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 To speak of sensations of red objects, tubas and so forth, is to say that these sensations carry information about an object’s colour, its shape, orientation, and position and (in the case of audition) information about acoustic qualities such as pitch, timbre, volume. It is not to say that the sensations share the properties of the objects they are sensations of or that they have the properties they carry information about. Auditory sensations are not loud and visual sensations are not coloured. Sensations are bearers of nonconceptualized information, and the bearer of the information that something is red need not itself be red. It need not even be the sort of thing that could be red: It might be a certain pattern of neuronal events in the brain. Nonetheless, the sensation, though not itself red, will (being the normal bearer of the information) typically produce in the subject who undergoes the experience a belief, or tendency to believe, that something red is being experienced. Hence the existence of hallucinations.
 Just as there are theories of the mind that would deny the existence of any state of mind whose essence was purely qualitative (i.e., did not consists of the state’s extrinsic, causal, properties) there are theories of perception and knowledge ~ cognitive theories ~ that denies a sensory component to ordinary sense perception. The sensor y dimension (the look, feel, smell, taste of things) is (if it is not altogether denied) identified with some cognitive condition (knowledge or belief) of the experienced. All seeing (not to mention hearing, smelling and feeling) becomes a form of believing or knowing. As a result, organisms that cannot know cannot have experiences. Often, to avoid these striking counterintuitive results, implicit or otherwise unobtrusive (and, typically, undetectable) forms of believing or, knowing.
 Aside, though, from introspective evidence (closing and opening one’s eyes, if it changes beliefs at all, doesn’t just change beliefs, it eliminates and restores a distinctive kind of conscionable experience), there is a variety of empirical evidence for the existence of a stage in perceptual processing that is conscious without being cognitive (in any recognizable sense). For example, experiments with brief visual displays reveal that when subjects are exposed for very brief (50 msec.) Intervals to information-rich stimuli, there is persistence (at the conscious level) of what is called an image or visual icon that embodies more information about the stimulus than the subject can cognitively process or report on. Subjects cab exploit the information in this persisting icon by reporting on any part of the absent array of numbers (the y can, for instance, reports of the top three numbers, the middle three or the bottom three). They cannot, however, identify all nine numbers. The y report seeing all nine, and the y can identify any one of the nine, but they cannot identify all nine. Knowledge and brief, recognition and identification ~ these cognitive states, though present for any two or three numbers in the array, are absent for all nine numbers in the array. Yet, the image carries information about all nine numbers (how else accounts for subjects’ ability to identify any number in the absent array?) Obviously, then, information is there, in the experience itself, whether or not it is, or even can be. As psychologists conclude, there is a limit on the information processing capacities of the latter (cognitive) mechanisms that are not shared by the sensory stages themselves.
 Perceptual knowledge is knowledge acquired by or through the senses. This includes most of what we know. Some would say it includes everything 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 ~ that the light has turned green ~ by use of the eyes. Feeling that the melon is overripe in coming to know a fact ~ that the melon is overripe ~ by one’s sense of 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.
 Seeing a rotten kumquat is not at all like the experience of smelling, tasting or feeling a rotten kumquat. Yet all these experiences can result in the same knowledge ~ Knowledge that the kumquat is rotten. Although the experiences are much different, they must, if they are to yield knowledge, embody information about the kumquat: The information that it is rotten. Seeing that the fruit is rotten differs from smelling that it is rotten, not in what is known, but how it is known. In each case, the information has the same source ~ the rotten kumquat -, but it is, so top speak, delivered via different channels and coded and re-coded in different experiential neuronal excitations as stimulated sense attractions.
 It is important to avoid confusing perceptual knowledge of facts, e.g., that the kumquat is rotten, with the perception of objects, e.g., rotten kumquats. It is one thing to see (taste, smell, feel) a rotten kumquat, and quite another to know (by seeing or tasting) that it is a rotten kumquat. Some people, after all, don not know what kumquats look like. They see a kumquat but do not realize (do mot see that) it is a kumquat. Again, some people do not know what a kumquat smell like. They smell a rotten kumquat and ~ thinking, perhaps, that this is a way this strange fruit is supposed to smell ~ does not realize from the smell, i.e., do not smell that it is a rotted kumquat. In such cases people see and smell rotten kumquats ~ and in this sense perceive rotten kumquat ~ and never know that they are kumquats ~ let alone rotten kumquats. They cannot, not at least by seeing and smelling, and not until they have learned something about (rotten) kumquats. Since the topic as such is incorporated in the perceptual knowledge ~ knowing, by sensory means, that something if ‘F’ -, we will be primary concerned with the question of what more, beyond the perception of F’s, is needed to see that (and thereby know that) they are ‘F’. The question is, however, not how we see kumquats (for even the ignorant can do this) but, how we know (if, that in itself, that we do) that, that is what we see.
 Much of our perceptual knowledge is indirect, dependent or derived. By this is that it is  meant 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 fat, in a more direct way. We see, by the gauge, that we need gas, see, by the newspapers, that our team has lost again, or see, by her expression that is nervous. This derived or dependent sort of obtainable knowledge is particularly prevalent in the case of vision but it occurs, to a lesser degree, in every sense modality. We install bells and other noise-makers so that we can, for example, hear (by the bells) that someone is at the door and (by the alarm) that its time to get away. When we obtain knowledge in this way. It is clear that unless one sees ~ hence, comes to know. Something about the gauge (that it reads ‘empty’), the newspaper (which is says) and the person’s expression, one would not see (hence, know) what one is described as coming to know by perceptual means. If one cannot hear that the bell is ringing, one cannot ~ not 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, or dependent on, the more basic perceptual knowledge that ‘b’ is ‘G’.
 Though perceptual knowledge about objects is often, in this way, dependent on knowledge of fats about different objects, the derived knowledge is sometimes about the same object. That is, we see that ‘a’ is ‘F’ by seeing, not that some other object is ‘G’, but that ‘a’ itself is ‘G’. We see, by her expression, that she is nervous. She tells that the fabric is silk (not polyester) by the characteristic ‘greasy’ feel of the fabric itself (not, as I do, by what is printed on the label). We tell whether it is an oak tree, a Porsche, a geranium, an igneous rock or a misprint by its shape, colour, texture, size, behaviour and distinctive markings. Perceptual knowledge of this sort is also deprived ~ derived from the more basic facts (about ‘a’) we use to make the identification. In this case the perceptual knowledge is still indirect because, although the same object is involved, the facts we come to know about it are different from the facts that enable us to know it.
 Derived knowledge is sometimes described as inferential, but this is misleading, at the conscious level there is no passage of the mind from premise to conclusion, no reasoning, no problem-solving. The observer, the one who sees that ‘a’ is ‘F’ by seeing that ‘b’ (or ‘a’ itself) is ‘G’, need not be (and typically is not) aware of any process of inference, any passage of the mind from one belief to another. The resulting knowledge, though logically derivative, is psychologically immediate. I could see that she was getting angry: so, I moved my hand. I did not, ~ at least not at any conscious level ~ infers (from her expression and behaviour) that she was getting angry. I could (or, so it seemed to me) see that she was getting angry. It is this psychological immediacy that makes indirect perceptual knowledge a species of perceptual knowledge.
 The psychological immediacy that characterises so much of our perceptual knowledge ~ even (sometimes) the most indirect and derived forms of it ~ does not mean that learning is not required to know in this way. One is not born with (may, in fact, never develop) the ability to recognize daffodils, muskrats and angry companions. It is only after a long experience that one is able visually to identify such things. Beginners may do something corresponding to inference: They recognize relevant features of trees, birds, and flowers, factures they already know how to perceptually identify, and then infer (conclude), on the basis of what they see, and under the guidance of more expert observers, that its an oak a finch or a geranium. But the experts (and we are all experts on many aspects of our familiar surroundings) do not typically go through such a process. The expert just sees that its an oak, a finch or a geranium. The perceptual knowledge of the expert is still dependent, of course, since even an expert cannot see what kind of flower it is if she cannot first see its colour and shape, but it is to say, that the expert has developed identificatory skills that no longer require the sort of conscious inferential process that characterize a beginner’s efforts.
 Coming to know that ‘a’ is ‘F’ by seeing that ‘b’ is ‘G’ obviously requires some background assumption on the part of the observer, an assumption to the effect that ‘a’ is ‘F’ (or perhaps only probable ‘F’) when ‘b’ is ‘G’. If one does not assume (as taken to be granted) that the gauge is properly connected, and does not, thereby assume that it would not register ‘empty’,unless the tank was nearly empty, then even if one could see that it registered ‘empty’, one would not learn ( hence, would not see) that one needed gas. At least, one would not see it by consulting the gauge. Likewise, in trying to identify birds, its no use being able to see their markings if one doesn’t know something about which birds have which marks ~ sometimes of the form: A bird with these markings is (probably) a finch.
 It would seem, moreover, that these background assumptions, if they are to yield knowledge that ‘a’ is ‘F’, as they must if the observer is to see (by b’s being ‘G’) that ‘a’ is ‘F’, must themselves qualify as knowledge. For if this background fact is not known, if it is not known whether ‘a’ is ‘F’ when ‘b’ is ‘G’, then the knowledge of b’s being ‘G’, taken by itself, powerless to generate the knowledge that ‘a; is ‘F?’. If the conclusion is to be known to be true, both the premises used to reach that conclusion must be known to be true. Or so it would seem.
 Externalism/Internalism are most generally accepted of this distinction if that a theory of justification is internalist, if and only if it requires that all of the factors needed for a belief to be epistemically justified for a given person be cognitively accessible to that person. Internal to his cognitive perspective, and external, if it allows that, at least, part of the justifying factor need not be thus accessible, so they can be external to the believers’ cognitive perspective, beyond his understanding. As complex issues well beyond our perception to the knowledge or an understanding, however, epistemologists often use the distinction between internalist and externalist theories of epistemic justification without offering any very explicit explication.
 The externalism/internalism 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 content.
 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 be 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.
 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 its 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 ~ either 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 believes. 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 means 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 is 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 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 abound in. 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 entities posited by the relevant discourse exist, or, at least, exists 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 Conservative 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 tells 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 mental 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 Bennett’s (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 is 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 toward 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 eve n 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.
 Contemporary philosophy of mind, following cognitive science, uses the term ‘representation’ to mean just about anything that can be semantically evaluated. Thus, representations may be said to be true, to refer, to be accurate, and so forth. Representation thus conceived comes in many varieties. The most familiar are pictures, three-dimensional models, e.g., statues, scale model, linguistic text (including mathematical formulas) and various hybrids of these such as diagrams, maps, graphs and tables. It is an open question in cognitive science whether mental representation, which is our real topic, but at which time it falls within any of these or any-other familiar provinces.
 The representational theory of cognition and thought is uncontroversial in contemporary cognitive science that cognitive processes are processes that manipulate representations. This idea seems nearly inevitable. What makes the difference between processes that are cognitive-solving a problem, say and those that are not-a patellar reflex, for example-is just that cognitive processes are epistemically assessable? A solution procedure can be justified or correct, as a reflex cannot. Since only things with content can be epistemically assessed, processes appear to count as cognitive only in so far as they implicate representations.
 It is tempting to think that thoughts are the mind’s representations: Are not thoughts just those mental states that have semantic content? This is, no doubt, harmless enough provided we keep in mind that cognitive science may attribute to thought’s properties and contents that are foreign too common-sense. First, most of the representations hypothesized by cognitive science do not correspond to anything common-sense would recognize as thoughts. Standard psycholinguistic theory, for instance, hypothesizes the construction of representations of the syntactic structures of the utterances one hears and understands. Yet we are not aware of, and non-specialists do not even understand, the structures represented. Thus, cognitive science may attribute thoughts where common-sense would not. Second, cognitive science may find it useful to individuate thoughts in ways foreign too common-sense.
 However,  concepts occupy mental states having content: A belief may have the content that I will catch the train, or a hope may have the content that the prime minister will resign. A concept is something which is capable of being a constituent of such contents. More specifically, a concept is a way of thinking of something-a particular object, or property, or relation, or some other entity.
 Several different concepts may each be ways of thinking of the same object. A person may think of himself in the first-person pronoun, or think of himself as the spouse of Julie Smith, or as the person located in a certain room now. More generally, a concept ‘c’ is such-and-such, without believing ‘d’ is such-and-such. As words can be combined to form structured sentences, concepts have also been conceived as combinable into structured complex contents. When these complex contents are expressed in English by ‘that . . . ‘ clauses, as in our opening examples, they will be capable of being true or false, depending on the way the world is.
 A fundamental question for philosophy is: What individuates a given concept-that is, what makes it the one it is, than any other concept? One answer, which has been developed in great detail, is that it is impossible to give a non-trivial answer to this question (Schiffer, 1987). An alternative approach, favoured by most, addresses the question by starting from the idea that a concept is individuated by the condition which must be satisfied if a thinker is to possess that concept and to be capable of having beliefs and other contributing attributes whose contents contain it as a constituent. So, to take a simple case, one could propose that the logical concept -‘and’- is individuated by this condition: It is the unique concept ‘C’ to posses which a thinker has to find these forms of inference compelling, without basing them on any further inference or information: From any two premisses ‘A’ and ‘B’, ‘ABC’ can be inferred, and from any premiss ‘ABC’, each, of ‘A’ and ‘B’ can be inferred. Again, a relatively observational concept such as ‘round’ can be individuated in part by stating that the thinker finds specified contents containing it compelling when he has certain kinds of perception, and in part by relating those judgements containing the concept and which are not based on perception to those judgements that are. A statement which individuates a concept by saying what is required for a thinker to possess it can be described as giving the ‘possession condition’ for the concept.
 A possession condition for a particular concept may actually make use of that concept. The possession condition for ‘and’, does not. We can also expect to use relatively observational concepts in specifying the kind of experiences, least of mention, to which have to be made in defence of 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 attributes attributed to the thinker in the possession condition. Otherwise we would be presupposed possession of the concept in an account which 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 a thinker’s mastery of a concept is inextricably tied to how he 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 which 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’s, 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 a thinker to poses 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 concept 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 condition may in various way’s make a thinker’s possession of a particular concept dependent on or upon his relations to his environment. Many possession conditions will mention the links between a concept and the thinker’s perceptual experience. Perceptual experience represents the world for being 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 subject’s 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 to the thinker. Burge (1979) has also argued from intuitions about particular examples that, even though the thinker’s non-environmental properties and relations remain constant, the conceptual content of his mental state can vary if the thinker’s social environment is varied. A possession condition which properly individuates such a concept must take into account 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 which is dependent in part on or upon the identity of the concept. The normative character of concepts also extends into the territory of a thinker’s reasons for making judgements. A thinker’s visual perception can give him good reason for judging ‘That man is 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 a concept, and consider how the referent of the 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 in the possession condition always lead to true judgements and truth-preserving inferences. This proposal would explain why certain reasons are necessarily good reasons for judging given contents. Provided the possession condition permits us to say what it is about a thinker’s previous judgements that make it the case that he is employing one concept than another, this proposal would also have another virtue. It would also 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 had the property which in fact makes the judgement practices in the possession condition yield true judgements, or truth-preserving inferences.
 What is more that innate ideas have been variously defined by philosophers either as ideas consciously presented, to the mind prior to sense experience (the-dispositional sense), or as ideas which we have an innate disposition to form, though we need not be actually aware of them at any particular time, e.g., as babies ~ in cases in a dispositional sense?
 Understood in either way they were invoked to account for our recognition of certain truths without recourse to experiential truths without recourse verification, such as those of mathematics, or justify certain moral and religious claims which were held to be capable of being known by introspection of our innate ideas. Examples of such supposed truths might include ‘murder is wrong’ or ‘God exists’.
 One difficulty with the doctrine is that it is sometimes formulated as one about concepts or ideas which are held to be innate and at other times as one about a source of propositional knowledge. In so far as concepts are taken to be innate, the doctrine relates primarily to claim about meaning: Our idea of God, for example, is taken as a source for the meaning of the word God. When innate ideas are understood propositionally, supposed innateness is taken as evidence for their truth. However, this clearly rests the assumption that innate prepositions have an unimpeachable source, usually taken to be God, but then any appeal to innate ideas to justify the existence of God is circular. Despite such difficulties the doctrine of innate ideas had a long and influential history until the eighteenth century and the concept has in recent decades been revitalized through its employment in Noam Chomsky’s influential account of the mind’s linguistic capabilities.
 The attraction of the theory has been felt strongly by those philosophers who have been unable to give an alternative account of our capacity to recognize that some proposition cannot be justified solely on the basis of an appeal to sense experience. Wherefore, Plato argued that, for example, recognition of mathematical truths could only be explained on the assumption of some form of recollection. Since there was no plausible post-natal source the recollection must refer back to a pre-natal acquisition of knowledge. Thus understood, the doctrine of innate ideas supposed the thoughts that there were important truths innate in human beings and the senses hindered their proper apprehension.
 The ascetic implications of the doctrine were important in Christian philosophy throughout the Middle Ages and the doctrine featured powerfully in scholastic teaching until its displacement by Locke’s philosophy in the eighteenth century. It had in the meantime acquired modern expression in the philosophy of Descartes who argued that we can come to know certain important truths before we have any empirical knowledge at all. Our ideas of God, for example, and our coming to recognize that God must necessarily exist, are, Descartes held, logically independent of sense experience. In England the Cambridge Platonists such as Henry Moore and Ralph Cudworth added considerable support.
 Locke’s rejection of innate ideas and his alternative empiricist account was powerful enough to displace the doctrine from philosophy almost totally. Leibniz, in his critique of Locke, attempted to defend it with a sophisticated dispositional version of the theory, but it attracted few followers.
 The empiricist alternative to innate ideas as an explanation of the certainty of propositions was in the direction of construing all necessary truths as analytic. Kant’s refinement of the classification of propositions with the fourfold distinction, analytic/synthetic and a priori/a posteriori did nothing to encourage a return to the innate idea’s doctrine, which slipped from view. The doctrine may fruitfully be understood as the production of confusion between explaining the genesis of ideas or concepts and the basis for regarding some propositions as necessarily true.
 Nevertheless, according to Kant, our knowledge arises from two fundamentally different faculties of the mind, sensibility and understanding. He criticized his predecessors for running these faculties together. Leibniz for treating sensing as a confused mode of understanding and Locke for treating understanding as an abstracted mode of sensing. Kant held that each of the faculties operates with its own distinctive type of mental representation. Concepts, the instruments of the understanding, are mental representations that apply potentially to many things in virtue of their possession of a common feature. Intuitions, the instrument of sensibility, are representations that refer to just one thing and to that thing is played in Russell’s philosophy by ‘acquaintance’ though intuition’s objects are given to us, Kant said; ‘Through concepts they are thought’.
 Nonetheless, it is famous Kantian Thesis that knowledge is yielded neither by intuitions nor by concepts alone, but only by the two in conjunction, ‘Thoughts without content are empty’, he says in an often quoted remark, and ‘intuitions without concepts are blind’. Exactly what Kant means by the remark is a debated question, however, answered in different ways by scholars who bring different elements of Kant’s text to bear on it. A minimal reading is that it is only propositionally structured knowledge that requires the collaboration of intuition and concept: This view allows that intuitions without concepts constitute some kind of non-judgmental awareness. A stronger reading is that it is reference or intentionality that depends on intuition and concept together, so that the blindness of intuition without concept is its referring to an object. A more radical view, yet is that intuitions without concepts are indeterminate, a mere blur, perhaps nothing at all. This last interpretation, though admittedly suggested by some things Kant says, is at odds with his official view about the separation of the faculties.
 Least that ‘content’ has become a technical term in philosophy for whatever it is a representation had that makes it semantically evaluable. Wherefore, a statement is sometimes said to have a proposition or truth condition as its content, whereby its 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 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 underwrite is its semantic evaluation
 One difficulty with the doctrine is that it is sometimes formulated as one about concepts or ideas which are held to be innate and at other times as one about a source of propositional knowledge. In so far as concepts are taken to be innate, the doctrine relates primarily to claim about meaning: Our idea of God, for example, is taken as a source for the meaning of the word God. When innate ideas are understood propositionally, their supposed innateness is taken as evidence for their truth. However, this clearly rests the assumption that innate prepositions have a source, usually taken to be God, but then any appeal to innate ideas to justify the existence of God is circular. Despite such difficulties the doctrine of innate ideas had a long and influential history until the eighteenth century and the concept has in recent decades been revitalized through its employment in Noam Chomsky’s influential account of the mind’s linguistic capabilities.
 Least that ‘content’ has become a technical term in philosophy for whatever it is a representation had that makes it semantically evaluable. Wherefore, a statement is sometimes said to have a proposition or truth condition as its content, whereby its 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 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 underwrite is its semantic evaluation.
 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 entails psychological certainty. Nonetheless, there are arguments against all versions of the thesis that knowledge requires having a belief-like attitude toward the known. These argument s are given by philosophers who think that knowledge and belief, or a facsimile, are mutually incompatible (the incompatibility thesis), or by ones who say that knowledge does not entail belief, or vice versa, so that each may exist without the other, however, the two may also coexist of the separability thesis.
 The incompatibility thesis is sometimes traced to Plato in view of his claim that knowledge is infallible while belief or opinion is fallible (in the ‘Republic’). Nonetheless 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 cites linguistic evidence to back up the incompatibility thesis. He notes that people oftentimes say ‘I don’t 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 didn’t hurt him, you killed him’.
 H.A. Prichard (1966) offers a defence of the incompatibility thesis which hinges on the equation of knowledge with certainty, as both infallibility and psychological certitude gives the assumption that when we believe in the truth of a claim we are not certain about its truth. Given that knowledge never does, believing something rules out the possibility of knowing it. Unfortunately, Prichard gives us no-good reason to grant that states of belief are never ones involving confidence. Conscious beliefs clearly involve some level of confidence, only to suggest that 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, whereas knowledge can exist in the absence of confidence about the item known, although knowledge might also be accompanied by confidence as well. Woozley’s 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 its correct’. Nonetheless, 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 sure of whether 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, which Walter has forgotten that he learned some English history years prior and yet he is able to give several correct responses to questions such as ‘When did the Battle of Hastings occur’? Since he forgo t that he took history, he considers his correct responses to be no more than guesses. Nonetheless, 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 fortiori he would deny being sure, or having the right to be sure, that, nonetheless that 1066 was the correct date. Radford would nonetheless insist that Walter knows when the Battle occurred, since clearly he remembered the correct date. Radford admits that it would be inappropriate for Walter to say that he knew when the Battle of Hastings occurred, least of mention, that Woozley attributes the impropriety to a fact about when it is not appropriate to claim knowledge. When we claim knowledge, we ought, at least, believe that we have the knowledge we claim, or else our behaviour is, intentionally misleading’.
 Those who 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 Walter lack’s beliefs about English history is plausible on this Cartesian picture since Walter does not find himself with any beliefs about English history when he seeks them out. One might criticize Radford, however, by rejecting the Cartesian view of belief. One could argue that some beliefs are thoroughly unconscious, for example. Or one could adopt a behaviorist 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 hasn’t Radford already adopted a behaviourist conception of knowledge?) Since Walter gives the correct response when queried, a form of verbal behaviour, a behaviorist would be tempted to credit him with the belief that the Battle of Hastings occurred in 1066.
 D.M.Armstrong (1973) takes a different tack against Radford, Walter does know that the Battle of Hastings took place in 1066. Armstrong will grant Radford that point, however, Armstrong suggests that Walter believes 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. What is more that Armstrong insists, Walter also believes that the Battle did occur in 1066? After-all, had Walter been mistaught that the Battle occurred in 1066, and had he forgotten being ‘taught’ this and subsequently ‘guessed’ that it took place in 1066, we would surely describe the situation as one in which Walter’s false belief about the Battle became unconscious over time but persisted as a memory trace that was causally responsible for his guess. Out of consistency, we must describe Radford’s original case as one in which Walter’s true belief became unconscious but persisted long enough to cause his guess. Wherefore, Walter 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 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. If Armstrong is correct in suggesting that Walter believes both that 1066 is and that is not the date of the Battle of Hastings, one might deny Walter knowledge on the grounds that people who believe the denial of what they believe cannot be aid to know the truth of their belief. Another strategy might be to liken the examinee case to examples of ignorance given in recent attacks on ‘externalisms’. This account of knowledge (needless to say, externalists themselves would tend not to favour this strategy). Consider the following case developed by BonJour (1895): 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, 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 arrived at her belief about the whereabouts of the President through 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 little different. Even if Walter lacks the belief which Radford denies him, Radford does not have an example of knowledge that is unattended with belief. Suppose that Walter’s memory had been sufficiently powerful to produce the relevant belief. As Radford says, Walter has every reason to suppose that his response is merely guesswork, and so he has every reason to consider his belief as false. His belief would be an irrational one, and wherefore, one about whose truth Walter would be ignorant.
 The externalism/internalism distinction has been mainly applied if it requires that all of the factors needed for a belief to be epistemically justified for a given person be cognitively accessible to that person. However, epistemologists often use the distinction between internalist and externalist theories of epistemic justification without offering any explicit explication. Also, it has been applied in a closely related way to accounts of knowledge and in a rather different way to accounts of belief and thought content.
 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. Similarly, a coherentist view could also be internalist, if both he beliefs or other states with which a justificadum belief is required to cohere and the coherence relations themselves are reflectively accessible.
 Also, on this way of drawing the distinction, a hybrid view 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 externalists view. Noticeably, its view that was externalist in relation to forms or versions of internalist, that by not requiring that the believer actually be aware of all justifying factors could still be internalist in relation for which requiring that he 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 belief be produced in a way or via a process that makes it 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, rather than offering a competing account of the same concept of epistemic justification with which the traditional epistemologist is concerned, has simply charged the subject.
 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 of language more specifically from the various phenomena pertaining to natural kind terms, indexical, and so forth. 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 dependent on facts about his environment, e.g., whether he is on Earth or Twin Earth, what in fact he is pointing at, the classificatory criteria employed by the experts in his social group, and so forth. , -not just on what is going on internally in his mind or brain.
 An objection to externalist accounts of content is that they seem unable to do justice to our ability to know the contents of our beliefs or thoughts ‘from the inside’, simply by reflection. If content is dependent on external factors pertaining to the environment, the n 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 account of justification: That, if part or all of the content of a belief is inaccessible to the believer, then both the justifying status of other beliefs in relation to the content and the status of that 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.
 If the world is radically different from the way it appears, to the pointy that apparent epistemic vices are actually truth-conducive, presumably his should not make us retrospectively term such vices ‘virtues’ even if they are and have always been truth-conducive. Suggestively, it would simply make the epistemic virtue qualities which a truth-desiring person would want to have. For even if, unbeknown to us, some wild sceptical possibility is realized, this would not affect our desires (it being, again, unknown). Such a characterization, moreover, it would seem to fit the virtues in our catalogue. Almost by definition, the truth-desiring person would want to be epistemically conscientious. And, given what seem to be the conditions pertaining to human life and knowledge, the truth-desiring person will also want to have the previously cited virtues of impartiality and intellectual courage.
 Are, though, truth and the avoidance of error rich enough desires for the epistemically virtuous? Arguably not. For one thing, the virtuous inquirer aims not so much at having true beliefs as at discovering truths-a very different notions. Perpetual reading of a good encyclopaedia will expand my bank of true beliefs without markedly increasing human-kinds basic stock of truths. For Aristotle, too, one notes that true belief is not, as such, even a concern: The concern, is the discovery of scientific or philosophical truth. But, of course, the mere expansion of our bank of truths-even of scientific and philosophical truths-is not itself the complete goal of its present. Rather one looks for new truths of an appropriate kind-rich, deep, explanatorily fertile, say. By this reckoning, then, the epistemically virtuous person seeks at least three related, but separate ends, to discover new truths, to increase one’s explanatory understanding, to have true than false beliefs.
 Another important area of concern for epistemologists is the relation between epistemic virtue and epistemic justification. Obviously, an epistemically virtuous person must itself, I take it, be virtuous. But is a virtuously formed belief automatically a justified one? I would hold that if a belief is virtuously formed, this fully justifies that person in having it: However, the belief itself may lack adequate justification, as the evidence for it may be, through no fault of this person, still inadequate. Different philosophers on this point or points, are, however, apparently to have different intuitions.
 Hegel’s theory of justification contains both ‘externalist’ and ‘coherentist’ elements. He recognizes that some justification is provided by percepts and beliefs being generated reliably by our interaction with the environment. Hegel contends that full justification additionally requires a self-conscious, reflective comprehension of one’s beliefs and experiences which integrate them into a systematic conceptual scheme which provides an account for them which is both coherent and reflexively self-consistent.
 Hegel contends that the corrigibility of conceptual categories is a social phenomenon. Our partial ignorance about the world can be revealed and corrected because one and the same claim or principle can be applied, asserted and assessed by different people in the same context or by the same person in different contexts. Hegel’s theory of justification requires that an account be shown to e adequate to its domain and to be superior to its alternatives. In this regard, Hegel is a fallibility according to whom justification is provisional and ineluctably historical, since it occurs against the background of less adequate alternative views.
 Meanwhile, one important difference between the sceptical approach and more traditional ones becomes plain when the two are applied to sceptical questions. On the classical view, if we are to explain how knowledge is possible, it is illegitimate to make use of the resources of science, this would simply beg the question against the sceptic by making use of the very knowledge which he calls into question. Thus, Descartes’ attempt to answer the sceptic begins by rejecting all those beliefs about which any doubt is possible. Descartes must respond to the sceptic from a starting place which includes no beliefs at all. Naturalistic epistemologists, however, understand the demand to explain the possibility of knowledge differently. As Quine argues, sceptical question arise from within science. It is precisely our success in understanding the world, and thus, in seeing that appearance nd reality may differ, that raises the sceptical question in the first place. We may thus legitimately use the resources of science to answer the question which science itself has raised. The question about how knowledge is possible should it be construed as an empirical question: It is a question about how creatures such as we (given what our best current scientific theories tell us we are like) may come to have our best current scientific theories tell us the world is like. Quine suggests that the Darwinian account of the origin of species gives a very general explanation of why it is that we should be well adapted to getting true beliefs about our environment, while an examination of human psychology will fill the details of such an account. Although Quine himself does not suggest it, and so, investigations in the sociology of knowledge are obviously relevant as well.
 This approach to sceptical questions clearly makes them quite tractable, and its proponents see this, understandably, as an important advantage of the naturalistic approach. It is in part for this reason that current work in psychology and sociology is under such close scrutiny by many epistemologists. By the same token, the detractors of the naturalistic approach argue that this way of dealing with sceptical questions simply bypasses the very questions which philosophers have long dealt with. Far from answering the traditional sceptical question it is argued, the naturalistic approach merely changes the topic. Debates between naturalistic epistemologists and their critics, in that frequently focus on whether this new way of doing epistemology adequately answers, transforms or simply ignores the questions which others see as central to epistemological inquiry. Some see the naturalistic approach as an attempt to abandon the philosophical study of knowledge entirely.
 In thinking about the possibilities that we bear on in mind, our conscious states, according to Franz Brentano (1838-1917), are all objects of ‘inner perception’. Every such state is such that, for the person who is in that state, it is evident to that person that he or she is in that state, least of mention, that each of our conscious states is not an object of an act of perception, wherefore the doctrine does not lead to an infinite regress.
 Brentano holds that there are two types of conscious state-those that are ‘physical’ and those are ‘intentional’ a ‘physical’, or sensory, state is a sensation or sense-impression-a qualitative individual composed of parts that are spatially related to each other. ‘Intentional’ states, e.g., believing, considering, hoping, desiring which are characterized by the facts that (1) they are ‘directed upon objects’. (2) objects may be ‘directed upon’, e.g., we may fear things that do not exist, and (3) such states are not sensory. There is no sensation, no sensory individual, that can be identified with any particular intentional attitude.
 Following Leibniz, Brentano distinguishes two types of certainty: The certainty we can have with respect to the existence of our conscious states, and that a priori certainty that may be directed upon necessary truths. These two types of certainty may be combined in a significant way. At a given, moments I may be certain, on the basis of inner perception, that there is believing, desiring, hoping and fearing, and L may also be certain a priori that there cannot be believing, desiring, hoping, and fearing unless there is a ‘substance’ that believes, desires, hopes and fears. In such a case, it will be certain for me [as I will perceive] that there is a substance that believes, desires, hopes and fears. It is also axiomatic. Brentano says, that, if one is certain that a substance of a certain sort exists, then one is identical with that substance.
 Brentano makes use of only two purely epistemic concepts, that of ‘being’ certain, or ‘evident’, and that of ‘being probable’. If a given hypothesis is probable, in the epistemic sense, for a particular person, then that person can be certain that the hypothesis is probable for him. Making use of the principles of probability, one may calculate the probability that a given hypothesis has on one’s evidence base.
 Nonetheless, if our evidence-base is composed only of necessary truths and the facts of inner perception, then it is difficult to see how it could provide justification for any contingent truths other than those that pertain to states of consciousness. How could such an evidence-base even lend ‘probability’ to the hypothesis that there is a world of external physical things?
 What, then, is the problem of the external world? Certainly it is not whether there is an external world as this is taken for granted. Instead, the problem is an epistemological one which, in a rough approximation, can be formulated by asking whether and if so how a person gains knowledge of the external world. However, the problem seems to admit of an easy solution. There is knowledge of the external world which persons acquire primarily by perceiving objects and events which make up the external world.
 An epistemic argument would concede that the main reason for this in 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-inferential. It is claimed that perceptual knowledge that there is a brown and rectangular table before me, because I would not 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 a preposition about appearances. If so, epistemological direct realism is false.
 The significance of this emerges when one asks of a particular application that by what evidence or by what consideration is the best answer, clearly, is to question with which the argument will lead to the problems of the external world and the epistemological direct realism. That is, the crucial question is whether any part of the argument from illusion really forces us to abandon perceptual direct realism. The clear implication of the world perceived from the answer is ‘no’, we may point that a key premise in the relativity argument links how something appears with direct perception: The fact that the object of appear is supposed to entail that one directly perceives something which is otherwise an attributing state with content. 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 (Chisholm, 1964). And there are countless other examples that are similarly like this one.
 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 he like. Such a move, moreover, requires an argument 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 possibly be.
 If the argument from illusion is defused, the major threat facing, perceptual direct realism will have been removed. So, that, there will no longer be any real motivation for the problem of the external world, of course, even if a perceptual direct realism is reinstated, this does not solve that the argument from illusion may suffice to refute all forms of perceptual realism. That problem, nonetheless, might arise even for one who accepts the perceptual direct realism, however, there is reason to be suspicious. What is not clear is whether the dependence is ‘epistemic’ or ‘semantic’. It is epistemic if, in order to understand what it is to see something blue, one must also understand what it is for something to look blue. However, 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 dependence 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 objects appear, but this fact does not impugn their knowledge that they are seeing, e.g., blue objects.
 This criticism means that representational states used for the problem of the external world is narrow, in the sense that it focuses only on individual elements within the argument on which the argument seems to be used. Those assumptions, are foundationalist in character: Knowledge and justified belief are divided into the basic, immediate and non-inferential cases, and the non-basic, inferential knowledge and justified belief which is supported by the basic. That is to say, however, though foundationalism was widely assumed when the problem of the external world was given currency in Descartes and the classical empiricists. It has been readily challenged and there are in place well-worked alterative accounts to knowledge and justified belief, some of which seem to be plausible as the most tenable version of foundationalism. So we have some good reason to suspect, quite as one might have initially thought, that the problem of the external world just does not arise, at least not in the forms in which it has usually been presented.
 In contrast with the possibility of asking and answering to questions is very closely bound up with the fact that the problem with the external world or direct realism  takes place relative to or from a point or points of reference, which does or does not have an origin. In addition to this, the significance of this emerges when one asks, that an object is a unified and coherent segment of the perceived array that can be perceived as having certain properties and as standing in certain relations to other objects (such as the property of having a determinate shape.) One way of putting this distinction, derived ultimately by Alexius Meinong, whose intentional attitude that we ordinarily call ‘perceiving’ and ‘remembering’, provide ‘presumptive evidence’, that is to say, prima facie evidence-for their intentional objects. For example, believing that one is looking at a group of people tends to justify the belief that there is a group of people that one is looking at. How, then, are we to distinguish merely ‘prima facie’ justification from the real thing? This type of solution would seem to call for principles that specify, by reference to further facts of inner perception, the conditions under which merely prima facie justification may become real justification.
 Those who speak of prima facie reasons may do so in either of two ways (1) we have a prima facie duty to keep our promise if every action if every action of promise-keeping is to that extent right-if all actions of promise-keeping are the better for it, and (2) an action may be a prima facie duty in virtue of some property it has, in this sense even though it is wrong overall, and so not a ‘duty proper’.
 However, what is required is an account of simply describing developmental progress that can be gained or articulated by one’s thoughts. That for developmental considerations do circumscribe the form that such an account will take in virtue of logical positivism, but it cannot be conclusive until we have looked more closely at the bases on which the relevant and distinguishable contents make clear to accommodate a different thought from that to be the functional dynamic areas, from which strongly suggests that in the move from implicit to explicit understanding involves our developing ability than purely reactive, manifestation of the relevant representational abilities.
 It was ‘positivism’ in its adherence to the doctrine the within the paradigm of science is the only form of knowledge and that there is nothing in the universe beyond what can in principle be scientifically known. It was ‘logical’ in its dependence on developments in logic and mathematics in the early years of this century which were taken to reveal how a priori knowledge of necessary truths is compatible with a thoroughgoing empiricism.
 The exclusiveness of a scientific world-view was to be secured by showing that everything beyond the reach of science is strictly or ‘cognitively’ meaningless. In the sense of being incapable of truth or falsity, and so not a possible object of cognition. This required a criterion of meaninglessness, and it was found in the idea of empirical verification. 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 verbified 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. The criterion is accordingly to be understood to require only verifiability or fallibility, in the sense of empirical evidence which would count either for or against the truth of the sentence in question, without having to logically imply it. Verification or confirmation is not necessarily something that can be carried out by the person who entertains the sentence or hypothesis in question, or even by anyone at all at the stage of intellectual and technological development achieved at the time it is entertained. A sentence is cognitively meaningful if and only if it is in principle empirically verifiable or falsifiable.
 Anything which does not fulfil this criterion is declared literally meaningless. There is no significant ‘cognitive’ question as to its truth or falsity: It is not an appropriate object of enquiry. Moral and aesthetic and other ‘evaluative’ sentences are held to be neither confirmable nor disconfirmable on empirical grounds, and so are cognitively meaningless. They are, at best, expressions of feeling or preference which are neither true nor false. Whatever is cognitively meaningful and therefore factual is value-free. The positivists claimed that many of the sentences of traditional philosophy, especially those in what they called ‘metaphysics’, also lack cognitive meaning and say nothing that could be true or false. But they did not spend much time trying to show this in detail about the philosophy of the past. They were more concerned with developing a theory of meaning and of knowledge adequate to the understanding nd perhaps even the improvement of science.
 Nevertheless, that our beliefs are not only in bodies, but also in persons, or themselves, which continue to exist through time, and this belief too can be explained only by the operation of certain ‘principles of the imagination’. We never directly perceive anything we can call ourselves: The most we can be aware of in ourselves are our constantly changing momentary perceptions, not the mind or self which has them. For Hume (1711-76), there is nothing that really binds the different perceptions together, we are led into the ‘fiction’ that they form a unity only because of the way in which the thought of such series of perceptions works upon the mind. ‘The mind is a kind of theatre, where several perceptions successively make their appearance,  . . .   there is properly no simplicity in it at one time, nor identity in different: Whatever natural propensity we may have to imagine that simplicity and identity. The comparison of the theatre must not mislead us. They are the successive perceptions only, that constitutes the mind.
 Leibniz held, in opposition to Descartes, that adult humans can have experiences of which they are unaware: Experiences of which effect what they do, but which are not brought to self-consciousness. Yet there are creatures, such as animals  and infants, which completely lack the ability to reflect of their experiences, and to become aware of them as experiences of theirs. The unity of a subject’s experience, which stems from his capacity to recognize all his experience as his, was dubbed by Kant ‘ as the transcendental unity of an apperception ~ Leibniz’s term for inner awareness or self-consciousness. But, in contrast with ‘perception’ or ‘outer awareness’ ~ though, this apprehension of unity is transcendental, than empirical, it is presupposed in experience and cannot be derived from it. Kant used the need for this unity as the basis of his attemptive scepticism about the external world. He argued that my experiences could only be united in one-self-consciousness, if, at least some of them were experiences of a law-governed world of objects in space. Outer experience is thus a necessary condition of inner awareness.
 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 which is dependent in part on or upon the identity of the concept. The normative character of concepts also extends into the territory of a thinker’s reasons for making judgements. A thinker’s visual perception can give him good reason for judging. ‘For a concept, and consideration how the referent of the 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 in the possession condition always lead to true judgements and truth-preserving inferences. This proposal would explain why certain reasons are necessarily good reasons for judging given contents. Provided the possession condition permits us to say what it is about a thinker’s previous judgements that make it the case that he is employing one concept than another, this proposal would also have another virtue. It would also 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 had the property which in fact makes the judgement practices in the possession condition yield true judgements, or truth-preserving inferences.
 What is more that innate ideas have been variously defined by philosophers either as ideas consciously present to the mind prior to sense experience (the-dispositional sense), or as ideas which we have an innate disposition to form (though we need not be actually aware of them at any particular time, e.g., as babies)-the dispositional sense?
 Understood in either way they were invoked to account for our recognition of certain truths without recourse to experiential truths without recourse verification, such as those of mathematics, or justify certain moral and religious claims which were held to be capable of being known by introspection of our innate ideas. Examples of such supposed truths might include ‘murder is wrong’ or ‘God exists’.
 One difficulty with the doctrine is that it is sometimes formulated as one about concepts or ideas which are held to be innate and at other times as one about a source of propositional knowledge. In so far as concepts are taken to be innate, the doctrine relates primarily ti claim about meaning: Our idea of God, for example, is taken as a source for the meaning of the word God. When innate ideas are understood propositionally, their supposed innateness is taken as evidence for their truth. However, this clearly rests the assumption that innate prepositions have an unimpeachable source, usually taken to be God, but then any appeal to innate ideas to justify the existence of God is circular. Despite such difficulties the doctrine of innate ideas had a long and influential history until the eighteenth century and the concept has in recent decades been revitalized through its employment in Noam Chomsky’s influential account of the mind’s linguistic capabilities.
 The attraction of the theory has been felt strongly by those philosophers who have been unable to give an alternative account of our capacity to recognize that some proposition cannot be justified solely on the basis of an appeal to sense experience. Thus Plato argued that, for example, recognition of mathematical truths could only be explained on the assumption of some form of recollection. Since there was no plausible post-natal source the recollection must refer back to a pre-natal acquisition of knowledge. Thus understood, the doctrine of innate ideas supposed the view that there were important truths innate in human beings and it was the senses which hindered their proper apprehension.
 The ascetic implications of the doctrine were important in Christian philosophy throughout the Middle Ages and the doctrine featured powerfully in scholastic teaching until its displacement by Locke’s philosophy in the eighteenth century. It had in the meantime acquired modern expression in the philosophy of Descartes who argued that we can come to know certain important truths before we have any empirical knowledge at all. Our idea of God, for example, and our coming to recognize that God must necessarily exist, are, Descartes held, logically independent of sense experience. In England the Cambridge Platonists such as Henry More and Ralph Cudworth added considerable support.
 Locke’s rejection of innate ideas and his alternative empiricist account was powerful enough to displace the doctrine from philosophy y almost totally. Leibniz, in his critique of Locke, attempted to defend it with a sophisticated dispositional version of the theory, but it attracted few followers.
 The empiricist alternative to innate ideas as an explanation of the certainty of propositions was in the direction of construing all necessary truths as analytic. Kant’s refinement of the classification of propositions with the fourfold distinction, analytic/synthetic and a priori/a posteriori did nothing to encourage a return to the innate idea’s doctrine, which slipped from view. The doctrine may fruitfully be understood as the production of confusion between explaining the genesis of ideas or concepts and the basis for regarding some propositions as necessarily true.
 Nevertheless, according to Kant, our knowledge arises from two fundamentally different faculties of the mind, sensibility and understanding. He criticized his predecessors for running these faculties together. Leibniz for treating sensing as a confused mode of understanding and Locke for treating understanding as an abstracted mode of sensing. Kant held that each of the faculties operates with its own distinctive type of mental representation. Concepts, the instruments of the understanding, are mental representations that apply potentially to many things in virtue of their possession of a common feature. Intuitions, the instrument of sensibility, are representation that refer to just one thing and to that thing is played in Russell’s philosophy by ‘acquaintance’ though intuition’s objects are given to us, Kant said; Through concepts they are thought.
 ‘Thoughts without content are empty’, he says in an often quoted remark, and ‘intuitions without concepts are blind’. Exactly what Kant means by the remark is a debated question, however, answered in different ways by scholars who bring different elements of Kant’s text to bear on it. A minimal reading is that it is only propositionally structured knowledge that requires the collaboration of intuition and concept: This view allows that intuitions without concepts constitute some kind of non-judgmental awareness. A stronger reading is that it is reference or intentionality that depends on intuition and concept together, so that the blindness of intuition without concept is its referring to an object. A more radical view, yet is that intuitions without concepts are indeterminate, a mere blur, perhaps nothing at all. This last interpretation, though admittedly suggested by some things Kant says, is at odds with his official view about the separation of the faculties.
 Least that ‘content’ has become a technical term in philosophy for whatever it is a representation had that makes it semantically evaluable. Wherefore, a statement is sometimes said to have a proposition or truth condition as its content, whereby its term is sometimes said to have a concept as it s 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 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 underwrite is its semantic evaluation.
 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 entails psychological certainty, or acceptance. Nonetheless, there are arguments against all versions of the thesis that knowledge requires having a belief-like attitude toward the known. These argument s are given by philosophers who think that knowledge and belief, or a facsimile, are mutually incompatible, that the incompatibility thesis, or by ones who say that knowledge does not entail belief, or vice versa, so ha t each may exist without the other, however, the two may also coexist of the separability thesis.
 The incompatibility thesis is sometimes traced to Plato in view of his claim that knowledge is infallible while belief or opinion is fallible (Republic). Nonetheless 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  cites linguistic evidence to back up the incompatibility thesis. He notes that people oftentimes say ‘I don’t 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 didn’t hurt him, you killed him’.
 H.A.Prichard (1966) offers a defence of the incompatibility thesis which hinges on the equation of knowledge with certainty, as both infallibility and psychological certitude gives the assumption that when we believe in the truth of a claim we are not certain about its truth. Given that knowledge never does, believing something rules out the possibility of knowing it. Unfortunately, Prichard gives us no-good reason to grant that states of belief are never ones involving confidence. Conscious beliefs clearly involve some level of confidence, only to suggest that 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, whereas knowledge can exist in the absence of confidence about the item known, although knowledge 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 s correct’. Nonetheless, 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 sure of whether 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 that Walter has forgotten that he learned some English history years prior 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 his correct responses to be no more than guesses. Nonetheless, 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 fortiori he would deny being sure, or having the right to be sure, that, nonetheless that 1066 was the correct date. Radford would nonetheless insist that Walter knows when the Battle occurred, since clearly he remembered the correct date. Radford admits that it would be inappropriate for Walter to say that he knew when the Battle of Hastings occurred, least of mention, that Woozley attributes the impropriety to a fact about when it is not appropriate to claim knowledge. When we claim knowledge, we ought, at least, believe that we have the knowledge we claim, or else our behaviour is ‘intentionally misleading’.
 Those who 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 Walter lack’s belief about English history is plausible on this Cartesian picture since Walter does not find himself with any beliefs about English history when he seeks them out. One might criticize Radford, however, by rejecting the Cartesian view of belief. One could argue that some beliefs are thoroughly unconscious, for example. Or one could adopt a behaviorist 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 hasn’t Radford already adopted a behaviourist conception of knowledge?) Since Walter gives the correct response when queried, a form of verbal behaviour, a behaviorist would be tempted to credit him with the belief that the Battle of Hastings occurred in 1066.
 D.M.Armstrong (1973) takes a different tack against Radford, Walter does know that the Battle of Hastings took place in 1066. Armstrong will grant Radford that points, however, Armstrong suggests that Walter believes 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. What is more that Armstrong insists, Walter also believes that the Battle did occur in 1066? After-all, had Walter been mistaught that the Battle occurred in 1066, and had he forgotten being ‘taught’ this and subsequently ‘guessed’ that it took place in 1066, we would surely describe the situation as one in which Walter’s false belief about the Battle became unconscious over time but persisted as a memory trace that was causally responsible for his guess. Out of consistency, we must describe Radford’s original case as one in which Walter’s true belief became unconscious but persisted long enough to cause his guess. Wherefore, Jan 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 claim that knowledge entails belief.
 The externalism/internalism distinction has been mainly applied if it requires that all of the factors needed for a belief to be epistemically justified for a given person be cognitively accessible to that person. However, epistemologists often use the distinction between internalist and externalist theories of epistemic justification without offering any explicit explication. Also, it has been applied in a closely related way to accounts of knowledge and in a rather different way to accounts of belief and thought content.
 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. Similarly, a coherentist view could also be internalist, if both he beliefs or other states with which a justificadum belief is required to cohere and the coherence relations themselves are reflectively accessible.
 Also, on this way of drawing the distinction, a hybrid view 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 position. Obviously too, a view that was externalist in relation to forms or versions of internalist, that by not requiring that the believer actually be aware of all justifying factors could still be internalist in relation for which requiring that he 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 via a process that makes it 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, rather than offering a competing account of the same concept of epistemic justification with which the traditional epistemologist is concerned, has simply charged the subject.
 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 of language more specifically from the various phenomena pertaining to natural kind terms, indexical, and so forth. 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 dependent on facts about his environment, e.g., whether he is on Earth or Twin Earth, what in fact he is pointing at, the classificatory criteria employed by the experts in his social group, and so forth. , -not just on what is going on internally in his mind or brain.
 An objection to externalist accounts of content is that they seem unable to do justice to our ability to know the contents of our beliefs or thoughts ‘from the inside’, simply by reflection. If content is dependent on external factors pertaining to the environment, the n 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 account of justification: That, if part or all of the content of a belief is inaccessible to the believer, then both the justifying status of other beliefs in relation to the content and the status of that 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.
 If the world is radically different from the way it appears, to the pointy that apparent epistemic vices are actually truth-conducive, presumably his should not make us retrospectively term such vices ‘virtues’ even if they are and have always been truth-conducive. Suggestively, it would simply make the epistemic virtue qualities which a truth-desiring person would want to have. For even if, unbeknown to us, some wild sceptical possibility is realized, this would not affect our desires (it being, again, unknown). Such a characterization, moreover, it would seem to fit the virtues in our catalogue. Almost by definition, the truth-desiring person would want to be epistemically conscientious. And, given what seem to be the conditions pertaining to human life and knowledge, the truth-desiring person will also want to have the previously cited virtues of impartiality and intellectual courage.
 Are, though, truth and the avoidance of error rich enough desires for the epistemically virtuous? Arguably not. For one thing, the virtuous inquirer aims not so much at having true beliefs as at discovering truths-a very different notion. Perpetual reading of a good encyclopaedia will expand my bank of true beliefs without markedly increasing human-kinds basic stock of truths. For Aristotle, too, one notes that true belief is not, as such, even a concern: The concern, is the discovery of scientific or philosophical truth. But, of course, the mere expansion of our bank of truths-even of scientific and philosophical truths-is not itself the complete goal of its present. Rather one looks for new truths of an appropriate kind-rich, deep, explanatorily fertile, say. By this reckoning, then, the epistemically virtuous person seeks at least three related, but separate ends, to discover new truths, to increase one’s explanatory understanding, to have true than false beliefs.
 Another important area of concern for epistemologists is the relation between epistemic virtue and epistemic justification. Obviously, an epistemically virtuous person must itself, I take it, be virtuous. But is a virtuously formed belief automatically a justified one? I would hold that if a belief is virtuously formed, this fully justifies that person in having it: However, the belief itself may lack adequate justification, as the evidence for it may be, through no fault of this person, still inadequate. Different philosophers on this point or points, ae, however, apparently to have different intuitions.
 Hegel’s theory of justification contains both ‘externalist’ and ‘coherentist’ elements. He recognizes that some justification is provided by percepts and beliefs being generated reliably by our interaction with the environment. Hegel contends that full justification additionally requires a self-conscious, reflective comprehension of one’s beliefs and experiences which integrates them into a systematic conceptual scheme which provides an account for them which is both coherent and reflexively self-consistent.
 Hegel contends that the corrigibly of conceptual categories is a social phenomenon. Our partial ignorance about the world can be revealed and corrected because one and the same claim or principle can be applied, asserted and assessed by different people in the same context or by the same person in different contexts. Hegel’s theory of justification requires that an account be shown to e adequate to its domain and to be superior to its alternatives. In this regard, Hegel is a fallibilist according to whom justification is provisional and ineluctably historical, since it occurs against the background of less adequate alternative views.
 Meanwhile, one important difference between the sceptical approach and to a greater extent traditional ones becomes plain when the two are applied to sceptical questions. On the classical view, if we are to explain how knowledge is possible, it is illegitimate to make use of the resources of science, this would simply beg the question against the sceptic by making use of the very knowledge which he calls into question. Thus, Descartes’ attempt to answer the sceptic begins by rejecting all those beliefs about which any doubt is possible. Descartes must respond to the sceptic from a starting place which includes no beliefs at all. Naturalistic epistemologists, however, understand the demand to explain the possibility of knowledge differently. As Quine argues, sceptical questions arise from within science. It is precisely our success in understanding the world, and thus, in seeing that appearance nd reality may differ, that raises the sceptical question in the first place. We may thus legitimately use the resources of science to answer the question which science itself has raised. The question about how knowledge is possible should it be construed as an empirical question: It is a question about how creatures such as we (given what our best current scientific theories tell us we are like) may come to have our best current scientific theories tell us the world is like. Quine suggests that the Darwinian account of the origin of species gives a very general explanation of why it is that we should be well adapted to getting true beliefs about our environment, while an examination of human psychology will fill the details of such an account. Although Quine himself does not suggest it, and so, investigations in the sociology of knowledge are obviously relevant as well.
 This approach to sceptical questions clearly makes them quite tractable, and its proponents see this, understandably, as an important advantage of the naturalistic approach. It is in part for this reason that current work in psychology and sociology is under such close scrutiny by many epistemologists. By the same token, the detractors of the naturalistic approach argue that this way of dealing with sceptical questions simply bypasses the very questions which philosophers have long dealt with. Far from answering the traditional sceptical question it is argued, the naturalistic approach merely changes the topic. Debates between naturalistic epistemologists and their critics, in that frequently focus on whether this new way of doing epistemology adequately answers, transforms or simply ignores the questions which others see as central to epistemological inquiry. Some see the naturalistic approach as an attempt to abandon the philosophical study of knowledge entirely.
 In thinking about the possibilities that we bear on in mind, our conscious states, according to Franz Brentano (1838-1917), are all objects of ‘inner perception’. Every such state is such that, the person who is in that state, it is evident to that person that he or she is in that state, least of mention, that each of our conscious states is not an object of an act of perception, wherefore the doctrine does not lead to an infinite regress.
 Brentano holds that there are two types of conscious state-those that are ‘physical’ and those are ‘intentional’ a ‘physical’, or sensory, state is a sensation or sense-impression-a qualitative individual composed of parts that are spatially related to each other. ‘Intentional’ states, e.g., believing, considering, hoping, desiring which are characterized by the facts that (1) they are ‘directed upon objects’. (2) objects may be ‘directed upon, e.g., we may fear things that do not exist, and (3) such states are not sensory. There is no sensation, no sensory individual, that can be identified with any particular intentional attitude.
 Following Leibniz, Brentano distinguishes two types of certainty: The certainty we can have with respect to the existence of our conscious states, and that a priori certainty that may be directed upon necessary truths. These two types of certainty may be combined in a significant way. At a given moment, I may be certain, on the basis of inner perception, that there is believing, desiring, hoping and fearing, and L may also be certain a priori that there cannot be believing, desiring, hoping, and fearing unless there is a ‘substance’ that believes, desires, hopes and fears. In such a case, it will be certain for me [as I will perceive] that there is a substance that believes, desires, hopes and fears. It is also axiomatic. Brentano says, that, if one is certain that a substance of a certain sort exists, then one is identical with that substance.
 Brentano makes use of only two purely epistemic concepts, that of ‘being’ certain, or ‘evident’, and that of ‘being probable’. If a given hypothesis is probable, in the epistemic sense, for a particular person, then that person can be certain that the hypothesis is probable for him. Making use of the principles of probability, one may calculate the probability that a given hypothesis has on one’s evidence base.
 Nonetheless, if our evidence-base is composed only of necessary truths and the facts of inner perception, then it is difficult to see how it could provide justification for any contingent truths other than those that pertain to states of consciousness. How could such an evidence-base even lend ‘probability’ to the hypothesis that there is a world of external physical things?
 The awareness generated by an introspective act can have varying degrees of complexity. It might be a simple knowledge of (mental) things’ ~ such as a particular perception-episode, or it might be the more complex knowledge of truths about  one’s own mind. In this latter full-blown judgement form, introspection is usually the self-ascription of psychological properties and, when linguistically expressed, results in statements like ‘I am watching the spider’ or ‘I am repulsed’.
 In psychology this deliberate inward look becomes a scientific method when it is ‘directed toward answering questions of theoretical importance for the advancement of our systematic knowledge of the laws and conditions of mental processes’. In philosophy, introspection (sometimes also called ‘reflection’) remains simply that notice which mind takes of its own operations and has been used to serve the following important functions:
  (1) Methodological: However, the fact that though experiments are a powerful addition in philosophical investigation. The Ontological Argument, for example, asks us to try to think of the most perfect being as lacking existence and Berkeley’s Master Argument challenges us to conceive of an unseen tree, conceptual results are then drawn from our failure or success. From such experiments to work, we must not only have (or fail to have) the relevant conceptions but also know that we have (or fail to have) them ~ presumably by introspection.
  (2) Metaphysical: A philosophy of mind needs to take cognizance of introspection. One can argue for ‘ghostly’ mental entities for ‘qualia’, for ‘sense-data’ by claiming introspective awareness of them. First-person psychological reports can have special consequences for the nature of persons and personal identity: Hume, for example, was content to reject the notion of a soul-substance because he failed to find such a thing by ‘looking within’. Moreover, some philosophers argue for the existence of additional perspectival facts ~ the fact of ‘what it is like’ to be the person I am or to have an experience of such-and-such-a-kind. Introspection as our access to such facts becomes important when we collectively consider the managing forms of a complete substantiation of the world.
  (3) Epistemological: Surprisingly, the most important use made of introspection has been in an accounting for our knowledge of the outside world. According to a foundationalist theory of justification an empirical belief is either basic and ‘self-justifying’ or justified in relation to basic beliefs. Basic beliefs therefore, constitute the rock-bottom of all justification and knowledge. Now introspective awareness is said to have a unique epistemological status in it, we are said to achieve the best possibly epistemological position and consequently, introspective beliefs and thereby constitute the foundation of all justification.
Coherence is a major player in the theatre of knowledge. There are coherence theories of belief, truth and justification where these combine in various ways to yield theories of knowledge, coherence theories of belief are concerned with the content of beliefs. Consider a belief you now have, the belief that you are reading a page in a book. So what makes that belief the belief that it is? What makes it the belief that you are reading a page in a book than the belief that you have something other that is elsewhere of a preoccupation? The same stimuli may produce various beliefs and various beliefs may produce the same action. The role that gives the belief the content it has is the role it plays within a network of relations to other beliefs, the role in inference and implication, for example, I infer different things from believing that I am reading a page in a book than from any other belief, just as I infer that belief from different things than I refer other belief’s form.
 The input of perception and the output of an action supplement the central role of the systematic relations the belief has to other beliefs, except that the systematic relations given to the belief specified of the content it has. They are the fundamental source of the content of beliefs. That is how coherence comes to be. A belief that the content that it does because of the away in which it coheres within the system of beliefs, however, weak coherence theories affirm that coherence is one determinant of the content of belief as strong coherence theories on the content of belief affirm that coherence is the sole determinant of the content of belief.
 Nonetheless, the concept of the given-referential immediacy as apprehended of the contents of sense experience is expressed in the first person, and present tense reports of appearances. Apprehension of the given is seen as immediate both in a causal sense, since it lacks the usual causal chain involved in perceiving real qualities of physical objects, and in an epistemic sense, since judgements expressing it are justified independently of all other beliefs and evidence. Some proponents of the idea of the ‘given’ maintain that its apprehension is absolutely certain: Infallible, incorrigible and indubitable. It has been claimed also that a subject is omniscient with regard to the given ~ if a property appears, then the subject knows this.
 Without some independent indication that some of the beliefs within a coherent system are true, coherence in itself is no indication of truth. Fairy stories can cohere, however, our criteria for justification must indicate to us the probable truth of our beliefs. Hence, within any system of beliefs there must be some privileged class with which others must cohere to be justified. In the case of empirical knowledge, such privileged beliefs must represent the point of contact between subject and world: They must originate within our descendable inherent perceptions of the world, that when challenged, however, we justify our ordinary perceptual beliefs about physical properties by appeal to beliefs about appearances. The latter seem more suitable as foundational, since there is no class of more certain perceptual beliefs to which we appeal for their justification.
 The argument that foundations must be certain was offered by Lewis (1946). He held that no proposition can be probable unless some are certain. If the probability of all propositions or beliefs were relative to evidence expressed in others, and if these relations were linear, then any regress would apparently have to terminate in propositions or beliefs that are certain. But Lewis shows neither that such relations must be linear nor that redresses cannot terminate in beliefs that are merely probable or justified in themselves without being certain or infallible.
 Arguments against the idea of the given originate with Kant (1724-1804), who argues that percepts without concepts do not yet constitute any form of knowing. Being non-epistemic, they presumably cannot serve as epistemic foundations. Once we recognize that we must apply concepts of properties to appearances and formulate beliefs utilizing those concepts before the appearances can play any epistemic role, it becomes more plausible that such beliefs are fallible. The argument was developed by Wilfrid Sellars (1963), which according to him, the idea of the given involves a confusion between sensing particulars (having sense impressions), which is non-epistemic, and having non-inferential knowledge of propositions referring to appearances. The former may be necessary for acquiring perceptual knowledge, but it is not itself a primitive kind of knowing. Its being non-epistemic renders it immune from error, but also unsuitable for epistemological foundations. The latter, non-referential perceptual knowledge, are fallible, requiring concepts acquired through trained responses to public physical objects.
 Contemporary foundationalists deny the coherentist’s claim whole eschewing the claim that foundations, in the form of reports about appearances, are infallible. They seek alternatives to the given as foundations. Although arguments against infallibility are sound, other objections to the idea of foundations are not. That concepts of objective properties are learned prior to concepts of appearances, for example, implied neither that claims about appearances are less certain than claims about objective properties, nor that the latter are prior in chains of justification. That there can be no knowledge prior to the acquisition and consistent application of concepts allows for propositions whose truth requires only consistent applications of concepts, and this may be so for some claims about appearances, least of mention, coherentists would add that such genuine belief’s stands in need of justification in themselves and so cannot be foundations.
 Until very recently it could have been that most approaches to the philosophy of science were ‘cognitive’. This includes ‘logical positivism’, as nearly all of those who wrote about the nature of science would have been in agreement that science ought to be ‘value-free’. This had been a particular emphasis on the part of the first positivist, as it would be upon twentieth-century successors. Science, so it is said, deals with ‘facts’, and facts and values and irreducibly distinct. Facts are objective.  They are what we seek in our knowledge of the world. Values are subjective: They bear the mark of human interest, they are the radically individual products of feeling and desire. Fact and value cannot, therefore, be inferred from fact, fact cannot be influenced by value. There were philosophers, notably some in the Kantian tradition, who viewed the relation of the human individual to the universalist aspiration of difference rather differently. But the legacy of three centuries of largely empiricist reflection of the ‘new’ sciences ushered in by Galilee Galileo (1564-1642), the Italian scientist whose distinction belongs to the history of physics and astronomy, rather than natural philosophy.
 The philosophical importance of Galileo’s science rests largely upon the following closely related achievements: (1) His stunning successful arguments against Aristotelean science, (2) his proofs that mathematics is applicable to the real world. (3) His conceptually powerful use of experiments, both actual and employed regulatively, (4) His treatment of causality, replacing appeal to hypothesized natural ends with a quest for efficient causes, and (5) his unwavering confidence in the new style of theorizing that would come to be known as ‘mechanical explanation’.
 A century later, the maxim that scientific knowledge is ‘value-laded’ seems almost as entrenched as its opposite was earlier. It is supposed that between fact and value has been breached, and philosophers of science seem quite at home with the thought that science and value may be closely intertwined after all. What has happened to bring about such an apparently radical change? What is its implications for the objectivity of science, the prized characteristic that, from Plato’s time onwards, has been assumed to set off real knowledge (epistēmē) from mere opinion (doxa)? To answer these questions adequately, one would first have to know something of the reasons behind the decline of logical positivism, as, well as of the diversity of the philosophies of science that have succeeded it.
 More general, the interdisciplinary field of cognitive science is burgeoning on several fronts. Contemporary philosophical re-election about the mind ~ which has been quite intensive ~ has been influenced by this empirical inquiry, to the extent that the boundary lines between them are blurred in places.
 Nonetheless, the philosophy of mind at its core remains a branch of metaphysics, traditionally conceived. Philosophers continue to debate foundational issues in terms not radically differently from those in vogue in previous eras. Many issues in the metaphysics of science hinge on the notion of ‘causation’. This notion is as important in science as it is in everyday thinking, and much scientific theorizing is concerned specifically to identify the ‘causes’ of various phenomena. However, there is little philosophical agreement on what it is to say that one event is the cause of some other.
 Modern discussion of causation starts with the Scottish philosopher, historian, and essayist David Hume (1711-76), who argued that causation is simply a matter for which he denies that we have innate ideas, that the causal relation is observably anything other than ‘constant conjunction’, that there are observable necessary connections anywhere, and that there is either an empirical or demonstrative proof for the assumptions that the future will resemble the past, and that every event has a cause. That is to say, that there is an irresolvable dispute between advocates of free-will and determinism, that extreme scepticism is coherent and that we can find the experiential source of our ideas of self-substance or God.
 According to Hume (1978) on event causes another if only if events of the type to which the first event belongs regularly occur in conjunctive events of the type to which the second event belongs. The formulation, however, leaves a number of questions open. Firstly, there is a problem of distinguishing genuine ‘causal law’ from ‘accidental regularities’. Not all regularities are sufficiently law-like to underpin causal relationships. Being that there is a screw in my desk could well be constantly conjoined with being made of copper, without its being true that these screws are made of copper because they are in my desk. Secondly, the idea of constant conjunction does not give a ‘direction’ to causation. Causes need to be distinguished from effects. But knowing that A-type events are constantly conjoined with B-type events does not tell us which of ‘A’ and ‘B’ is the cause and which the effect, since constant conjunction is itself a symmetric relation. Thirdly, there is a problem about ‘probabilistic causation’. When we say that causes and effects are constantly conjoined, do we mean that the effects are always found with the causes, or is it enough that the causes make the effect probable?
 Many philosophers of science during the past century have preferred to talk about ‘explanation’ than causation. According to the covering-law model of explanation, something is explained if it can be deduced from premises which include one or more laws. As applied to the explanation of particular events this implies that one particular event can be explained if it is linked by a law to some other particular event. However, while they are often treated as separate theories, the covering-law account of explanation is at bottom little more than a variant of Hume’s constant conjunction account of causation. This affinity shows up in the fact at the covering-law account faces essentially the same difficulties as Hume: (1) In appealing to deduction from ‘laws’, it needs to explain the difference between genuine laws and accidentally true regularities: (2) Its omission by effects, as well as effects by causes, after all, it is as easy to deduce the height of the flag-pole from the length of its shadow and the law of optics: (3) Are the laws invoked in explanation required to be exceptionalness and deterministic, or is it an acceptable say, to appeal to the merely probabilistic fact that smoking makes cancer more likely, in explaining why some particular person develops cancer?
 Nevertheless, one of the centrally obtainable achievements for which the philosophy of science is to provide explicit and systematic accounts of the theories and explanatory strategies exploitrated in the science. Another common goal is to construct philosophically illuminating analyses or explanations of central theoretical concepts invoked in one or another science. In the philosophy of biology, for example, there is a rich literature aimed at understanding teleological explanations, and there has been a great deal of work on the structure of evolutionary theory and on such crucial concepts as fitness and biological function. By introducing ‘teleological considerations’, this account views beliefs as states with biological purpose and analyses their truth conditions specifically as those conditions that they are biologically supposed to covary with.
 A teleological theory of representation needs to be supplemental with a philosophical account of biological representation, generally a selectionism account of biological purpose, according to which item ‘F’ has purpose ‘G’ if and only if it is now present as a result of past selection by some process which favoured items with ‘G’. So, a given belief type will have the purpose of covarying with ‘P’, say. If and only if some mechanism has selected it because it has covaried with ‘P’ the past.
 Along the same lines, teleological theory holds that ‘r’ represents ‘x’ if it is r’s function to indicate (i.e., covary with) ‘x’, teleological theories take issue depending on the theory of functions they import. Perhaps the most important distinction is that between historical theories of functions and a-historical theories. Historical theories individuate 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’ (physical states being a-historical) but lacking r’s historical origins would not represent ‘x’ according to historical theories.
 The American philosopher of mind (1935-) Jerry Alan Fodor, is known for resolute ‘realism’ about the nature of mental functioning, taking the analogy between thought and computation seriously. Fodor believes that mental representations should be conceived as individual states with their own identities and structures, like formulae transformed by processes of computation or thought. His views are frequently contrasted with those of ‘holist’ such as the American philosopher, Herbert Donald Davidson (1917-2003), or ‘instrumentalists’ about mental ascription, such as the British philosopher of logic and language, Eardley Anthony Michael Dummett, 1925- In recent years he has become a vocal critic of some of the aspirations of cognitive science.
 Nonetheless, a suggestion extrapolating the solution of teleology is continually queried by points as owing to ‘causation’ and ‘content’, and ultimately a fundamental appreciation is to be considered, is that: We suppose that there’s a causal path from A’s to ‘A’s’ and a causal path from B’s to ‘A’s’, and our problem is to find some difference between B-caused ‘A’s’ and A-caused ‘A’s’ in virtue of which the former but not the latter misrepresented. Perhaps, the two paths differ in their counter-factual properties. In particular, in spite of the fact that although A’s and B’s botheration gives cause by A’s’ every fragmentation is in pieces of its matter in the contestation of conveyance, and, as, perhaps, a conceivable assumption deducing that of only A’s would cause ‘A’s’ in ~ as one can say -, ‘optimal circumstances’. We could then hold that a symbol expresses its ‘optimal property’, viz., the property that would causally control its tokening in optimal circumstances. Correspondingly, when the tokening of a symbol is causally controlled by properties other than its optimal property, the tokens that eventuate are ipso facto wild.
 Suppose at the present time, that this story about ‘optimal circumstances’ is proposed as part of a naturalized semantics for mental representations. In which case it is, of course, essential that it be possible to say that the optimal circumstances for tokening a mental representation are in terms that are not themselves either semantical or intentional. (It would not do, for example, to identify the optimal circumstances for tokening a symbol as those in which the tokens are true, that would be to assume precisely the sort of semantical notion that the theory is supposed to naturalize.) Befittingly, the suggestion ~ to put it in a nutshell ~ is that appeals to ‘optimality’ should be buttressed by appeals to ‘teleology’: Optimal circumstances are the ones in which the mechanisms that mediate symbol tokening are functioning ‘as they are supposed to’. In the case of mental representations, these would be paradigmatically circumstances where the mechanisms of belief fixation are functioning as them are supposed to.
 So, then: The teleologies of the cognitive mechanisms determine the optimal condition for belief fixation, and the optimal condition for belief fixation determines the content of beliefs. So the story goes.
 To put this objection in slightly other words: The teleology story perhaps strikes one as plausible in that it understands one normative notion ~ truth ~ in terms of another normative notion ~ optimality. But this appearance if it is spurious there is no guarantee that the kind of optimality that teleology reconstructs has much to do with the kind of optimality that the explication of ‘truth’ requires. When mechanisms of repression are working ‘optimally’ ~ when they’re working ‘as they’re supposed to’ ~ what they deliver are likely to be ‘falsehoods’.
 Once, again, there’s no obvious reason why coitions that are optimal for the tokening of one sort of mental symbol need be optimal for the tokening of other sorts. Perhaps the optimal conditions for fixing beliefs about very large objects, are different from the optimal conditions for fixing beliefs about very small ones, are different from the optimal conditions for fixing beliefs sights. But this raises the possibility that if we’re to say which conditions are optimal for the fixation of a belief, we’ll have to know what the content of the belief is ~ what it’s a belief about. Our explication of content would then require a notion of optimality, whose explication in turn requires a notion of content, and the resulting pile would clearly be unstable.
 Teleological theories hold that ‘r’ represents ‘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: Historically, theories individuate 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’ (physical states being a-historical), but lacking r’s historical origins would not represent ‘x’ according to historical theories.
 Just as functional role theories hold that r’s representing ‘x’ is grounded in the functional role ‘r’ has in the representing system, i.e., on the relations imposed by specified 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 believe that cats are furry if they do not know that cats are animals or that fur is like hair.
 That being said, that nowhere is the new period of collaboration between philosophy and other disciplines more evident than in the new subject of cognitive science. Cognitive science from its very beginning has been ‘interdisciplinary’ in character, and is in effect the joint property of psychology, linguistics, philosophy, computer science and anthropology. There is, therefore, a great variety of different research projects within cognitive science, but the central area of cognitive science, its hard-coded ideology rests on the assumption that the mind is best viewed as analogous to a digital computer. The basic idea behind cognitive science is that recent developments in computer science and artificial intelligence have enormous importance for our conception of human beings. The basic inspiration for cognitive science went something like this: Human beings do information processing. Computers are designed precisely do information processing. Therefore, one way to study human cognition ~ perhaps the best way to study it ~ is to study it as a matter of computational information processing. Some cognitive scientists think that the computer is just a metaphor for the human mind: Others think that the mind is literally a computer program. But it is fair to say, that without the computational model there would not have been a cognitive science as we now understand it.
 In, Essay Concerning Human Understanding is the first modern systematic presentation of empiricist epistemology, and as such had important implications for the natural sciences and for philosophy of science generally. Like his predecessor, Descartes, the English philosopher (1632-1704) Walter Locke began his account of knowledge from the conscious mind aware of ideas. Unlike Descartes, however, he was concerned not to build a system based on certainty, but to identify the mind’s scope and limits. The premise upon which Locke built his account, including his account of the natural sciences, is that the ideas which furnish the mind are all derived from experience. He thus, totally rejected any kind of innate knowledge. In this he consciously opposing Descartes, who had argued that it is possible to come to knowledge of fundamental truths about the natural world through reason alone. Descartes (1596-1650) had argued, that we can come to know the essential nature of both the ‘mind’ and ‘matter’ by pure reason. Walter Locke accepted Descartes’s criterion of clear and distinct ideas as the basis for knowledge, but denied any source for them other than experience. It was information that came in a via the five senses (ideas of sensation) and ideas engendered from pure inner experiences (ideas of reflection) arose in the building blocks of the understanding.
 Locke combined his commitment to ‘the new way of ideas’ with the native espousal of the ‘corpuscular philosophy’ of the Irish scientist (1627-92) Robert Boyle. This, in essence, was an acceptance of a revised, more sophisticated account of matter and its properties that had been advocated by the ancient atomists and recently supported by Galileo (1564-1642) and Pierre Gassendi (1592-1655). Boyle argued from theory and experiment that there were powerful reasons to justify some kind of corpuscular account of matter and its properties. He called the latter qualities, which he distinguished as primary and secondary.  The distinction between primary and secondary qualities may be reached by two rather different routes: Either from the nature or essence of matter or from the nature and essence of experience, though practising these have tended to run together. The former considerations make the distinction seem like an a priori, or necessary, truth about the nature of matter, while the latter make it appears to be an empirical hypothesis -. Locke, too, accepted this account, arguing that the ideas we have of the primary qualities of bodies resemble those qualities as they are in the subject, whereas the ideas of the secondary qualities, such as colour, taste, and smell, do not resemble their causes in the object.
 There is no strong connection between acceptance of the primary secondary quality distinction and Locke’s empiricism and Descartes had also argued strongly for universal acceptance by natural philosophers, and Locke embraced it within his more comprehensive empirical philosophy. But Locke’ empiricism did have major implications for the natural sciences, as he well realized. His account begins with an analysis of experience. All ideas, he argues, are either simple or complex. Simple ideas are those like the red of a particular rose or the roundness of a snowball. Complicated and complex ideas, our ideas of the rose or the snowball, are combinations of simple ideas. We may create new complicated and complex ideas in our imagination ~ a parallelogram, for example. But simple ideas can never be created by us: We just have them or not, and characteristically they are caused, for example, the impact on our senses of rays of light or vibrations of sound in the air coming from a particular physical object. Since we cannot create simple ideas, and they are determined by our experience. Our knowledge is in a very strict uncompromising way limited. Besides, our experiences are always of the particular, never of the general. It is this particular simple idea or that particular complex idea that we apprehend. We never in that sense apprehend a universal truth about the natural world, but only particular instances. It follows from this that all claims to generality about that world ~ for example, all claims to identity what were then beginning to be called the laws of nature ~ must to that extent go beyond our experience and thus be less than certain.
 The Scottish philosopher, historian, and essayist, (1711-76) David Hume, whose famous discussion appears in both his major philosophical works, the ‘Treatise’ (1739) and the ‘Enquiry’(1777). The distinction is couched in terms of the concept of causality, so that where we are accustomed to talking of laws, Hume contends, involves three ideas:
  1. That there should be a regular concomitance between
  events of the type of the cause and those of the type
  of the effect.
  2. That the cause event should be contiguous with the
  affect events.
  3. That the cause event should necessitate the effect event.
The tenets (1) and (2) occasion no differently for Hume, since he believes that there are patterns of sensory impressions un-problematically related to the idea of regularity concomitance and of contiguity. But the third requirement is deeply problematic, in that the idea of necessarily that figures in it seems to have no sensory impression correlated with it. However, carefully and attentively we scrutinize a causal process, we do not seem to observe anything that might be the observed correlate of the idea of necessity. We do not observe any kind of activity, power, or necessitation. All we ever observe is one event following another, which is logically independent of it. Nor is this logical necessity, since, as, Hume observes, one can jointly assert the existence of the cause and a denial of the existence of the effect, as specified in the causal statement or the law of nature, without contradiction. What, then, are we to make of the seemingly central notion of necessity that is deeply embedded in the very idea of causation, or lawfulness? To this query, Hume gives an ingenious and telling story. There is an impression corresponding to the idea of causal necessity, but it is a psychological phenomenon: Our exception that even similar to those we have already observed to be correlated with the cause-type of events will come to be in this case too. Where does that impression come from? It is created as a kind of mental habit by the repeated experience of regular concomitance between events of the type of the effect and the occurring of events of the type of the cause. And then, the impression that corresponds to the idea of regular concomitance ~ the law of nature then asserts nothing but the existence of the regular concomitance.
 At this point in our narrative, the question at once arises as to whether this factor of life in nature, thus interpreted, corresponds to anything that we observe in nature. All philosophy is an endeavour to obtain a self-consistent understanding of things observed. Thus, its development is guided in two ways, one is demand for coherent self-consistency, and the other is the elucidation of things observed. With our direct observations how are we to conduct such comparisons? Should we turn to science? No. There is no way in which the scientific endeavour can detect the aliveness of things: Its methodology rules out the possibility of such a finding. On this point, the English mathematician and philosopher (1861-1947) Alfred Whitehead, comments: That science can find no individual enjoyment in nature, as science can find no creativity in nature, it finds mere rules of succession. These negations are true of natural science. They are inherent in its methodology. The reason for this blindness of physical science lies in the fact that such science only deals with half the evidence provided by human experience. It divides the seamless coat ~ or, to change the metaphor into a happier form, it examines the coat, which is superficial, and neglects the body which is fundamental.
 Whitehead claims that the methodology of science makes it blind to a fundamental aspect of reality, namely, the primacy of experience, it neglected half of the evidence. Working within Descartes’ dualistic framework reference, of matter and mind as separate and incommensurate, science limits itself to the study of objectivised phenomena, neglecting the subject and the mental events that are his or her experience.
 Both the adoption of the Cartesian paradigm and the neglect of mental events are reason enough to suspect ‘blindness’, but there is no need to rely on suspicions. This blindness is clearly evident. Scientific discoveries, impressive as they are, are fundamentally superficial. Science can express regularities observed in nature, but it cannot explain the reasons for their occurrence. Consider, for example, Newton’s law of gravity. It shows that such apparently disparate phenomena as the falling of an apple and the revolution of the earth around the sun are aspects of the same regularity ~ gravity. According to this law the gravitational attraction between two objects deceases in proportion to the square of the distance between them. Why is that so? Newton could not provide an answer. Simpler still, why does celestial or supernal space have three dimensions? Why is time one-dimensional? Whitehead notes, ‘None of these laws of nature gives the slightest evidence of necessity. They are [merely] the modes of procedure which within the scale of observation do in fact prevail’.
 This analysis reveals that the capacity of science to fathom the depths of reality is limited. For example, if reality is, in fact, made up of discrete units, and these units have the fundamental character in being ‘ the pulsing throbs of experience’, then science may be in a position to discover the discreteness: But it has no access to the subjective side of nature since, as the Austrian physicist(1887-1961) Erin Schrödinger points out, we ‘exclude the subject of cognizance from the domain of nature that we endeavour to understand’. It follows that in order to find ‘the elucidation of things observed’ in relation to the experiential or aliveness aspect, we cannot rely on science, we need to look elsewhere.
 If, instead of relying on science, we rely on our immediate observation of nature and of ourselves, we find, first, that this [i.e., Descartes’] stark division between mentality and nature has no ground in our fundamental observation. We find ourselves living within nature. Secondly, in that we should conceive mental operations as among the factors which make up the constitution of nature, and thirdly, that we should reject the notion of idle wheels in the process of nature. Every factor which makes a difference, and that difference can only be expressed in terms of the individual character of that factor.
 Whitehead proceeds to analyse our experiences in general, and our observations of nature in particular, and ends up with ‘mutual immanence’ as a central theme. This mutual immanence is obvious in the case of an experience that, I am a part of the universe, and, since I experience the universe, the experienced universe is part of me. Whitehead gives an example, ‘I am in the room, and the room is an item in my present experience. But my present experience is what I am now’. A generalization of this relationship to the case of any actual occasions yields the conclusion that ‘the world is included within the occasion in one sense, and the occasion is included in the world in another sense’. The idea that each actual occasion appropriates its universe follows naturally from such considerations.
 The description of an actual entity for being a distinct unit is, therefore, only one part of the story. The other, complementary part is this: The very nature of each and every actual entity is one of interdependence with all the other actual entities in the universe. Each and every effective entity the determinant by which some outward appearance of something as distinguished from the substance for which it is made a process of prehending or appropriating all the other actual entities and creating one new entity out of them all, namely, itself.
 There are two general strategies for distinguishing laws from accidentally true generalizations. The first stands by Hume’s idea that causal connections are mere constant conjunctions, and then seeks to explain why some constant conjunctions are better than others. That is, this first strategy accepts the principle that causation involves nothing more than certain events always happening together with certain others, and then seeks to explain why some such patterns ~ the ‘laws’ ~ matter more than others ~ the ‘accidents’ -. The second strategy, by contrast, rejects the Humean presupposition that causation involves nothing more than is responsible for an effect to happen in reserve to the chance-stantial co-occurrence, and instead postulates the relationship ‘necessitation’, a kind of ‘cement, which links events that are connected by law, but not those events (like having a screw in my desk and being made of copper) that are only accidentally conjoined.
 There are a number of versions of the first Human strategy. The most successful, originally proposed by the Cambridge mathematician and philosopher F.P. Ramsey (1903-30), and later revived by the American philosopher David Lewis (1941-2002), who holds that laws are those true generalizations that can be fitted into an ideal system of knowledge. The thought is, that, the laws are those patterns that are somewhat explicated in terms of basic science, either as fundamental principles themselves, or as consequences of those principles, while accidents, although true, have no such explanation. Thus, ‘All water at standard pressure boils at 1000 C’ is a consequence of the laws governing molecular bonding: But the fact that ‘All the screws in my desk are copper’ is not part of the deductive structure of any satisfactory science. Frank Plumpton Ramsey (1903-30), neatly encapsulated this idea by saying that laws are ‘consequences of those propositions which we should take as axioms if we knew everything and organized it as simply as possible in a deductive system’.
 Advocates of the alternative non-Humean strategy object that the difference between laws and accidents is not a ‘linguistic’ matter of deductive systematization, but rather a ‘metaphysical’ contrast between the kind of links they report. They argue that there is a link in nature between being at 1000 C and boiling, but not between being ‘in my desk’ and being ‘made of copper’, and that this is nothing to do with how the description of this link may fit into theories. According to the forthright Australian D.M. Armstrong (1983), the most prominent defender of this view, the real difference between laws and accidentals, is simply that laws report relationships of natural ‘necessitation’, while accidents only report that two types of events happen to occur together.
 Armstrong’s view may seem intuitively plausible, but it is arguable that the notion of necessitation simply restates the problem, than solving it. Armstrong says that necessitation involves something more than constant conjunction: If two events e related by necessitation, then it follows that they are constantly conjoined, but two events can be constantly conjoined without being related by necessitation, as when the constant conjunction is just a matter of accidents. So necessitation is a stronger relationship than constant conjunction. However, Armstrong and other defenders of this view say very little about what this extra strength amounts to, except that it distinguishes laws from accidents. Armstrong’s critics argue that a satisfactory account of laws ought to cast more light than this on the nature of laws.
 Hume said that the earlier of two causally related events is always the cause, and the later effect. However, there are a number of objections to using the earlier-later ‘arow of time’ to analyse the directional ‘arrow of causation’. For a start, it seems in principle, possible that some causes and effects could be simultaneous. That more, in the idea that time is directed from ‘earlier’ too ‘later’ itself stands in need of philosophical explanation ~ and one of the most popular explanations is that the idea of ‘movement’ from earlier to later depend on the fact that cause-effect pairs always have a time, and explain ‘earlier’ as the direction in which causes lie, and ‘later’ as the direction of effects, that we will clearly need to find some account of the direction of causation which does not itself assume the direction of time.
 A number of such accounts have been proposed. David Lewis (1979) has argued that the asymmetry of causation derives from an ‘asymmetry of over-determination’. The over-determination of present events by past events ~ consider a person who dies after simultaneously being shot and struck by lightning ~ is a very rare occurrence, by contrast, the multiple ‘over-determination’ of present events by future events is absolutely normal. This is because the future, unlike the past, will always contain multiple traces of any present event. To use Lewis’s example, when the president presses the red button in the White House, the future effects do not only include the dispatch of nuclear missiles, but also the fingerprint on the button, his trembling, the further depletion of his gin bottle, the recording of the button’s click on tape, he emission of light waves bearing the image of his action through the window, the warnings of the wave from the passage often signal current, and so on, and so on, and on.
  The American philosopher David Lewis (1941-2002), relates this asymmetry of over-determination to the asymmetry of causation as follows. If we suppose the cause of a given effect to have been absent, then this implies the effect would have been absent too, since (apart from freak -like occurrence in the lightning-shooting case) there will not be any other causes left to ‘fix’ the effect. By contrast, if we suppose a given effect of some cause to have been absent, this does not imply the cause would have been absent, for there are still all the other traces left to ‘fix’ the causes. Lewis argues that these counterfactual considerations suffice to show why causes are different from effects.
 Other philosophers appeal to a probabilistic variant of Lewis’s asymmetry. Following, the philosopher of science and probability theorists, Hans Reichenbach (1891-1953), they note that the different causes of any given type of effect are normally probabilistically independent of each other, by contrast, the different effects of any given type of cause are normally probabilistically correlated. For example, both obesity and high excitement can cause heart attacks, but this does not imply that fat people are more likely to get excited than thin ones: Its facts, that both lung cancer and nicotine-stained fingers can result from smoking does imply that lung cancer is more likely among people with nicotine-stained fingers. So this account distinguishes effects from causes by the fact that the former, but not the latter are probabilistically dependent on each other.
 However, there is another course of thought in philosophy of science, the tradition of ‘negative’ or ‘eliminative’ induction. From the English statesman and philosopher Francis Bacon (1561-1626) and in modern time the philosopher of science Karl Raimund Popper (1902-1994), we have the idea of using logic to bring falsifying evidence to bear on hypotheses about what must universally be the case that many thinkers accept in essence his solution to the problem of demarcating proper science from its imitators, namely that the former results in genuinely falsifiable theories whereas the latter do not. Although falsely, allowed many people’s objections to such ideologies as psychoanalysis and Marxism.