantics because they think it precludes a dependence of thought on the communicative use of language. This is a mistake. Even if the intentional-based semantic definitions are given a strong reductionist reading, as saying that public-language semantic properties (i.e., those semantic properties that supervene on use in communicative behaviour) it might still be that one could not have propositional attitudes unless one had mastery of a public-language. However, our generating causal explanatory y generalizations, and subject to no more than the epistemic indeterminacy of other such terms. The causal explanatory approach to reason-giving explanations also requires an account of the intentional content of our psychological states, which makes it possible for such content to be doing such work. By the early 1970s, and many physicalists looked for a way of characterizing the primary and priority of the physical that is free from reductionist implications. As we have in attestation, the key attraction of supervenience to physicalists has been its promise to deliver dependence without reduction. For example, of moral theory has seemed encouraging as Moore and Hare, who made much of the supervenience of the moral on the naturalistic, were at the same time, strong critics of ethical naturalism, the principal reductionist position in ethical theory. And thee has been a broad consensus among ethical theorists that Moore and Hare were right, that the moral, or more broadly the normative, is supervening on the non-moral without being reducible to it. Whether or not this is plausible (that is a separate question), it would be no more logically puzzling than the idea that one could not have any propositional attitudes unless one had one’s with certain sorts of contents. there is no pressing reason to think that the semantic needs to be definable in terms of the psychological. Many intention-based semantic theorists have been motivated by a strong version of ‘physicalism’, which requires the reduction of all intentional properties (i.e., all semantic and propositional-attitude properties) too physical , or at least, topic-neutral or functional properties, for it is plausible that there could be no reduction of the semantic and the psychological to the physical without a prior reduction of the semantic to the psychological. But it is arguable that such a strong version of physicalism is not what is required in order to fit the intentional into the natural order.
 So, the most reasonable view about the actual-language relation is that it requires language users to have certain propositional attitudes, but there is no prospect of defining the relation wholly in terms of non-semantic propositional attitudes. It is further plausible  that any account of the actual-language relation must appeal to speech acts such as speaker meaning, where the correct account of these speech acts is irreducibly semantic (they will fail to supervene on the non-semantic propositional altitudes of speakers in the way that intentions fail to supervene on an agent’s beliefs and desires). If this is right, it would still leave a further issue about the ‘definability’ of the actual-language relation, and if so, will any irreducibly semantic notions enter into that definition other than the sorts of speech act notions already alluded to? These questions have not been much discussed in the literature as there is neither an established answer nor competing school of thought. Such that the things in philosophy that can be defined, and that speech act notions are the only irreducibly semantic notions the definition must appeal to.
 Our attention is now to consider on or upon the dependence of thought on language, as this the claim that propositional attitudes are relations to linguistic items which obtain at least, partly by virtue of the content those items have among language users. This position does not imply that believers have to be language users, but it does make language an essential ingredient in the concept of belief. However, we might then learn that we have no principled basis for ascribing propositional content to who does not speak something, a lot like, does not have internal states with natural-language-like structure. It is somewhat surprising how little we know about thought’s dependence on language.
 The Scottish philosopher, born in Edinburgh, David Hume (1711-76 ) whose theory of knowledge starts from the distinction between perception and thought. When we see, hear, feel, etc. (In general, perceive) something we are ware of something immediately present to the mind through the senses. But we can also think and believe and reason about things which are not present to our senses at the time, e.g.,  objects and events in the past, the future or the present beyond our current perceptual experience. Such beliefs make it possible for us too deliberate and so act on the basis of information we have acquired about the world.
 For Hume all mental activity involves the presence before the mind o some mental entity. Perception is said to differ for thought only in that the kinds of things that are present to the mind in each case are present to the mind in each case are different. In the case of perception it is an ‘impression’: In the case of thought, although what is thought about is absent, what is present to the mind is an ‘idea’ of whatever is thought about. The only difference between an impression and its corresponding idea is the greater ‘force and liveliness’ with which it ‘strikes upon the mind’.
 All the things that we can think or believe or reason about are either ‘relations of ideas’ or ‘matters of fact’. Each of the former (e.g., that three times five equals half of thirty) holds necessarily: Its negation implies a contradiction, such truths are ‘discoverable by the operation of pure thought, without dependence on what is anywhere existent in the universe. Hume has no systematic theory of this kind of knowledge: What is or is not included in a given idea, and how we know whether it is, is taken as largely unproblematic. each ‘matter of fact’ is contingent: Its negation is distinctly conceivable and represents a possibility. That the sun will not rise tomorrow is no less intelligible and no more implies a contradiction than the proposition that it will rise. Thought alone is therefore, never sufficient to assure us of the truth of any matter of fact. Sense experience is needed. Only what is directly present to the senses at a given moment is known by perception. A belief in a matter of fact which is not present at the time must therefore be arrived at by a transition of some kind from present impressions to a belief in the matter of fact in question. Hume’s theory of knowledge is primarily an explanation of how that transition is in fact made. It takes the form of an empirical ‘science of human nature’ which is to be based of careful observation of what human beings do and what happens to them.
 Its leading into some tangible value, which approves inversely qualifying, in that thoughts have contents carried by mental representations. Now, there are different representations, pictures, maps, models, and words - to name only some. Exactly what sort of representation is mental representation? Insofar as our understanding of cognizant connectionism will necessarily have implications for philosophy of mind. Two areas in particular on which it is likely to have impact are the analysis of the mind as a representational system and the analysis of intentional idioms. That is more that imagery has played an enormously important role in philosophy conceptions of the mind. The most popular view of images prior to this century has been what we might call ‘the picture theory’. According to this view, held by such diverse philosophers as Aristotle, Descartes, and Locke, mental images - specifically in the way they represent objects in the world,. Despite its widespread acceptance, the picture theory of mental images was left largely unexplained in the traditional philosophical literature. Admittedly, most of those accepted the theory held that mental images copy or resemble what the present, but little more was said. Sensationalism, distinguishes itself as a version of representationalist by positing that mental representations are themselves linguistic expressions within a ‘language of thought’. While some sententialists conjecture that the language of thought is just the thinker’s spoken language internalized. An unarticulated, internal; language in which the computations supposedly definitive of cognition occur. Sententialism is as a natural consequence to take hold a provocative thesis.
 Thoughts, in having contents, posses semantic properties, yet, that does not imply that they lack an unspoken, internal, mental language. Sententialism need not insist that the language of thought be any natural spoken language like Chinese or English. Rather it simply proses that psychological states that admit of the sort of semantic properties are likely relations to the sort of structured representations commonly found in, but not isolated to, public languages. This is certainly not to say that all psychological states in all sorts of psychological agents must be relations to mental sentences. Rather the idea is that thinking - at least, the kind Peter Abelard (1079-1142) exemplifies - involves the processing of internally complex representations. Their semantic properties are sentences to those of their parts much in the manner in which the meanings and truth conditions of complex public sentences are dependent upon the semantic features of their components. Abelard might also exploit various kinds of mental representations and associated processes. A sententialists may allow that in some of his cognitive adventures Abelard rotates mental images or recalcitrates weights on connections among internally undifferentiated networked nodes. Sententialism is simply the thesis that some kinds of cognitive phenomena are best explained by the hypothesis of a mental language. There is, then, no principled reason of non-verbal creatures precludes the language of thought.
 It is tempting too sleek over the representational theory by speaking of a language thought, nonetheless, that Fodor argues that representation and the inferential manipulation of representations require a medium of representation, least of mention, in human subjects than in computers.  Say, that physically realized thoughts and mental representations are ‘linguistic’, such that of (1) they are composed of parts and are syntactically structured: (2) Their simplest parts refer to or denote things and properties in the world, (3) their meanings as wholes are determined by the semantical properties of their basic parts together with the grammatical rules that have generated their overall syntactic structures, (4) they have truth-conditions, that is, putative states of affairs in the world that would make them true, and accordingly they are true or false depending on the way the world happens actually to be: (5) They bear logical relations of entailment or implication to each other.  In this way, they have according to the representational theory: Human beings have systems of physical states that serve as the elements of a lexicon or vocabulary, and human beings (somehow) physically realize rules that combine strings of those elements into configuration having the plexuities of representational contents that common sense associates with the propositional altitudes. And that is why thoughts and beliefs are true or false just as English sentences are, though a ‘language of thought’ may differ sharply in its grammar from any natural language.
 Thought and language, in philosophy are evidently importantly related, but how exactly are they related? Does language come first and make thought possible or vice versa? Or are they on a par, each making the other possible?
 When the question is stated this generally, has nonetheless no unqualified answer is possible. In some respects language is prior, in other respects thought is prior. For example, it is arguable that a language is an abstract pairing of expressions and meanings, a function, in the set-theoretic sense, from expressions onto meanings. This makes sense of the fact that Esperanto is a language no one speaks, and it explains why it is that, while it is a contingent fact that, ‘snow is white’, it is a necessary truth that it means that snow is white. However, if natural languages such as French and English are abstract objects in this sense, then they exist whether or not anyone speaks them: They even exist in possible worlds in which there are no thinkers. Once, again, language, as well as such notions as meaning and truth in a language, is prior to thought.
 Yet, even if languages are construed as abstract expression-meaning pairings, they are construed that way as abstractions from actual linguistic practice - from the use of language in communicative behaviour - and there remains a clear sense in which language is dependent on thought. The sequence of succession is that, ‘Naples is south of Rome’ mans among us that Naples is south of Rome. This is a contingent fact, dependent on the way we use ‘Naples’, ‘Rome’ and the other parts of that sentence. Had our linguistic practices been different, ‘Naples is south of Rome’ might have meant something entirely different or nothing at all among us. Plainly, the fact that ‘Naples is south of Rome’ means among us that Naples is south of Rome has something to do with the ‘beliefs’ and ‘intentions’ underlying our use of the words and structure that compose the sentence. More generally, it is a platitude that the semantic features that decide on or upon the mark and sounds have in population of speakers ate, at least, partly determined by the propositional altitudes, those speakers have in using those marks and sounds, or in using the parts and structure that compose them. This is the same platitude, of course, which says that meaning depends at least partly on use: For the use in question is intentional use in communicative behaviour. So here is one clear sense in which is required to imbue marks and sounds with the semantic features they have in populations of speakers.
 We know that there is some relation R such that a language L is used by a population P iff L bears R to P. This relation, however, of whatever it turns out to be, the actual-language relation is to explain the semantic features expressions, least of mention, have among those who are apt to produce those expressions, and we know that any account of the relation must require language users to have certain propositional attitudes. But how exactly is the actual-language relation to be explained in terms of the propositional attitudes of language users? And what sort of dependence might those propositional attitudes in turn have on language or on the semantic features that are fixed by the actual-language relation?
 Some philosophers object to intention-based semantics only because they think it precludes a dependence of thought on the communicative use of language. This is a mistake. Even if intention-based semantic definitions are given a strong reductionist reading, as saying that public-language semantic properties (i.e., those semantic properties that supervene on us in communicative behaviour) just are psychological properties. It might still be that one could not have propositional attitudes unless one had mastery of a public language. The idea of supervenience is usually thought to have originated in moral theory, in the works of such philosopher s as G.E. Moore and R.M. Hare, nonetheless, Hare, for example, claimed that ethical predicates are ‘supervenient predicates’ in the same sense that no two things (persons, acts, states of affairs) could be exactly alike in all descriptive or naturalistic respects but unlike in that some ethical predicate (‘good’, right’, etc.) truly applies to one but not to the other. That is, there could be no difference in a moral respect without a difference in some description, or non-moral respect. following Moore and Hare, from whom he avowedly borrowed the idea of supervenience, Davidson went on to assert that supervenience in the sense is consistent with the irreducibility of the supervenient to their ‘subvenient’, or ‘base’, properties. ‘Dependence or supervenience of this kind does not entail reducibility through law or definition  . . . ’.
 Thus, three ideas have come to be closely associated with supervenience: (1) ‘Property covariation’ (if two things are indiscernible in base properties, they must be indiscernible in supervenience properties). (2) ‘Dependence’ (supervenient properties are dependent on, or determined by, their subvenient bases, and (3) ‘Non-reducibility’ (property covariation and dependence involved in supervenience can not reducible to their base properties). Whether or not this is plausible (that is, a separate question), it would be no more logically puzzling that the idea that one could not have propositional attitudes unless one had ones with certain sorts of content, Tyler Burge’s insight, that the contents of one’s thoughts is partially determined by the meaning of one’s words on one’s linguistic community is perfectly consistent with any intention-based semantics, reduction of the semantic to the psychological. Nevertheless, there is reason to be sceptical of the intention-based semantic programme.
 So the most reasonable view about the actual-language relation is that it requires language users to have certain propositional attitudes, but there is no prospect of defining the relation wholly in terms of non-semantic propositional attitudes. It is further plausible that any account of the actual-language relation ,must appeal to speech acts such as speaker meaning, where the correct account of these speech acts is irreducibly semantic (they will fail to supervene on the non-semantic propositional attitudes of speakers in the way that intentions fail to supervene on an agent’s beliefs and desires). Is it possible to define the actual-language relation, and if so, will any irreducibly semantic notions enter into that definition other than the sorts of speech act notions already alluded to? These questions have not been much discussed in the literature, there is neither an established answer nor competing schools of thought. However, the actual-language relation is one of the few things in philosophy that can be defined, and that speech act notions are the only irreducibly semantic notions the definition must appeal to (Schiffer, 1993).
 An substantiated dependence of thought on language seems unobtainably approachable, however, a useful point is an acclaimed dependence that propositional attitudes are relations to linguistic items which obtain, in, at least, in part, by virtue of the content those items have among language users. This position does not imply that believers have to be language users, but it does make language an essential ingredient in the concept of belief. The position is motivated by two considerations: (a) The supposition that believing is a relation to thing believed, which things have truth values and stand in logical relations to one another, and (b) the desire not to take things believed to be propositions - abstract, mind and language-independent objects that have essentially the truth conditions they have. As to say that (as well motivated: The relational construal of propositional attitudes is probably the best way to account for the quantification in ‘Harvey believes something irregular about you’. But there are problems with taking linguistic items, than propositions, as the objects of belief. In that, if ‘Harvey believes that irregularities are founded grounds held to abnormality’ is represented along the lines of Harvey, and abnormal associations founded to irregularity, then one could know the truth expressed by the sentence about Harvey without knowing the content of his belief: For one could know that he stands in the belief relation to ‘irregularities are abnormal’ without knowing its content. This is unacceptable, as if Harvey believes that irregularity stems from  abnormality, then what he believes - the reference of ‘That irregularity is abnormal’ - is that irregularities are abnormal. But what is this thing, which irregularities are abnormal? Well, it is abstract, in that it has no spatial locality: It is mind and language independent, in that it exists in possible world in which whose displacement is neither the thinkers nor speakers, and necessarily, it is true iff irregularly is abnormal. In short, it is a proposition - an abstract mind and-language thing that has a truth condition and has essentially the truth condition it has.
 A more plausible way that thought depends on language is suggested by the topical thesis that we think in a ‘language of thought’. As, perhaps, this is nothing more than the vague idea that the neural states that realize our thoughts ‘have elements and structure in a way that is analogous to the way in which sentences have elements and structure’. But we can get a more literal rendering by relating it to the abstractive conception of language  already recommended. On this conception, a language is a function from ‘expressions’ - sequence of marks or sounds or neural states or whatever - onto meanings, which meanings will include the propositions our propositional-attitude relations relates us to. We could then read the language of thought hypothesis as the claim that having in a certain relation to a language whose expressions are neural states. There would mow be more than one ‘actual-language relation’. One might be called the ’public-language relation’, since it makes a language the instrument of communication of a population of speakers. Another relation might be called the ‘language-of-thought relation’ because standing in the relation to a language makes it one’s ‘Lingus mentis’. Since the abstract notion of a language has been so weakly construed, it is hard to see how the minimal language-of-thought proposal just sketched could fail to be true. At the same time, it has been given no interesting work to do. In trying to give it more interesting work, further dependencies of thought on language might come into play. For example, it has been claimed that the language of thought of a public-language user is the public language she uses: her neural sentences in something like her spoken sentences. For another example, it might be claimed that even if one’s language of thought is distinct from one’s public language, the language-of-thought relation makes presuppositions about the public-language relation in ways that make the content of one’s thoughts dependent on the meaning of one’s words in one’s public-language community.
 Tyler Burge has in fact shown that there is as sense in which thought content is dependent on the meaning of words in one’s linguistic community (Burge, 1979). Alfred, for instance, uses ‘arthritis’ under the misconception that arthritis is not confined to the joints, he also applies the word to rheumatoid ailments not in the joints. Noticing an ailment in his thigh that is symptomatically like the disease in his hands and ankles, he says to his doctor, ‘I have arthritis in the thigh’. Here Alfred is expressing his false belief that he has arthritis in the thigh. But now consider a counterfactual situation that differs in just one respect (and whatever it entails): Alfred would be expressing a true belief when he says ‘I have arthritis in the thigh’. Since the proposition he believes is true while the proposition that he has arthritis in the thigh is false, he believe’s some other proposition. This shows that standing in the belief relation to a proposition can be partly determined by the meaning of words in one’s public language. The Burge phenomenon seem real, but it would be nice to have a deep explanation of why thought content should be dependent on language in this way.
 Finally, there is the old question of whether, or to what extent, a creature who does not understand a natural language can have thoughts. Now it seems pretty compelling that higher mammals and humans raised without language have their behaviour controlled by mental states that are sufficiently like our beliefs, desires and intentions to share those labels. It also seems easy to imagine non-communicating creatures who have sophisticated mental lives (they build weapons, dams, bridges, have clever hunting devices, etc.) At the same time, ascriptions of particular contents to non-language-using creatures typically seem exercises in loose speaking (does the dog really believe that there is a bone in the yard?), and it is no accident that, as a ,matter of fact, creatures who do not understand a natural language have at best, primitive mental lives. There is no accepted explanation of these facts. It is possible that the primitive mental lives of animals account for their failure to master natural language, but the better explanation may be Chomsky’s, that animals lack a special language faculty unique to our species. As regards the inevitable primitive mental life of an otherwise language, this might simply be due to the ignorance and lack of intellectual stimulation such a person would be doomed to. As such, it might require a neural language with a structure comparable to that of a natural language, and that such neural languages are somewhat acquire, as the child learns its native language. Finally, the ascription of content to the propositional attitudes states of language creatures is a difficult topic that needs more attention. It is possible that we as we learn more about the logic of our ascriptions of propositional content, we will realize that these ascriptions are egocentrically based on a similarity to the language in which we express our beliefs. We might then learn that we have no principled basis for ascribing propositional content to a creature who does not speak languages, or who does not have internal states with natural-language-like structure. It is somewhat surprising how little we know about thoughts’s dependence on language.
 All of this suggests a specific ‘mental organ’, to use Chomsky’s phrase, that has evolved in the human cognitive system specifically in order to make language possible. The specific structure of this organ simultaneously constrains the range of possible human languages and guides the learning of the child’s target language, later ,making rapid on-line language processing possible. The principles represented in this organ constitute the innate linguistic knowledge of the human being. Additional evidence for the early operation of such an innate language acquisition module is derived from the many infant studies that show that infants selectively attend to sound-streams that are prosodically appropriate that have pauses at clausal boundaries, and that contain linguistically permissible phonological sequences.
 A particularly strong form of the innateness hypothesis in the psycholinguistic domain is Fodor’s (1975, 1987), ‘Language of Thought’ hypothesis. Fodor argues not only that the language learning and processing faculty is innate, but that the human representational system exploits an innate language of thought which has all of the expressive power of any learnable human language. Hence, he argues, all concepts are in fact innate, in virtue of the representational power of the language of thought. This remarkable doctrine is hence even stronger than classical rationalist doctrine of innate ideas: Whereas, Chomsky echoes Descartes in arguing that the most general concepts required for language learning are innate, while allowing that more specific concepts are acquired, Fodor echoes Plato in arguing that every concept we ever ‘learn’ is in fact innate.
 Fodor defends this view by arguing that the process of language learning is a process of hypothesis formation and testing, where among the hypotheses that must be formulated are meaning postulates for each term in the language being acquired. But in order to formulate and test a hypothesis of the form ‘χ’ means ‘y’, where ‘χ’ denotes a term in the target language, prior to the acquisition of that language, the language learner. Fodor argues, must have the resources necessary to express ‘y’. Therefore, there must be, in the language of thought, a predicate available co-extensive with each predicate in any language that a human can learn. Fodor also argues for the language of thought thesis by noting that the language in which the human information cannot be a human spoken language, since that would, contrary to fact, privilege one of the world’s languages as the most easily acquired. Moreover, it cannot be, he argues, that each of us thinks in our own native language since that would (a) predict that we could not think prior to acquiring a language, contrary to the original argument, and (b) would mean that psychology would be radically different for speakers of different languages. Hence, Fodor argues, there must be a non-conventional language of thought, and the facts that the mind is ‘wired’ in mastery of its predicates together with its expressive completeness entail that all concepts are innate.
 The dissertating disputation about whether there are innate qualities that infer on or upon the innate values whereby ideas are much older than previously imagined. Plato  in the ‘Meno’ (the learning paradox), famously argues that all of our knowledge is innate. Descartes (1596-1650) and Leibniz (1646-1716) defended the view that the mind contains innate ideas: Berkeley (1685-1753), Hume (1711-76) and Locke (1632-1704) attacked it. In fact, as we now conceive the great debate between European Rationalism and British empiricism in the seventeenth and eighteenth centuries, the doctrine of innate ideas is a central effectuality of contention: Rationalists typically claim that knowledge is impossible without a significant stock of general innate ‘concepts’ or judgements, empiricists argued that all ideas are acquired from experience. This debate is replayed with more empirical content and with considerably greater conceptual complexities in contemporary cognitive science, most particularly within the domain of psycholinguistic theory and cognitive developmental theory. Although Chomsky is recognized as one of the main forces in the overthrow of behaviourism and in the initiation of the ‘cognitive era’. His relation between psycholinguistics and cognitive psychology has always been an uneasy one. The term ‘psycholinguistics’ is often taken to refer primarily to psychological work on language that is influenced by ideas from linguistic theory. Mainstream cognitive psychologists, for example when they write textbooks, oftentimes prefer the term ‘psychology of language’ the difference is not, however, merely in a name, least be of mention, that both Fodor and Chomsky, who argue that all concepts, or all of linguistic knowledge is innate, lend themselves to this interpretation, against empiricists who argue that there is no innate appeal in explaining the acquisition of language or the facts of cognitive development. But this debate would be a silly and a sterile for obvious reasons, something is innate. Brains are innate, and the structure of the brain must constrain the nature of cognitive and linguistic development to dome degree. Equally obviously, something is learned and is learned as opposed too merely grown as limbs or hair grow. For not all of the world’s citizens end up speaking English, or knowing the Special Theory of Relativity. The interesting questions then all concern exactly what is innate, to what degree it counts as knowledge, and what is learned, and what degree its content and structure are determined by innately specified cognitive structures. And that is plenty to debate about.
 Innatist argue that the very presence of linguistic universals argue for the innateness of linguistic knowledge, but more importantly and more compelling that the fact that these universals are, from the standpoint of communicative efficiency, or from the standpoint of any plausible simplicity criterion, adventitious. There are many conceivable grammars, and those determined by universal grammar are not ipso facto the most efficient or the simplest. Nonetheless, all human language satisfy the constraints of universal grammar. Since neither the communicative environment nor the commutative task can explain this phenomenon. It is reasonable to suppose that it is explained by the structure of the mind - and, therefore, by fact that the principles of universal grammar lie innate in the mind and constrain the language that a human can acquire.
 Linguistic empiricists, answer that there are alternative possible explanations of the existence of such adventitious universal properties of human languages. For one thing, such universals could be explained, Putnam (1975, 1992) argues, by appeal to a common ancestral language, and the inheritance of features of that language by its descendants. Or it might turn out that despite the lack of direct evidence at present the features of universal grammar in fact do serve either the goals of communicative efficacy or simplicity according to a metric of psychological importance. Finally, empiricist point out , he very existence of universal grammar might be a trivial logical artefact (Quine, 1968): for one thing, any finite set of structures will have some feature s in common. Since there are a finite number of languages, it follows trivially that there are features they all share. Moreover, it is argued, many features of universal grammar are interdependent. So in fact the set of functional principles shared by the world’s languages may be rather small. Hence, even if these are innately determined, the amount of innate knowledge thereby required may be quite small as compared with the total corpus of general linguistic knowledge acquired by the first language learner.
 These replies are rendered less plausible, innatists argue, when one considers the fact that the errors language learners make in acquiring their first language seem to be driven far more by abstract features of grammar than by any available input data. So, despite receiving correct examples of irregular plurals or past tense forms for verbs, and despite having correctly formed the irregular forms for those words, children will often incorrectly regularize irregular verbs once acquiring mastery of the rule governing regulars in their language. And in general, not only the correct inductions of linguistic rules by young language learners, but more importantly, given the absence of confirmatory data and the presence of refuting data, children’s erroneous inductions are always consistent with universal grammar, often simply representing the incorrect setting of a parameter in the grammar. More generally, innatists argue, that all grammatical rules that have ever been observed satisfy the structure-dependence constraint. That is, many linguists and psycholinguists argue that all known grammatical rules of all the world’s languages, including the fragmentary languages of young children must be stated as rules governing hierarchical sentence structures, and not governing, say, sequence of words. Many of these, such as the constituent-command constraint governing anaphor, are highly abstract indeed, and appear to be respected by even very young children (Solan, 1983 & Crain, 1991). Such constraints may, innatists argue, be necessary conditions of learning natural language I the absence of specific instruction, modelling and correction conditions in which all first language learning acquire their native languages.
 An important empiricist answer for these observations derives from recent studies of ‘connectionist’ models of the first language acquisition (Rummelhart & McClelland, 1986, 1987). Connectionist systems, not previously trained to represent any sunset of universal grammar that induce grammar which include a large set of regular forms and a few irregulars also tend to over-regularize, exhibiting the same U-shape learning curve seen in human language acquirers. It is also noteworthy that conceptionist learning systems that induce grammatical systems acquire ‘accidentally’ rules on which they are not explicitly trained, but which are consistent with those upon which they are trained, suggesting that s children acquire position of their grammar, they may accidentally ‘learn’ other consistent rules, which may be correct in other human language, but which then must be ‘unlearned’ in their home language. Yet, such ‘empiricist’ language acquisition systems have yet to demonstrate their ability to induce a sufficiently wide range of the rules hypothesized to be comprised by universal grammar to constitute a definite empirical argument for the possibility of natural language acquisition in the absence of a powerful set of innate constraints.
 The poverty of the stimulus argument has been of enormous influence in innateness debates, though its soundness is hotly contested. Chomsky notes that (1) the examples of the target language to which the language learner is exposed are always jointly compatible with an infinite number of alternative grammars, and so vastly undermine the grammar, of the language, and (2) the corpus always contains many examples of ungrammatical sentences, which should in fact, serve as falsifiers of any empirically induced correct grammar of the language, also (3) there is, in general, no explicit reinforcement of correct utterances or correction of incorrect utterances, either by the learner or by those in the immediate training environment. Therefore, he argues, since it is impossible to explain the learning of the correct grammar - a task accomplished by all normal children within a very few years - on the basis of any available data or known learning algorithms, it must be that the grammar is innately specified, and is merely ‘triggered’ by relevant environmental cues.
 Opponents of the linguistic innateness hypothesis, however, point out that the circumstance that Chomsky notes in this argument is hardly specific to language. As well known from arguments due to Hume (1978). Wittgenstein (1953), Goodman (1972) and Kripke (1982), in all cases of empirical abduction, and of training in the use of a word, data under-determine theories. This moral is emphasized by Quine (1954, 1960) as the principle of the undertermination of theory by data. But we, nonetheless, do abduce adequate theories in science, and we do lean the meaning of words. And it would be bizarre to suggest that all correct scientific theories or the facts of lexical semantics are innate.
 But, innatists reply, that when the empiricist relies on the underdetermination of theory by data as a counterexample, a significant disanalogousness with language acquisition is ignored: The abduction of scientific theories is a difficult, labourious process, taking a sophisticated theorist a great deal of time and deliberate effort. First language acquisition, by contrast, is accomplished effortlessly and very quickly by a small child. The enormous relative ease with which such a complex and abstractive domain is mastered by such a naïve ‘theorist’ is evidence for the innateness of the knowledge achieved.
 Empiricists such as Putnam (1926- ) have rejoined that innateness under-estimate the amount of time that language learning actually takes, focussing only on the number of years from the apparent onset of acquisition to the achievement of relative mastery over the grammar. Instead of noting how short this interval, they argue, one should count the total number of hours spent listening to language and speaking during this time. That number is in fact, quite large, and is comparable to the number of hours of study and practice required in the acquisition of skills that are not argued to derive from innate structures, such as chess playing or musical composition, hence, they argue once the correct temporal parameters are taken into consideration, language learning looks like one more case of human skill acquisition than like a special unfolding of innate knowledge.
 Innatists, however, note that while the ease with which most such skills are acquired depends on general intelligence, language, is learned with roughly equal speed, and too roughly the same level of general syntactic mastery regardless of general intelligence. In fact, even significantly retarded individuals, assuming no special language deficit, acquire their native language on a time-scale and to a degree comparable to that of normally intelligent children. The language acquisition faculty hence, appears to allow access to a sophisticated body of knowledge independent of the sophistication of the general knowledge of the language learner. This is, language learning and utilization mechanisms are not outside of language processing. They are informationally encapsulated - only linguistic information is relevant to language acquisition and processing. They are mandatory - language learning and language processing are automatic. Moreover, language is subserved by specific dedicated neural structures, damage to which predictably and systematically impairs linguistic functioning, and not general cognitive functioning.
 Again, the issues at stake in the debate concerning the innateness of such general concepts pertaining to the physical world cannot be s stark a dispute between an innate and one according to which all empirical knowledge is innate. Rather the important - and again, always empirical questions concern just what is innate, and just ‘what’ is acquired, and how innate equipment interacts with the world to produce experience. ‘There can be no doubt that all our knowledge begins with experience . . . experience it does not follow that all arises out of experience’.
 Philosophically, the unconscious mind postulated by psychoanalysis is controversial, since it requires thinking in terms of a partitioned mind and applying a mental vocabulary (intentions, desires, repression) to a part to which we have no conscious access. The problem is whether this merely uses a harmless spatial metaphor of the mind, or whether it involves a philosophical misunderstanding of mental ascription. Other philosophical reservations about psychoanalysis concern the apparently arbitrary and unfalsifiable nature on the interpretative schemes employed. Basically, least of mention, the method of psychoanalysis  or psychoanalytic therapy for psychological disorders was  pioneered by Sigmund Freud (1856-1939), the method relies on or upon an interpretation of what a patient says while ‘freely associating’ or reporting what comes to mind in connection with topics suggested by the analyst. The interpretation proceeds according to the scheme favoured by the analyst, and reveals ideas dominating the unconscious, but previously inadmissible to the conscious mind of the subject. When these are confronted, improvement can be expected. The widespread practice of psychoanalysis is not matched by established data on such rate of improvement.
 Nonetheless, the task of analysing psychoanalytic explanation is complicated is initially in several ways. One concerns the relation of theory to practice. There are various perspectives on the relation of psychoanalysis, the therapeutic practice, to the theoretical apparatus built around it, and these lead to different views of psychoanalysis’ claim to cognitive status. The second concerns psychoanalysis’ legitimation.  The way that psychoanalytic explanation is understood has immediate implications for one’s view of its truth or acceptability, and this of course a notoriously controversial matter. The third is exegetical. Any philosophical; account of psychoanalysis must of course start with Freud himself, but it will inevitably privilege some strands of his thought at the expense of others, and in so doing favour particular post-Freudian developments over others.
 Freud clearly regarded psychoanalysis as engaged principally in the task of explanation, and held fast to his claims for its truth in the course of alterations in his view of the efficacy of psychoanalysis’ advocates have, under pressure, retreated to the view that psychoanalytic theory has merely instrumental value, as facilitating psychoanalytic therapy: But this is not the natural view, which is that explanation is the autonomous goal of psychoanalysis, and that its propositions are truth-evaluable. Accordingly, it seems that preference should be given to whatever reconstruction of psychoanalytic theory does most to advance its claim to truth. Within, of course, exegetical constraints (what a reconstruction offers must be visibly present in Freud’s writings.)
 Viewed in these terms, psychoanalytic explanation is an ‘extension’ of ordinary psychology, one that is warranted by demands for explanation generated from within ordinary psychology itself. This has several crucial ramifications. It eliminates, as ill-conceived, the question of psychoanalysis’ scientific status - an issue much discussed, as proponents of different philosophies of science have argued for and against psychoanalysis’ agreement with the canons of scientific method, and its degree or lack of correspondence. Demands that psychoanalytic explanation should be demonstrated to receive inductive support, commit itself to testable psychological laws, and contribute effectively to the prediction of action, have then no more pertinence than the same demands pressed on ordinary psychology - which is not very great. When the conditions for legitimacy are appropriately scaled down. It is extremely likely that psychoanalysis succeeds in meeting hem: For psychoanalysis does deepen our understanding of psychological laws, improve the predictability of action in principle, and receive inductive support on the special sense which is appropriate to interpretative practices.
 Furthermore, to the extent that psychoanalysis may be seen as structured by and serving well-defined needs for explanation, there is proportionately diminished reason for thinking that its legitimation turns on the analysand’s assent to psychoanalytic interpretation, or the transformative power (whatever it may be) of these. Certainly it is true that psychoanalytic explanation has a reflective dimension lacked by explanations in the physical sciences: Psychoanalysis understands its object, the mind, in the very terms that the mind employs in its unconscious workings (such as its belief in its own omnipotence). But this point does not in any way count against the objectivity of psychoanalytic explanation. It does not imply that what it is for a psychoanalytic explanation to be true should be identified, pragmatically, with the fact that an interpretation may, for the analysand who gains self-knowledge, have the function of translating their directed-causes to set about unconscious mentality into a proper conceptual form. Nor does it imply that psychoanalysis’ attribution of unconscious content needs to be understood in anything less than full-bloodedly realistic terms. =truth in psychoanalysis may be taken to consist in correspondence with an independent mental reality, a reality that is both endorsed with ‘subjectivity’ and in many respects puzzling to its owner.