Consciousness

Philosophers have used the term ‘consciousness' for four main topics: knowledge in general, intentionality, introspection (and the knowledge it specifically generates) and phenomenal experience. This entry discusses the last two uses. Something within one's mind is ‘introspectively conscious' just in case one introspects it (or is poised to do so). Introspection is often thought to deliver one's primary knowledge of one's mental life. An experience or other mental entity is ‘phenomenally conscious' just in case there is ‘something it is like' for one to have it. The clearest examples are: perceptual experiences, such as tastings and seeings; bodily-sensational experiences, such as those of pains, tickles and itches; imaginative experiences, such as those of one's own actions or perceptions; and streams of thought, as in the experience of thinking ‘in words' or ‘in images'. Introspection and phenomenality seem independent, or dissociable, although this is controversial. Phenomenally conscious experiences have been argued to be nonphysical, or at least inexplicable in the manner of other physical entities. Several such arguments allege that phenomenal experience is ‘subjective'; that understanding some experiences requires undergoing them (or their components). The claim is that any objective physical science would leave an ‘explanatory gap', failing to describe what it is like to have a particular experience and failing to explain why there are phenomenal experiences at all. From this, some philosophers infer ‘dualism' rather than ‘physicalism' about consciousness, concluding that some facts about consciousness are not wholly constituted by physical facts. This dualist conclusion threatens claims that phenomenal consciousness has causal power, and that it is knowable in others and in oneself. In reaction, surprisingly much can be said in favour of ‘eliminativism' about phenomenal consciousness; the denial of any realm of phenomenal objects and properties of experience. Most (but not all) philosophers deny that there are phenomenal objects - mental images with colour and shape, pain-objects that throb or burn, inner speech with pitch and rhythm, and so on. Instead, experiences may simply seem to involve such objects. The central disagreement concerns whether these experiences have phenomenal properties - ‘qualia'; particular aspects of what experiences are like for their bearers. Some philosophers deny that there are phenomenal properties - especially if these are thought to be intrinsic, completely and immediately introspectible, ineffable, subjective or otherwise potentially difficult to explain on physicalist theories. More commonly, philosophers acknowledge qualia of experiences, either articulating less bold conceptions of qualia, or defending dualism about boldly conceived qualia. Introspective consciousness has seemed less puzzling than phenomenal consciousness. Most thinkers agree that introspection is far from complete about the mind and far from infallible. Perhaps the most familiar account of introspection is that, in addition to ‘outwardly perceiving' non-mental entities in one's environment and body, one ‘inwardly perceives' one's mental entities, as when one seems to see visual images with one's ‘mind's eye'. This view faces several serious objections. Rival views of introspective consciousness fall into three categories, according to whether they treat introspective access (1) as epistemically looser or less direct than inner perception, (2) as tighter or more direct, or (3) as fundamentally non-epistemic or nonrepresentational. Theories in category (1) explain introspection as always retrospective, or as typically based on self-directed theoretical inferences. Rivals from category (2) maintain that an introspectively conscious mental state reflexively represents itself, or treat introspection as involving no mechanism of access at all. Category (3) theories treat a mental state as introspectively conscious if it is distinctively available for linguistic or rational processing, even if it is not itself perceived or otherwise thought about. 1 Pre-Cartesian uses of ‘consciousness' As elsewhere in philosophy, Descartes' writings mark a major shift in philosophical preoccupation with consciousness. Pre-Cartesian philosophers of mind rarely emphasize the terms ‘conscious' or ‘consciousness' (or clear equivalents). Post-Cartesian philosophers of mind rarely avoid such emphasis. This section compares Descartes' usage with earlier usage. Descartes typically speaks of being ‘conscious' to refer to an allegedly intimate source of knowledge about one's own mental occurrences. In the ‘Conversation with Burman' he says that ‘to be conscious is both to think and to reflect on one's thought' (1648: 335), where the term ‘thought' extends widely, as in the ‘Second Replies', to ‘everything that is within us in such a way that we are immediately conscious of it' including ‘all the operations of the will, the intellect, the imagination and the senses' (1641: 113). Descartes seems to treat everything mental as introspectively conscious, in these passages and elsewhere ( the ‘Fourth Replies', 1641: 171). Elsewhere, however, Descartes seems to deny that introspection is complete, as in the Discourse on Method: ‘many people do not know what they believe, since believing something and knowing that one believes it are different acts of thinking, and the one often occurs without the other'. The resulting focus on the scope and limits of introspective knowledge ( §§6-7) is apparently responsible for the modern uses of ‘conscious' and ‘non-conscious' to mark a potential distinction between two kinds of mental states. Introspected states are (introspectively) conscious, while others, if any, are (introspectively) unconscious. Pre-Cartesian authors do not use the word ‘conscious' to mark such a distinction, although some may be committed to the distinction, either implicitly or in other terms (Whyte 1962). To take a rather spectacular example, Socrates claims in Plato's Meno that since one's soul ‘has been born many times' and ‘has learned everything that there is', ‘seeking and learning are in fact nothing but recollection' (81c-d). This seems to require that one has latent knowledge of which one can at best become aware with great difficulty ( Plato §11). Many pre-Cartesian writers share commitment to a special fountain of reflective knowledge, often called ‘inner sense'. In Summa theologiae Aquinas posits a ‘common sense' which enables one, for example, to ‘tell white from sweet', and adds that this common sense ‘is also able to sense sensation itself, as when somebody sees that he is seeing' (I.78.4). This responds to Aristotle's apparent claim, in On the Soul, that it is ‘by sight that one perceives that one sees' rather than by another sense (III 2, 425b12). On these views, the subject matter of such inner awareness is more restricted than for Descartes, including sensation but perhaps not other mental processes. It may even be that, for Aristotle, the relevant ‘inner' perception - by which one sees that one sees - is directed at one's external sense organs themselves and not at anything Descartes would consider strictly ‘mental'. A nearer equivalent to ‘introspective consciousness' is the Sanskrit term ‘manas', used widely in Hindu texts for a ‘mind-organ' that functions like the external sense organs. For instance, the Vai?e????ika S?tra (c. 3rd century BC) claims that ‘Intellect, pleasure, pain, desire, aversion, effort are perceptible by the internal organ'. This inner perception is carefully distinguished from ‘inferential knowledge', and is framed so as not to involve introspection of a ‘self'. Indeed, while Descartes holds that he can introspect himself as a ‘thinking thing', Hinduism characteristically claims that introspection reveals no ‘true self' distinct from one's mental states, and Buddhism characteristically denies that there are ‘thinking things' at all. The word ‘conscious' derives from the Latin words ‘cum' (‘together with') and ‘scire' (‘knowing'). In the original sense, two people who know something together are said to be conscious of it ‘to one another', with the irresistible connotation that they are privy to a scandalous secret. By extension, one can be conscious ‘to oneself' of secret shames - whence the original use of ‘consciousness' for conscience, the inner accuser silently sharing knowledge of one's transgressions. This archaic moral sense of ‘consciousness' is not a concern in this entry. The Latin conjunction of ‘cum' and ‘scire' also has a use in which the prefix is merely emphatic, so that being ‘conscious of' something simply means knowing it, or knowing it well. In this sense the word ‘conscious' can also be used as an adjective: a ‘knowing' being such as a normal person is a conscious being, while an ‘unknowing' being such as a plant or sleeping person is an unconscious being. ‘Conscious', like ‘knowing', can be used in this way for things with minds but not for things within minds, such as mental states. People and animals know things - are conscious of things - but mental states do not themselves know things. Thus, for example, Aquinas uses ‘conscious' to describe bearers of mental states - such as human beings, animals and God - but not to describe mental states - not even ‘seen' seeings. Since the main philosophical problems about consciousness concern the more modern distinction between conscious and unconscious states, this entry focuses neither on the distinction between conscious and unconscious subjects, nor on the broad ‘knowing' sense of ‘conscious' ( Knowledge, concept of). In effect, Descartes refashions the ‘knowing well' sense of ‘conscious', regimenting it for a particular source of knowing, introspection. Issues about the specific epistemological status of introspection are a central concern of this entry. 2 Post-Cartesian uses of ‘consciousness' Descartes' use of ‘consciousness' for reflective knowledge spread rapidly through the next generation of European philosophers. In An Essay concerning Human Understanding Locke writes, as he does of ‘reflection', that ‘Consciousness is the perception of what passes in a Man's own mind' (1689: II.i.19); Leibniz's term for this is ‘apperception'. In his Critique of Pure Reason Kant goes on to distinguish between ‘empirical apperception' of a ‘flux of inner appearances' - mentioning that ‘Such consciousness is usually named inner sense' - and ‘transcendental apperception' which is alleged to be a ‘pure original unchangeable consciousness' that reveals a ‘fixed and abiding self' (A107; see Kant, I. §6). This entry discusses one's introspective access to the ‘flux' of particular events within one's mind, rather than substantive introspective knowledge about one's self - about whether one is made of physical or spiritual components, and whether one persists through time. In the broader ‘knowing' sense ( §1), a creature is conscious of something just in case it knows something, independently of whether this knowing is itself introspectible. This ancient sense of ‘conscious' lingers on, and broadens to cover any kind of belief or cognition (whether or not it is ‘knowledge'), and any kind of attitude about something (whether or not it is ‘cognitive'). In this sense, a creature has consciousness if it has any kind of ‘intentional' mental state. By extension, the state itself can be said to be a state of consciousness, even if it is not introspectible. (This is distinct from the widespread claim that all conscious states are intentional - that ‘all consciousness…is consciousness of something' (Sartre 1943: 11). On this broad sense of ‘conscious', by definition, all ‘ofness' is conscious ofness.) As twentieth-century philosophers of mind and language most often pursue concerns about intentionality using terms other than ‘consciousness', intentionality will not be explored in this entry. In a still broader sense, ‘mind' and ‘consciousness' are synonyms, as are ‘being mindful of' something and ‘being conscious of' it, so that any kind of mental state (whether or not it is an ‘attitude') is a state of consciousness. When Hegel (§5), Marx or Lukács speak of ‘unhappy', ‘false' or ‘class' consciousness, or when political activists attempt to ‘raise' consciousness, their concerns are usually equally well rendered using a general term such as ‘knowledge', ‘thinking', ‘attitudes' or ‘mentality' in place of ‘consciousness'. It is not clear that their concern is with introspection, since they refer mainly to thoughts about (or seemingly about) non-mental things, independently of whether these thoughts are themselves introspectively conscious. (When Hegel refers to thoughts explicitly about the mind, he uses ‘self-consciousness' rather than ‘consciousness'.) Likewise, many scientific writings officially on ‘consciousness' are about mentation and mentation-like activity in general, avoiding any question of whether the activity is introspectively conscious. Since these broad uses of ‘consciousness' seem to introduce no distinctive philosophical perplexities, this entry puts them aside. With the dawn of scientific psychology in the late nineteenth century, the central philosophical controversies about consciousness centre around whether consciousness can ever be explained by an objective science of the mind. The biologist Thomas Huxley provides an early attempt to express the sense of mystery: ‘How it is that anything so remarkable as a state of consciousness comes about as a result of irritating nervous tissue, is just as unaccountable as the appearance of Djin when Aladdin rubbed his lamp' (1866: 210). Since that time there have been many scientific advances in understanding the mechanisms of perception, thought and communication, and many philosophical advances in understanding the nature of intentionality and meaning. According to Thomas Nagel and many other philosophers, such advances must leave an unexplained residue, concerning what it is like to have phenomenally conscious experiences (as illustrated in the introduction; see Nagel, T. §4). Nagel writes that ‘Consciousness is what makes the mind-body problem really intractable', identifying ‘subjectivity' as its most troublesome feature: Fundamentally an organism has conscious mental states if and only if there is something it is like to be that organism - something it is like for the organism. We may call this the subjective character of experience…every subjective phenomenon is essentially connected with a single point of view, and it seems inevitable that an objective, physical theory will abandon that point of view. (1974: 166-7) Until quite recently, the agenda for the philosophy of mind has been set more by epistemology than by the sciences of mind. Consequently, introspective consciousness has been the most central and important philosophical notion of consciousness. The remainder of the entry is divided between the explanation of phenomenal consciousness and the epistemology of introspective consciousness. 3 Subjectivity and the phenomenal Nagel argues that physical theories cannot explain one's phenomenal consciousness, because they abandon one's point of view ( §2). Science does indeed abandon one's point of view, in so far as one need not be able to understand or defend the theory (if one lacks relevant concepts or evidence), and in so far as subjects with other points of view should be able to understand and defend the theory. But does abandoning a point of view prevent describing the point of view, or the features viewed from that point? Even if Nagel is correct that one's point of view and one's phenomenal experience are ‘essentially' connected, they may not be exclusively connected. An objective physical theory of phenomenal consciousness would presumably allow that phenomenal features are accessible from multiple points of view - for instance, both by some form of introspection and by some form of neurophysiological or psychological observation and theory. Furthermore, if experiences are necessarily introspectible or introspected ( §6) this might explain Nagel's claim that phenomenal features are ‘essentially connected with a single point of view'. Frank Jackson (1982) amplifies Nagel's challenge in his ‘knowledge argument' against ‘physicalism', the thesis that the world is wholly physical. He imagines a super-scientist, Mary, who has never seen anything coloured because she lives her life in a black-and-white room. From a black-and-white television in this room, she learns all the objectively specifiable physical (and causal or ‘functional') facts in the world. When she finally leaves the room and first sees colour, Jackson argues, she learns a new fact about the nature of phenomenal experience; she might exclaim, ‘Oh! It is like this to see red!' The new fact Mary learns cannot be identical to a physical or functional fact, or else it would be among the facts Mary already knows before leaving the room. So no wholly physicalist account of phenomenal facts can be true. Most responses to Jackson's argument involve denying that Mary learns a new fact upon experiencing red. On some views, she learns how to do new things - to imagine experiencing redness or to recognize redness visually - without coming to know that any new fact obtains. On others, she learns that an old physical fact about experience obtains, but comes to know it in a new way - via introspective access or via new concepts. For example, one proposal (Lycan 1990) compares the relevant introspective ways of representing one's experiences with simple inner-perceptual demonstratives, ways of knowing colour experience that would be unavailable to Mary from within the black-and-white room. Consider an analogy: when one perceives a banana and thinks of it demonstratively - as ‘this' - those who do not perceive the banana cannot think of it in the same way - simply as ‘this' (while staring at something else). Likewise, if one's introspections of one's experiences involve some demonstratives of them, this would explain why these representations cannot strictly be shared by someone who does not ‘perceive' the same experiences but merely thinks about them. Even among philosophers who accept that phenomenal consciousness is some physical or functional process, there are doubts about the possibility of explaining it. Colin McGinn (1991) suggests that human beings are forever blocked from knowing the ‘link' between the brain and consciousness, roughly because introspective consciousness gives no knowledge of brains, while neuroscientific access to brains gives no access to consciousness. Critics respond that one might learn the explanatory link by theoretical inference from joint introspective and scientific data, such as correlations between phenomenal features and brain states ( Flanagan 1992: ch. 6). In slightly different ways, Jackson, Joseph Levine (1993) and David Chalmers (1996) argue that even if one can know what this ‘link' in fact is, explanations based upon it cannot be as satisfying as other scientific explanations. In essence, the argument is that for any objective, scientific account of phenomenal consciousness, one can conceive of a creature that meets the conditions in the account but lacks phenomenal consciousness. In the extreme case, it is said, one can conceive of a world that is an exact physical duplicate of the actual world - complete with duplicate stars, planets, rocks, plants, animals and philosophers - but which lacks any phenomenal consciousness. All the human-like beings in that world would be non-phenomenal ‘zombies'. So the prescientific concept of phenomenal consciousness is not such that scientific premises could necessitate, a priori, conclusions about the phenomenal. In Levine's terms, there is an ‘explanatory gap' between physical reality and phenomenal consciousness. By contrast, for example, it is claimed that the prescientific concept of ‘water' is such that scientific premises about H2O, can necessitate, a priori, conclusions about water. In particular, it is held to be part of our concept of water that if there is anything roughly unique in the lakes and rivers around us that has a preponderance of features such as boiling, eroding rocks, quenching thirst and so on, then it is water. If science establishes that H2O meets this condition, then there is no further conceptual possibility that H2O is not water. At least three lines of response may be advanced against the explanatory gap argument. One concedes that no scientific premises a priori necessitate conclusions about the phenomenal, but insists that the same is true for scientific explanations of water, and so on. Perhaps someone who believes in water but denies that it boils, is in lakes and so on is making a false and bizarre claim but are not strictly contradicting themselves. The fate of this response presumably depends on the fate of general reservations about a priori or conceptual necessity. The second strategy also concedes the lack of a priori necessity, but attributes it to the idiosyncratic ways in which phenomenal facts are represented - for example, by introspection-based demonstratives ( Tye 1995: 178-81; Demonstratives and indexicals). By comparison, suppose that agent A holds banana B in front of his face, and comes to accept the demonstrative ‘This is a banana'. This conclusion cannot strictly be deduced from any demonstrative-free descriptions of the banana - that B is a banana in A's hand, that A sees B, and so on. The subject could believe all of these premises, and still conceive that this is not a banana - perhaps by conceiving that he is not in fact agent A. This response to the explanatory gap seems at best to apply only to particular phenomenal conclusions, of the form: it is like this to have a given experience. It is an incomplete response, since there are phenomenal conclusions without demonstratives, namely, those of the form: there is something it is like to have a given experience. The third strategy is to deny that there is an unbridgeable conceptual gap; in effect, to deny that zombies (non-phenomenal physical duplicates of phenomenal creatures) are even conceptually possible. In Nagel-like fashion, Robert Kirk analyses the concept of phenomenality as follows: a creature's phenomenal states are those with different ‘characters' that are ‘for the creature as a whole' (1994: ch. 5). He explains this in terms of neural states with different ‘patterns of activation' that are ‘directly available' to ‘have different effects on processes of assessment, decision-making, and action initiation'. It follows that if a creature has states with characters for the creature, any physical duplicate of the creature does also. The problem is that Kirk's ‘having character' does not express the same concept as Nagel's ‘being like something'. Perhaps Kirk demonstrates how states can be ‘for a creature', but he does not demonstrate that they are ‘like something' for the creature, that is, phenomenal, in Nagel's full-blown sense. For example, beliefs may also be realized in different patterns of activation with the relevant direct availability, and so in that sense beliefs may be ‘for' a creature, but beliefs are not clearly themselves ‘like something' for a creature ( §6). Further analysis of the ‘like something' idiom would be needed to complete this line of response to the explanatory gap. 4 Dualism and the phenomenal The attraction of subjectivity-based arguments against physicalism makes it important to understand the potential ramifications of various non-physicalist alternatives. The central metaphysical issues concern ‘mental causation' and ‘emergence' ( Mental causation). The two central epistemological ramifications concern knowledge of other minds and knowledge of one's own mind ( Other Minds). Physical science promises an explanation of physical events wholly in terms of other physical events. For example, unsupported objects fall, not because they want to fall, but because of gravitational forces. Similarly, a large group of neurons cause another neuron to fire, not because of its embarrassment due to peer pressure or its fear of a mob, but because of electrochemical forces. In this way, there should be a purely physical explanation of the activities of brains in producing (reflex or non-reflex) behaviour. Yet phenomenal consciousness also seems to have physical consequences on behaviour. When one feels an itch, one scratches; this seems to be in large part because of what it is like to itch. But how can an itchy feel make a difference, if there is a purely physical explanation of one's hand motions? The physicalist may make room for phenomenal causation by maintaining that the feel of an itch is wholly constituted by (or, perhaps, identical with) features of the brain and body ( Mind, identity theory of). The feel causes the hand motion, because it is made of things that do so, just as the brain causes the hand motion by being composed of things that do so (that is, neurons). But this strategy is unavailable to the non-physicalist who thinks there are mental objects, properties or states that are not wholly composed of physical entities ( Dualism). One possibility for the dualist is to maintain that some physical events are inexplicable purely in physical terms - this is Descartes' own position about non-reflex behaviour. Another prominent strategy is to defend ‘epiphenomenalism' about the phenomenal, or the idea that, contrary to appearances, phenomenal features are irrelevant to the generation of physical events ( Jackson 1982; Chalmers 1996: ch. 4; Epiphenominalism). If phenomenal states and features are not wholly constituted by physical states and features, how are they constituted? One idea, prevalent among neuroscientists, is that the phenomenal ‘emerges' from physical interactions. By analogy, water has properties that are not explicable by the properties of hydrogen and oxygen separately. Water dissolves salt, but neither hydrogen nor oxygen does so separately (nor does hydrogen dissolve part of salt and oxygen the rest). Analogously, the whole of a phenomenal experience is taken to be more than the sum of its physical parts (that is, the physical entities that help realize it). The initial plausibility of such analogies seems to depend on a too-narrow conception of the ‘parts' of a complex entity. A water molecule does have hydrogen and oxygen atoms as parts, but it also has various relations among these atoms as other ‘parts'. The physical relation of bonding, for instance, is as necessary for water as the atoms are. If all of the parts of water are counted, it is not clear that water has properties inexplicable by the properties of these parts. This kind of ‘emergence' conclusion - one that forgets to ‘sum' some of the parts of a whole - is compatible with a wholly physicalist account of water, and of consciousness. In the absence of better analogies, non-physicalist philosophers have more commonly denied that there is genuine emergence, emergence of new features that are inexplicable in terms of combinations of other features. This leads some non-physicalists to the startling ‘panpsychist' claim that mental ‘ingredients' of phenomenal consciousness must be present in the tiniest bits of matter capable of comprising brains, and to the claim that phenomenal consciousness is a fundamental part of nature - perhaps along with subatomic mass and charge. Epiphenomenalism and panpsychism exacerbate the epistemological problem of other minds, but in opposite directions. It seems that we have excellent, even if not quite perfect, justification for believing that other people have experiences. Plausibly, talk of experiences is not simply disguised talk of others' observable behaviour, but is instead to be inferred from behaviour with some degree of theoretical risk. Perhaps the inference is in part grounded on drawing an analogy between oneself and others, but inference from a single case gives one at best meagre justification for conclusions about others. The residual problem of other minds, then, is to explain how one attains an appropriate level of justification. The physicalist can maintain that one is justified in part because the phenomenal features of experience help explain behaviour - in fact, help cause it. But the epiphenomenalist seems forced to deny this, potentially rendering it too hard to attain knowledge of other minds. The panpsychist, on the other hand, renders it too easy to attain such knowledge; not only other people but other animals, plants, rocks and protons have mental features. A final danger with the idea that phenomenal consciousness depends on nonphysical features is that it threatens self-knowledge about one's phenomenal states. The nonphysicalist who believes that zombies are possible believes that two people could be alike in all non-phenomenal respects, while one has phenomenal experience and the other does not. Each could be fully convinced of their own rich, detailed phenomenal experience, but one would be wrong. It is difficult to see how either could justify their belief that they are not a zombie, if zombies are possible. Chalmers tries to address this problem by stipulating that non-zombies are necessarily distinctively justified: To have an experience is automatically to stand in some sort of intimate epistemic relation to the experience - a relation that we might call ‘acquaintance.' There is not even a conceptual possibility that a subject could have a red experience like this one without having any epistemic contact with it: to have the experience is to be related to it in this way…. [This] is to stand in a relationship to it more primitive than belief: it provides evidence for our beliefs, but it does not in itself constitute belief. (1996: 196-7) This conclusion anticipates the idea that inner perceptions of one's experiences - taken to be more ‘primitive' than reflective beliefs about one's experiences - are necessary for phenomenal consciousness ( §6). But where the non-zombie has inner perceptual states, by hypothesis the zombie has them also. Perhaps what zombies have are misperceptions, but this need not lessen their justification in accepting these misperceptions at face value, and in believing they have experiences. Also, the heavy reliance on introspections of experience opens up two alternatives for physicalism. The first is to deny that there is experience at all, but only the favoured kind of introspections as of experience. The second - perhaps the more attractive - is to maintain that the favoured kind of introspections are sufficient for experience. This is to invert Chalmers' claim that ‘to have the experience is to be related to it in this [inner perceptual] way'; if so, this is precisely because to be related to a state in this inner perceptual way is to have an experience. Neither strategy carries obvious commitment to anything nonphysical. (For related objections to ‘absent qualia', see Shoemaker (1984: chaps 9, 14); and for a response, see Block (1980). Rey (1986) extends the point, arguing that non-psychological requirements on phenomenal consciousness - perhaps biological or neurophysiological ones - would also jeopardize introspective knowledge of experience; see also Chalmers (1996: 7).) 5 Eliminativism and the phenomenal In addition to subjectivity-based arguments, phenomenally conscious experiences provide other interesting arguments against physicalism. In certain experiences one seems to be aware of phenomenal denizens of an inner mental world: coloured and shaped mental ‘images', bodily ‘sensations' such as ‘pains' that may be throbbing or in one's limb, and inner ‘speech' with ‘private' volume and pitch. Such alleged mental objects as afterimages, pains and inner speeches, that are naturally reported as having properties of non-mental objects (for example, roundness, throbbingness or loudness), may be called ‘phenomenal objects'. The argument against physicalism based on reports of phenomenal objects is simple. In such experiences nothing in one's brain or body or (causally relevant) environment is literally purple and round, literally throbbing and in a limb, or literally soft and medium-pitched. So if phenomenal objects do exist with these properties, they are not among the things in one's brain or body or environment. One must be either a dualist ( §4) or an ‘eliminativist' about mental entities with these properties; that is, the physicalist must deny that objects with such properties exist ( Eliminativism). The challenge for the eliminativist about phenomenal objects is to explain why people are often tempted to claims of phenomenal objects, with ordinary perceptible properties. Broadly, the temptation may be attributed to an ambiguity or looseness in ordinary reports of experiences, or to an illusion built into the experiences themselves, which may then be reported strictly and faithfully. Following a suggestion due to Ned Block, Michael Tye (1995) pursues the former strategy by pointing out that people often describe representations as having properties that they merely represent: the phrase ‘a warm thermostat setting' may be used for a thermostat setting of warmth, and ‘a nude painting' may be used for a painting of nudity. It should be no surprise then that people describe experiences of colour and shape as themselves being coloured and shaped, and so no surprise that, speaking freely, they treat them as images. The other strategy is latent in J.J.C. Smart's suggestion that ‘There is, in a sense, no such thing as an after-image…though there is such a thing as the experience of having an image' (1959: 151). On one straightforward construal of ‘the experience of having an image', an experience itself represents that there is an image with certain features, although there is no such thing (compare with Sartre's ‘illusion of immanence', 1940: 5). The illusory-experience view has an advantage over the reporting-based view to the extent that afterimages look purple and round, pains feel dull or in motion, and inner speech seems to sound faint or high-pitched. By contrast, a warm thermostat setting need not itself feel warm, and a nude painting need not itself look nude (any more than other paintings look clothed). However, without an account of why experiences misrepresent phenomenal objects, the illusory-experience view does not adequately discharge the eliminativist's explanatory burden. In addition to phenomenal objects, eliminativists have targeted alleged ‘phenomenal properties' of experiences, or ‘qualia'. There is not merely ‘something' it is like to have a phenomenally conscious experience, but some particular ‘thing' or things it is like. People sometimes try to describe these particular properties, for example, by saying that a given pain is ‘sharp' or ‘throbbing' to some degree, or that a given visual image is ‘blurry' or ‘moving'. Even if the eliminativist about phenomenal objects is correct that there are only experiences as of sharp throbbing pains and as of blurry moving images, descriptions such as ‘sharp' and ‘blurry' seem in some indirect or nonliteral way to convey particular aspects of what it is like to have these experiences. In a relatively cautious use of the word ‘qualia', particular what-it-is-like properties, whatever their nature turns out to be, are qualia. There are bolder uses of ‘qualia' on which the word can apply only to properties of experience that pose challenges to scientific explanation. Some require qualia to be infallibly and completely accessible to introspection, which is puzzling on any plausible scientific explanation of introspection ( §§7-8). Some require qualia to be inaccessible without introspection - for instance by purely behavioural or neurophysiological tests that one may perform on other people, without relying on an introspective understanding of one's own experience; this seems to preclude explanation of qualia as physical properties discoverable in multiple objective ways ( §3). Perhaps the most controversial philosophical idea about qualia, however, is that they are ‘intrinsic' properties of experience. Metaphysicians dispute the correct account of intrinsicality, but the following may serve to convey the intuitive idea, as it applies to experience: for an experience to have a property intrinsically, the experience must have the property solely in virtue of the spatiotemporal parts of what realizes the experience. (This is meant to exclude everything that even in part exists when or where the experience does not, for example, stimuli that cause the experience, and behaviour and other mental states that the experience causes.) This seems to preclude explaining qualia in ‘functionalist' terms by appeal to the causal role of experiences, or in ‘intentionalist' terms by appeal to the representational content of experiences ( Functionalism). Defenders of the intrinsicality of qualia often argue for the possibility of ‘inverted qualia', cases in which two experiences differ in qualia even though they have identical causal or representational relations to their mental and non-mental surroundings ( Block 1990). Qualia in such bold senses have been rejected most forcefully by Dennett (§3). He describes several examples in which changes in whether we like or dislike certain tastes seem to change the tastes themselves, concluding that when someone ‘thinks of "that taste" he thinks equivocally or vaguely' and ‘need not try - or be able - to settle whether he is including any or all of his reactions' (1988: 61-3). Nevertheless he accepts that, through the changes in likes and dislikes, ‘the taste is (sort of) the same', and defenders of intrinsicality may hope to explain such taste similarities by appeal to reaction-independent components of experiences ( Lormand 1994 for further defence of bold qualia). An argument against the existence of intrinsic qualia can be built upon what G.E. Moore calls the ‘diaphanousness' of perceptual experience: The moment we try to fix our attention upon consciousness and to see what, distinctively, it is, it seems to vanish: it seems as if we had before us a mere emptiness. When we try to introspect the sensation of blue, all we can see is the blue: the other element is as if it were diaphanous. (1903: 450) Gilbert Harman argues as follows: When you see a tree, you do not experience any features as intrinsic features of your experience. Look at a tree and try to turn your attention to intrinsic features of your visual experience. I predict that you will find that the only features there to turn your attention to will be features of the presented tree, including relational features of the tree ‘from here'. (1990: 39) Defenders of intrinsicality may claim not to satisfy Harman's prediction. This response gains plausibility in cases of degraded perception (for example, blurred or double vision), and it is not clear how Harman's argument is supposed to generalize from perceptual experiences to bodily-sensational, imaginative or thought experiences ( bodily sensations; Imagery). (For discussion of imagery by a philosopher in sympathy with Harman, see Tye (1995).) The prediction may hold for non-degraded perceptual experiences and perhaps ‘upgraded' imaginings such as dreams, and in these cases perhaps it shows that no experienced features seem intrinsic to experience. One may hold that some experienced features are intrinsic to experience, but only by incurring a burden of explaining why these features seem to belong to trees and other non-mental objects. In fact, this burden remains even if qualia are taken to be relational features of perceptual experience, since the relevant experienced features are experienced as if they belong objectively to trees, and do not seem in experience to depend on the participation of the perceiver. Just as the eliminativist about phenomenal objects of experiences would do well to explain the illusory experience of their presence, so the non-eliminativist about phenomenal properties of experience - whether intrinsic or relational - would do well to explain the illusory experience of their absence ( Qualia). 6 Introspection and the phenomenal Here the discussion begins to shift from phenomenality to introspection. To clarify the apparent difference between phenomenal and introspective consciousness, consider whether a state can be conscious in one but not the other sense. Can there be nothing it is like to have a state, even when one is introspectively aware of it? Can there be something it is like to have a state, even when one is wholly unaware of it? The facts are murky and controversial, but it is important to be clear about the possibilities. The introduction lists four kinds of states that are most clearly phenomenal: perceptual experiences, bodily-sensational experiences, imaginative experiences and streams of thought. There are mental states not explicitly on this list, notably ‘propositional attitudes' such as the belief that snow is white ( Propositional attitudes). Usually one's belief that snow is white is latent and unintrospected, though one can raise it to introspective consciousness easily. Normally there seems to be something it is like to have such an introspectively conscious belief ( Belief). However, there is another possibility to explore. What having the belief ‘is like' may be completely accounted for by what it is like to have experiences accompanying the belief, such as auditory imaginings of asserting the words ‘Snow is white' (or ‘I believe snow is white', or ‘Mon Dieu! La neige! Blanche!'), or visual imaginings of some fictitious white expanse of snow, together with what William James (1890: 287-8) describes as feelings or imaginings of moving eyeballs, eyelids, brow, breath, jaw-muscles and so on as one thinks. Pending evidence of further aspects of what it is like to have the belief, this illustrates how there can be something it is like when one has an introspectively conscious state, although the state itself has no phenomenal character (Lormand 1996). Introspective consciousness - at least of the sorts available to beliefs - is unlikely simply to be phenomenal consciousness, and is unlikely to be sufficient for it. Might introspection nevertheless be necessary for phenomenality? There is a tension between a ‘yes' answer and the view that many species of animals can have experiences - that there is something it is like for cats and dogs to feel pain or to see bright lights, for instance. It is implausible that these beings have Cartesian reflective knowledge that they feel pain and see. This would require having concepts of feeling pain and of seeing, and perhaps a self-concept, and all this would seem to involve capacities beyond the reach of most nonhuman animals - for example, the ability to conceive of others as feeling pain and seeing, and the ability to remember or envisage oneself feeling pain and seeing ( Animal language and thought). Notoriously, Descartes himself accepts that nonhuman animals are ‘automata' without mental states of any sort. Defenders of a reflective-knowledge requirement may either mimic this strategy, denying that animals have conscious experiences (Carruthers 1992), or else attempt to minimize the conceptual sophistication needed for the reflective knowledge (Rosenthal 1990). This tension is more commonly taken to be a serious strike against a reflective-knowledge requirement on phenomenality, especially given that a similar tension arises in the case of human infants. Thomas Reid objects against Locke that ‘reflection ought to be distinguished from consciousness', since: From infancy, till we come to the years of understanding, we are employed solely about external objects. And, although the mind is conscious of its operations, it does not attend to them; its attention is turned solely to the external objects, about which those operations are employed. ([1785] 1969: 57) Even for beings with the requisite conceptual capacities, it seems implausible that reflective knowledge must accompany each of their experiences. At any given moment one can attend only to a small proportion of the sensory stimuli one encounters. It is also difficult to attend simultaneously to the outside world and to one's experience of it, as Auguste Comte argues (1842: 21): ‘The thinking individual cannot cut himself in two - one of the parts reasoning, while the other is looking on' ( Introspection, psychology of). Nevertheless, plausibly, there is something many inattentive perceptions of unattended stimuli are like; experience would be quite impoverished were it not for the contributions of background noises and odours, pressures on one's feet or seat, moisture under one's tongue, peripheral vision and so on. It is possible to maintain that one continually forms reflective beliefs about these experiences, but this fits poorly with the difficulty of remembering these experiences (after they change, for example). An introspective requirement on phenomenality can blunt much of the force of these objections by distinguishing inner perception from the formation of reflective beliefs, and by distinguishing inattentive introspection from attentive introspection. Just as one might sense a daffodil without having a concept of daffodils, or a tendency to remember the daffodil, so perhaps one can inwardly sense an experience without having a concept of experiences, or a tendency to remember the experience. Animals and babies might sense even if they cannot form beliefs; likewise, perhaps they can inwardly sense even if they cannot form reflective beliefs ( Belief). Also, according to Locke, just as there can be passive sensation, so reflection need not be done intentionally or with attention (1689: II.i.7). Along these lines, Brentano distinguishes between inner perception, which may be automatic and inattentive, and inner observation, which is actively guided by purposeful attention (1874: 29). It is true that a creature's most pressing cognitive needs require mental resources to be directed at the external world, but if inner perception is normally inattentive, it need not draw resources away from attentive outer perception ( Bodily sensations). It is an open question whether there can be phenomenal experiences without any kind of introspective awareness of them, even of a primitive sort. 7 Completeness of introspection Perhaps more thoroughly than Descartes ( §1), Locke identifies the mental with the introspectively conscious, claiming that it is unintelligible ‘that any thing thinks without being conscious of it, or perceiving, that it does so' because ‘thinking consists in being conscious that one thinks' (1689: II.i.19). This completeness claim has been rejected by most subsequent philosophers, with the prominent exception of some in the broadly phenomenological tradition, following Franz Brentano and Edmund Husserl ( §10). The main evidence for introspectively unconscious mental processes is that they would fill certain theoretical gaps in the scientific explanation of behaviour and introspectible mental activity. This inferential strategy is most prominent in psychoanalytic attempts to explain otherwise bizarre dreams, associations among concepts, apparent slips of the tongue, emotional disorders, neurotic physiological reactions and so on ( Freud, S.; Psychoanalysis, post-Freudian; Unconscious mental states). Although the scientific status of such clinically-based explanations is controversial ( Psychoanalysis, methodological issues in), alternative explanations are elusive; witness Sartre's difficulties in trying to explain self-deception and ‘bad faith' without appeal to unconscious mentation (1943). Furthermore, many replicable psychological experiments lead to parallel conclusions about introspectively unconscious mentation in more mundane settings. In one family of experiments (Lackner and Garrett 1972), subjects are presented with an ambiguous sentence in one ear, and disambiguating words in the other ear, but so quietly as not to be noticed consciously by the subjects - typically the stimulus is reported as a meaningless noise. Nevertheless, the subjects' interpretations of the ambiguous sentence are predictable from the meanings of the disambiguating words. This is evidence that subjects not only identify but understand the words, without introspective consciousness of doing so. Similarly, there is evidence of vision without introspective consciousness of vision in cases of subliminal visual perception (Dixon 1987) and ‘blindsight' (Weiskrantz 1988). In these cases subjects act on the basis of information about the visual features of objects, despite denying - sincerely - that they have relevant visual experiences. Blindsight subjects have damage to certain neural pathways connecting portions of the retina to the visual cortex, yet in some sense they have perceptual states sensitive to these stimuli. For example, some ability to discriminate an ‘X' from an ‘O' is intact. This is evidenced by the preponderance of correct answers they can give to questions about the stimuli. When asked to reach for objects in blindsight regions, also, some subjects reflexively pre-orient their hand and fingers in ways suited to the specific shapes of the objects. What blindsight patients lack most clearly is any ability to introspect their perceptual states and abilities: they deny that they are perceiving; they respond to the stimuli only when coaxed to do so; and even then they take themselves merely to be guessing. Nevertheless, their guesses tend to be correct and their behaviour appropriate to the stimuli. It is not only in unusual cases that there seem to be introspectively unconscious perceptual states. On virtually all detailed theories of normal vision, for example, cells in each retina register the amount of incoming light at various points, and cause further states representing sudden discontinuities of incoming brightness, which cause further representational states and, eventually, introspectively conscious visual experiences ( Vision). These early layers of visual processing seem well beyond the reach of introspection. Although these processes (unlike, say, blood flow in the brain) have many mentation-like features - they are assessable as correct or incorrect in relation to external stimuli; they may increase gradually in stability as evidence for them mounts; they may play a direct role in modulating intentional visuomotor action, and so on - they are at best somewhere in the vague boundary between the mental and the non-mental. To the extent that introspectively unconscious perceptual states are phenomenal, they present a new threat to the claim that introspection is necessary for phenomenality ( §6). Disagreement arises about whether cases of subliminal perception or blindsight involve phenomenal consciousness - perhaps blindseeing is like something, despite the subject's sincere denials; at any rate the cases are not clear enough to weigh decisively against the necessity claim. There is more dispute about whether non-introspectible information-bearing states in early visual processing are phenomenally conscious. On the view that they are, it would be difficult to explain why phenomenal visual experiences are not continually like double images, given that one has separate left-eye-caused and right-eye-caused early visual states. On behalf of the view, one possibility is that there is something it is like for one's early visual systems to have certain states, although there is nothing it is like for one to have them. Although this is a possibility, it seems no more likely than the possibility that there is something it is like for one's neurons when they fire. 8 Reliability of introspection Even if introspective consciousness is limited, it may be epistemologically interesting as an especially reliable means of access within its domain ( Introspection, epistemology of). Many philosophers have thought that introspective access to mental facts is more reliable than access to other empirical facts. Augustine writes in On the Trinity that ‘nothing can be more present to the mind than the mind itself' (X.3.5), and asks rhetorically, ‘what is so intimately known as the mind, which perceives that it itself exists and is that by which all other things are perceived?' (VIII.6.9). Descartes devotes his Second Meditation to an argument that the mind is ‘better known' than the body, and Locke also claims that our knowledge of ‘Things without us' is ‘not altogether so certain, as our intuitive Knowledge' (1689: IV.xi.3). As with completeness, most subsequent philosophers reject the infallibility of introspection, although many would agree that it is relatively reliable. The claim of introspective infallibility is extremely bold. In other empirical domains, at best certain mechanisms keep one's beliefs in rough accord with the facts (for example, mechanisms of perception, reason and memory, and the persistence of facts when one is not continually checking them). But mechanisms fail; a mechanism of this complexity that could never possibly fail would be a miracle ‘at least as mysterious as papal infallibility', according to Dennett (1988: 55). The same reason to expect fallibility holds for introspection: if there is the slightest mechanism correlating one's thoughts with one's thoughts about them, it should be breakable, and if there is no mechanism, a perfect correlation between the two would seem to be sheer luck. Furthermore, scientific investigations of introspection have revealed widespread ‘confabulation' in self-access. In identifying one's beliefs and motivations, one systematically but sincerely reports attitudes one thinks rational or statistically normal in the circumstances, even if one does not have them ( Nisbett and Wilson 1977; Introspection, psychology of). For instance, in the ‘bystander effect', increasing the number of joint witnesses to a person's need decreases the likelihood that any of them will assist. But bystanders rarely report this as a factor in their decision whether to help, often claiming instead to have reached a decision based solely on their own likelihood of success. According to Nisbett and Wilson, much allegedly ‘introspective' access to attitudes consists of self-directed, fallible guesses, based at best on common-sense abilities to rationalize behaviour. Also, since these abilities are at work in one's access to others' mental states, this self-directed guesswork provides some reason to suppose, with Ryle (1949), that introspective consciousness is not interestingly more reliable than access to other minds. In the face of this evidence, the Cartesian may attempt to identify a restricted domain in which a kind of introspection is comparatively reliable (Ericsson and Simon 1993) or even infallible (Lormand 1994). The model of rationalizing or statistical guesswork does not extend easily to introspection of phenomenally conscious experiences. For example, untutored subjects offer consistent and apparently reliable reports of ‘feelings' of stinging (rather than throbbing) pain when a limb has restricted blood flow. They seem not to infer these feelings in the way one might form beliefs about another's pain feelings, since no common-sense principles of rationality dictate that one should feel stinging rather than throbbing, and since the subject need know no relevant statistical information about how people feel in these circumstances. Against any attempt to find a restricted domain safe for infallibility, Dennett argues that one can easily be wrong about the ‘changes and constancies' in one's experience over even brief intervals of time (1988: 59). This weighs against infallible memory access to what it was like to have past experiences, though not against infallible or especially reliable access to current experiences. 9 Introspection as inner perception How should introspective consciousness be explained? While Lockean inner perception ( §2) has some contemporary defenders, most notably David Armstrong (1980), this view has fallen on hard times in philosophy of mind. How is inner perception supposed to be distinctively analogous to outer perception? Of course, inner perceptions are not generated by literal inner eyes, ears and their attendant experience-forming processes. Armstrong explains inner perception as being, like outer perception, ‘selective' (incomplete), ‘fallible' and ‘causal'. This illuminates little, since probably all cognitive processes have these features, even one's most theoretical (versus perceptual) scientific beliefs, for example, those about quantum mechanics or cosmology. Another initially tempting idea is the Hindu one ( §1) that inner perception is a causal but non-inferential source of evidence about mental states (or, more cautiously, that it is as low as outer perception on flexible, all-things-considered inference). Might a mental state be introspectively conscious only if its bearer inwardly perceives the state, in this sense? One strong objection is that introspective access often involves self-directed theoretical inferences, often confabulatory ones. It is therefore best to restrict inner-perception views to current phenomenal experience (in accordance with the suggestions at the end of §8). An influential objection is that inner perception requires phenomenal ‘sense data' interposed between physical objects and one's perceptions of them ( Sense-data; Perception). Accepting inner perception may seem to involve accepting that one at best perceives outer objects indirectly through perceptions of phenomenal mental entities. But such a mediation theory would have difficulty explaining why inwardly perceiving sense-data did not in turn require perceiving further entities (‘sense-data data') and so on, infinitely. Such arguments against sense-data have been mounted against inner perception (as in Shoemaker 1994), but with unclear effect. Inner perceptions need not be interposed between objects and one's perceptions of them - the causal chain in perceiving a table need not proceed from the table to an inner perception and then to a perception of the table. Rather, on a more natural view, the causal chain goes directly from the table to a perception of the table, and then (in cases in which the table perception is introspectively conscious) to an inner perception of the perception of the table. Dennett argues that inner perception of a ‘Cartesian theatre' of consciousness would be too sharp to explain the vague conscious/unconscious distinction, and that inner perception is wasteful - ‘once a discrimination has been made once [in outer perception], it does not have to be made again' (1991: 127). Yet it can be vague whether something is inwardly (or outwardly) perceived, and inner perception of an outer perception need not re-represent features the outer perception is of, but instead may newly represent features of the outer perception ( Lormand 1994, for further defence of inner theatres). Perhaps the most influential objection to inner-perceptual introspection is based on Moore's ‘diaphanousness' claim ( §5). The objection is that, since each outer-perceptual modality (ing, hearing and so on) makes its own distinctive contribution to what experience is like, an additional modality of inner perception should be expected to make its own contribution, to change what it is like. But what it is like to introspect a perceptual experience seems simply borrowed from what it is like to have the experience itself (McGinn 1982: 50-1). When one tries to attend to features of normal experiences, one normally ‘sees through' the experiences to outer objects. So a fundamental disanalogy between outer perception and alleged inner ‘perception' is that the former, but not the latter, has its own phenomenology or perceptual quality. This is evidence against inner perception of current phenomenal experiences. On the other hand, if inner perception is necessary for phenomenality ( §6), then instead of borrowing phenomenal qualities from an outer perception, as the diaphanousness objection alleges, inner perception helps generate these qualities together with the (otherwise phenomenally unconscious) outer perception. This may explain why inner perception does not add further qualia to an outer-perceptual experience; inner perception may already make its phenomenal contribution in the generation of an outer experience with qualia ( Qualia). 10 Alternatives to inner perception Two rivals to inner-perception accounts treat introspective access as epistemically less intimate than inner perception. First, James maintains that introspection is always retrospective (1890: 187-), largely in reaction to Comte's denial that the mind can simultaneously split between ordinary thinking and awareness of that thinking ( §6). James is unhappy with Brentano's response to Comte - that inattentive perception can be split between outer and inner domains - because James seeks to defend the reliance on careful, attentive introspective reports in experimental psychology ( James, W. §2). Second, some maintain that introspection is always laden with theoretical (versus perceptual) inferences. The experimental evidence for confabulation and expectation-driven inference ( §8; compare with Lyons 1986) suggests that introspection is often theory-laden and retrospective, but does not suggest that all cases of introspective consciousness are, including the seemingly non-inferential consciousness of phenomenal experiences that seem to persist while being accessed. One theory of consciousness that combines naturally with theory-ladenness is Rosenthal's ‘higher-order thought' theory (1990). (A thought or belief is ‘higher-order' in virtue of being about mental entities rather than non-mental entities.) According to Rosenthal's view, a mental state is conscious just in case one forms, in a suitably direct way, a thought that one has the state. The state may generate its higher-order thought through inference so long as these inferences are not themselves conscious. This condition is intended to rule out cases in which one comes to think about a state through very indirect inference - say, solely through believing the testimony of a psychologist. On this view, even if introspective access to phenomenally conscious experiences is somehow inferential, it would seem non-inferential simply because one lacks higher-order thoughts about the inferences. At the other extreme from defenders of theory-ladenness and retrospection, many phenomenologists reject inner perception as not being intimate enough to explain introspective access. On one suggestion, some introspectively conscious mental states ‘reflexively' represent themselves (in addition to representing other things). This conclusion is often embraced to avoid an infinite regress threatening the assumption that introspection is complete ( §6): an experience represents itself rather than being represented by a separate introspective state which (assuming completeness) must in turn be represented by a separate introspection of the introspection, and so on. Brentano argues that ‘The presentation which accompanies a mental act and refers to it is part of the object on which it is directed' (1874: 128). Husserl also suggests that ‘In the case of a perception directed to something immanent [that is, roughly, mental],…perception and perceived form essentially an unmediated unity, that of a single concrete cogitatio' (1913: 112). And Sartre insists that ‘the first consciousness of consciousness' - what he calls ‘pre-reflective consciousness' - ‘is one with the consciousness of which it is [a] consciousness' (1943: 13-14). Given the prevalence of inferential, confabulatory access to one's mental states, reflexivity theories, like inner-perceptual ones, are best restricted to current phenomenally conscious experiences rather than to other mental states. Again, there is a possibility that one's only access even to these experiences is somehow much more confabulatory or inferentially sensitive to expectations than ordinary perception is, but pending evidence for this possibility the restriction to phenomenal experiences is reflexivity's best hope. Since one often suffers ordinary perceptual illusions, the more analogous introspection is to perception, the more likely it would be that one would suffer naïve introspective illusions about what one's conscious experiences are like. But it rarely if ever happens that one mistakes, say, a dull pain for a sharp pain, in the way that one mistakes a