CONSCIOUSNESS

The term consciousness refers to several distinct, but related phenomena that figure in the mental functioning of people and other creatures.

Kinds of Consciousness

One of these phenomena is closely tied to simply being awake. An individual is conscious if it is awake and responsive to sensory stimulation; a person or other creature that is asleep, in a coma, or knocked out is not conscious.

There are also other phenomena we refer to as consciousness. One is conscious of something if one senses or perceives the thing or has some suitable thought about it; being conscious of something is being aware of that thing. Because we use a grammatical object to specify what somebody is conscious of, it is convenient to call this phenomenon transitive consciousness, as against an individual's being awake and responsive to sensory input, which we can call creature consciousness (Rosenthal 1990).

We sometimes describe the states one is aware of as constituting one's current mental life as a stream of consciousness. But there are, in addition, thoughts, desires, feelings, and perceptions that occur outside that stream of consciousness, of which one is wholly unaware. Even though one is unaware of these states, they are nonetheless part of one's mental functioning. We call the states that occur in somebody's stream of consciousness conscious, in contrast with those of which that individual is wholly unaware. This is a third use of the term conscious. Because consciousness of this sort is a property of mental states, such as thoughts, desires, feelings, and perceptions, we can call it state consciousness.

Sometimes we focus deliberately and attentively on some feeling or perception we have; such focused awareness of our mental states is called reflective, or introspective consciousness. And we call the explicit consciousness of the self to which these states belong self-consciousness.

There is disagreement about what connections hold among these several kinds of consciousness. Some theorists hold that an individual cannot be creature conscious—that is, awake and responsive to sensory stimulation—unless at least some of its mental states are conscious. Doubtless that is true for ordinary humans; people are never conscious without being in some conscious states. But, if perceptions and feelings can occur without being conscious, there is in principle no reason why some creatures might be awake and responsive to sensory stimulation even though none of their feelings, perceptions, or other mental states are conscious states.

Not all theorists, however, accept that feelings, perceptions, thoughts, and desires can occur without being conscious. Even Sigmund Freud (1961), who championed the idea of unconscious desires and thoughts, drew the line at qualitative states, such as sensations and feelings. All feelings, he held, are conscious, though we can loosely characterize feelings as unconscious when one is unclear or mistaken about what they are about.

Others, such as Thomas Nagel (1974) and John R. Searle (1990, 1992), accept that nonconscious states occur that function in ways similar to conscious feelings, perceptions, and thoughts, but deny that those nonconscious states are full-fledged feelings, perceptions, or thoughts.

It is also a matter of some controversy whether mental states are conscious in virtue of one's being conscious of those states. Earlier writers, such as René Descartes (1984–1991) and John Locke (1975), always described the states we now call conscious as states that one is conscious of. But, because they also held that we are conscious of all our mental states, they saw no need to use the term conscious to mark a distinction between those mental states we are conscious of and those we aren't. When, in the late nineteenth century, it became widely accepted that individuals are in some mental states of which they are wholly unaware, the term conscious came to mark the contrast between those mental states one is conscious of and those one is not.

Though not all theorists agree that a mental state's being conscious involves one's being conscious of that state, that has long been the dominant view.

Qualitative Consciousness

Mental states fall into three broad groups. Some, such as beliefs, thoughts, desires, hopes, and expectations, have intentional content that can be described by a sentential clause. Thinking is always thinking that something is the case; the clause beginning with that specifies what it is that one thinks. Similarly with one's desires, hopes, and expectations. The intentional content, described by a that clause, specifies what it is that one desires, hopes, or expects.

Pains and other sensations, by contrast, have no intentional content, but instead exhibit some qualitative character, such as the quality of painfulness or the color qualities of visual sensations. A third group of states includes emotions and perceptions, which exhibit both qualitative character and intentional content.

Many theorists hold that the consciousness of qualitative states is something different from the consciousness of other mental states, and that it demands special treatment. Giving an informative theoretical account of qualitative consciousness, on their view, faces special difficulties.

Thus Ned Block (1995) has urged that qualitative states exhibit a special kind of consciousness, which he calls phenomenal consciousness, or phenomenality. A state has phenomenal consciousness, according to Block, if there is something it is like to be in that state, which happens only when the state has some qualitative character. There is nothing it is like simply to think or believe something, even when one's thought or belief is conscious. Phenomenal consciousness occurs only with states that have qualitative character.

Block (1995) distinguishes a state's having phenomenal consciousness from its having what he calls access consciousness. A state is access conscious if its content is poised to figure in reasoning and in the rational control of action and speech. Some qualitative states, which exhibit phenomenal consciousness, also exhibit access consciousness; intuitively, they are the qualitative states one is conscious of. By contrast, when a state is phenomenally conscious but not access conscious, one is wholly unaware of the state. And there is often compelling empirical or theoretical reason to think that qualitative states of which one is unaware do occur (see the next section in this entry).

Block's notion of access consciousness echoes Daniel C. Dennett's (1993) idea that a state's being conscious consists in its having "cerebral celebrity," that is, if it has a widespread effect on memory and on the control of behavior. It also accords with the cognitive theory of consciousness advanced by the psychologist Bernard J. Baars (1988), on which a state is conscious if it occurs in a global workspace that maximizes its connections with other states and behavior.

Problems about Qualitative Consciousness

A state's being access conscious consists in its having suitable connections with other states and with behavior. So the notion of access consciousness invites a functionalist account (Lewis 1972, Putnam 1975), on which a state's mental properties are a matter of such connections. Many theorists, however, deny that any such an account can work for qualitative consciousness. They insist that, because conscious qualitative character is an intrinsic property of sensations, it cannot be understood in terms of connections that sensations have with other things.

explaining conscious qualities

The new physics pioneered in the seventeenth century by Galileo Galilei, Descartes, and Isaac Newton holds that we can explain the nature and behavior of physical objects only insofar as we can describe them in mathematical terms. Since commonsense physical qualities, such as color and sound, seem to resist mathematical description, some have followed Locke in construing such properties as powers to cause the corresponding mental qualities. But conscious mental qualities also resist mathematical description, and it may seem that no parallel move is possible for them. Many conclude that conscious mental qualities lie outside the reach of physical explanation, and possibly, therefore, any informative explanation. Thus, Locke argued that sensations either are nonphysical states or, if they are states of material bodies, they must be "superadded" to those bodies by God.

In a somewhat similar spirit, Joseph Levine (2000) has argued that there is an "explanatory gap" that blocks any intelligible explanation of conscious qualitative states in terms of physical processes. Similarly, Nagel (1974) has argued that none of the available naturalist theories of mind can explain what it's like for one to be in a mental state. And David Chalmers (1996) has described as the "hard problem" of consciousness the question why relevant brain processes are accompanied by qualitative consciousness at all, and why particular brain events are accompanied by specific types of mental quality.

Levine has urged that, though we cannot explain qualitative consciousness in physical terms, qualitative consciousness might nonetheless be physical in nature. Others conclude instead that qualitative consciousness cannot have a physical nature, arguing that any such physical nature would make possible a physical explanation of qualitative consciousness. And Colin McGinn (1991) has argued that, though consciousness is physical in nature, we lack the cognitive capacity to understand how that is possible.

It is unclear, however, that the considerations used to support these views are compelling. We rely on well-developed theories to draw systematic connections among things in nature. Even the most ordinary connections among natural processes seem surprising and unintelligible without any commonsense theory to provide context, and come to seem rational only when subsumed by some suitable theory. So it may be that the ties between conscious mental qualities and brain processes now seem unintelligible only because we still have no well-developed theory that links them. But by itself, that current lack gives us no reason to doubt that we will some day have such a theory. And coming to have one would likely overcome any prior intuitive concerns about explaining qualitative consciousness, just as physics and chemistry have made intuitively acceptable various explanations of our commonsense world that would previously have seemed outlandish.

Introspection may also seem to support intuitive doubts about whether rational explanation of conscious qualitative character is possible, since introspection provides no clue about how such an explanation might proceed. But we have no reason to think that introspection would help here; introspection can at most tell us about the qualities themselves, not how they connect with other things.

the knowledge argument

Frank Jackson (1982, 1986) has argued that conscious qualitative states are not physical because, even if one knew everything physical there is to know about our psychological and neural functioning, one would not thereby know what it's like for one to be in particular qualitative states. Jackson imagines a neuroscientist who knows everything physical about visual functioning but has never seen anything except in black, white, and gray. Still, Jackson argues, this neuroscientist, on consciously seeing red for the first time, would learn something new, namely, what it's like for one to see red. Since the neuroscientist already knew everything physical about seeing red, the new knowledge of it what it's like for one to see red cannot be knowledge of something physical.

Jackson (2003) has since repudiated this argument, maintaining now that what it's like for one to see red is purely a matter of intentional content. This view is a version of representationalism, which is discussed later in this entry. Others have responded differently to Jackson's original argument, urging that what one would learn on first consciously seeing red is not factual knowledge, but only a kind of acquaintance (Churchland 1985) or an ability to recognize the quality in question (Lewis 1990; cf. Loar 1997).

qualities and consciousness

Some theorists contend that qualitative states of which we are in no way conscious cannot occur. Indeed, the very term qualia (singular quale ) is often applied to mental qualities with the implication that such qualities cannot occur without being conscious. But there is compelling reason to holdthat mental qualities do occur outside our stream of consciousness.

Individuals sometimes perceive things without being at all aware that they are doing so. In so-called masked priming experiments (Marcel 1983), subjects briefly exposed first to one visual stimulus and then to another may consciously see only the second. Nonetheless, it is plain that subjects do see the first stimulus, since it affects subsequent behavior in ways characteristic of seeing those stimuli. Thus, subjects who report seeing only the second stimulus can nonetheless make strikingly accurate guesses about the first.

There are other such cases. Individuals with lesions in the cortical area primarily responsible for vision may be wholly unaware of seeing a stimulus and yet guess about its visible character, again with great accuracy, exhibiting what Lawrence Weiskrantz (1997) has called blindsight. These individuals see stimuli, but are not in any way conscious of seeing them. And subliminal perceiving, of which one is wholly unaware, sometimes occurs even in everyday situations.

Not only do qualitative states sometimes occur without being conscious; there are circumstances in which we are conscious of ourselves as being in qualitative states that are different from those we are actually in. John Grimes (1996) reported that subjects will continue to see a highly salient object as unchanged in color or other respects if the relevant changes occur during a saccade, since no visual input reaches the brain during saccades. A subject may thus attentively look at something red but be conscious instead of seeing green. Such a subject would presumably have a sensation of red, despite being conscious of having a sensation of green. Our consciousness of our qualitative states can sometimes be strikingly inaccurate.

According to Block (1995), cases of qualitative states that occur outside our stream of consciousness are phenomenally conscious states that lack access consciousness. Access consciousness makes the difference, he urges, between qualitative states of which we are intuitively aware and those of which we are not. But it's likely that even qualitative states that intuitively occur in one's stream of consciousness sometimes lack access consciousness, on Block's official definition. Visual states near the periphery of our visual field are conscious but are not, without some shift in attention, poised to figure in any general way in reasoning and the rational control of action and speech. Similarly with other perceptual states that lie outside our focus of attention but are nonetheless part of our stream of consciousness. It is likely that access consciousness has more to do with attention than with consciousness.

quality inversion

Qualitative states figure in perceiving. There is a distinctive mental quality that occurs when one sees something red and a different quality when one sees something green; similarly for perceptible properties accessible by modalities other than vision. That raises the question whether particular mental qualities might play different perceptual roles from one individual to another, or even different roles in the same individual at different times. The question is not about the slight variations in the way people see things, which are detectable in standard ways, but about whether particular mental qualities could play different perceptual roles in ways undetectable by others.

Locke held that such inversion of mental qualities is at least conceivable, and many contemporary theorists share that view. This idea very likely reflects a conviction that mental qualities are individuated solely by the way one is conscious of them, that is, by how they appear to consciousness. If any other factors do figure in the individuation of mental qualities, those factors would enable the detection in others of inversion in the perceptual roles of their mental qualities.

But if mental qualities were individuated only by how we are conscious of them, they would differ only in the way they appear to consciousness. And then mental qualities could not occur without being conscious. Indeed, the evidence that mental qualities do occur without being conscious provides ways of determining their occurrence independent of consciousness. So, that evidence also suggests that any conceivable quality inversion would have to be detectable. It is therefore likely that any satisfactory way of individuating mental qualities will rely on their role in perceiving, independent of whether that perceiving occurs consciously (Rosenthal 2005).

Consciousness and Intentionality

As noted earlier, intentional states, such as thoughts, desires, doubts, and expectations, occur both consciously and not consciously.

Freud posited intentional states that are not conscious as the best explanation of various otherwise inexplicable conscious thoughts and desires and various bits of behavior. Thus, a person may do just those things and have just those conscious thoughts and desires that we would expect if the person also had certain other thoughts and desires. And, if the person is unaware of being in those other thoughts and desires, we can best explain the behavior and conscious states by supposing that the person has those thoughts and desires, but they are simply not conscious. Such reasoning again invites a functionalist account of intentional states, on which the intentional properties of a state is a matter of its connections with other states, behavior, and sensory stimulation. But even apart from a functionalist account, it is widely accepted that intentional states with particular contents have characteristic causal connections with other intentional states and with behavior, and that is all Freud's argument requires. Such reasoning is compelling, moreover, independent of the special kinds of case that interested Freud.

Experimental work in social psychology shows that subjects sometimes report having beliefs or desires that would make sense of a situation or conform to social expectations, despite compelling evidence that these subjects do not actually have those beliefs and desires (Nisbett and Wilson 1977). Not only are we sometimes unaware of our thoughts and desires; in such confabulatory cases we are conscious of ourselves as having thoughts and desires that we do not have.

Searle (1990) has argued that intentional states, properly so called, cannot occur without being conscious. As he notes, one's thoughts and desires always represent things in terms of some aspects and not others; Oedipus had a desire to marry a particular woman, but his desire did not represent that woman as his mother. And, as Oedipus's case illustrates, how one's intentional states represent the things they are about makes a difference both to one's mental life and one's behavior.

According to Searle, the way one's intentional states represent things cannot make a difference to one unless those states are conscious. He concludes that genuine thoughts and desires cannot occur without being conscious. But the way one's thoughts and desires represent things can make a difference to one even if those states are not conscious. A thought or desire need not be conscious to affect one's other intentional states and one's behavior, and it will affect those things differently depending on the way it represents things. Genuine intentional states can occur without being conscious.

Theories of Consciousness I

Theories of consciousness often rely on the traditional idea that a state's being conscious involves one's being conscious in some way of that state. States of which one is in no way conscious are not conscious states. When we are conscious of something, moreover, we can tell others about it. So a standard test for whether somebody is in a conscious state is whether that person can report being in the state. If somebody can report having a particular thought, feeling, or perception, that state is conscious; if the person cannot report being in the state, it is not. This rule of thumb underlies typical methodology in experimental psychology no less than everyday practice.

But the commonsense observation that mental states are states of which we are conscious goes only so far. A theory of consciousness must also specify how it is that we are conscious of those states. One important feature of our consciousness of those states was highlighted by Descartes, who insisted that we are immediately conscious of our mental states. When we are conscious of a mental state, it seems that nothing mediates between that state and our awareness of it. A theory of consciousness must explain this sense of immediacy in the way we are aware of our conscious states.

inner sense

We also seem to be immediately conscious of things when we perceive them; nothing seems to mediate between the things we perceive and our perceptions of them. This encourages the hypothesis, advanced by Locke, Immanuel Kant (1998), and others, that mental states are conscious because we sense or perceive them. A thought, feeling, or perception is conscious because one is aware of that state by way of some faculty of inner sense, or some internal monitoring mechanism that involves the higher-order perceiving of that state. This theory has traditionally been the most widely held explanation of consciousness; contemporary advocates include David M. Armstrong (1978) and William G. Lycan (1996).

But there are difficulties with this theory. Sensations and perceptions always exhibit some qualitative character; sensing a red object, for example, involves a sensation's having a mental quality of red, as against a mental quality of blue, green, and so forth. Our consciousness of our mental states, however, does not involve any qualitative character. This is obvious when the state we are are conscious of is a thought or desire, which itself has no qualitative character; plainly, no mental quality figures in the way we are conscious of those intentional states.

Qualitative character does figure when we are conscious of sensations and perceptions. But these mental qualities are just the qualities we are conscious of our sensations and perceptions as having. As Aristotle (1993) noted, there are no higher-order qualities in virtue of which we are conscious of our qualitative mental states, in the way the mental quality of red enables us to see red objects. Our higher-order awareness of our conscious states may resemble perceiving in other ways, but qualitative character is so central to perceiving that no form of awareness that fails to involve mental qualities can count as perceiving.

Inner-sense theorists often urge that the higher-order sensing or perceiving they posit serves the function of monitoring our mental states, much as perceiving monitors external objects and bodily conditions. But perceiving is not the only way that the mind might monitor itself. And cases of confabulatory awareness, which Richard E. Nisbett and Timothy DeCamp Wilson have demonstrated, do not in any case fit neatly with a model based on monitoring.

intrinsic theories

But we need not appeal to inner sense to capture the apparent immediacy of our consciousness of many mental states. If our awareness of our conscious states were internal to those states themselves, nothing could mediate between a state and one's awareness of it; such consciousness would be intrinsic to each conscious state. This theory, advanced by Franz Brentano (1973) and possibly Aristotle, also has a number of contemporary advocates.

But the intrinsic theory also faces difficulties. There are thoughts and desires that we sometimes have consciously and other times not. A sensation that results from a particular stimulus may be conscious if that stimulus occurs alone, but not conscious if the very same stimulus is followed in a suitable way by a second, masking stimulus (Marcel 1983). It is unclear how we can explain such variation if consciousness is literally built into our mental states.

The problem is particularly pressing when one particular state passes between being conscious and not being conscious. Some perceptual or bodily sensations that are not very intense may be conscious or not depending on where one focuses one's attention. But, since shifts in attention are extrinsic to particular sensations, such shifts should leave consciousness unaffected if consciousness is indeed an intrinsic aspect of mental states.

Brentano held that consciously hearing something makes us conscious of two things: the sound one hears and the hearing itself. And he maintained that we are conscious of the hearing in the way that having a thought about something makes us conscious of that thing, even when we don't perceive it. The intentional content of hearing something, according to Brentano, makes us conscious both of the thing heard and the hearing itself.

Perhaps hearing can have two intentional objects in this way. But there are other cases for which Brentano's model does not work. Doubting something does not make one conscious of the thing one's doubt is about. Consider, then, a case of doubting that it is raining. Even if one's doubt is about both the rain and the state of doubting itself, that will not make one conscious of the doubting. A mental affirmation that one has that doubt would make one conscious of the doubting. But that mental affirmation could not be intrinsic to the doubting, since no mental state involves more than one mental attitude. Similar considerations apply to wondering about something, and many other mental attitudes.

Inner sense and Brentano's intrinsic theory both sought to explain the way our awareness of our conscious states is immediate. But all we really need to explain is why such awareness appears to be immediate, since we do not know that it actually is. Indeed, perceiving is also subjectively unmediated, but we know that there is much that actually mediates between our perceptions and the things we perceive. So the same may well be so with the way we are aware of our conscious states. Despite the subjective impression of immediacy, there may well be mediation we are not subjectively aware of. All we need to explain is the subjective sense of immediacy, and neither the analogy with perceiving nor the intrinsic theory is required for that.

higher-order thoughts

On Brentano's intrinsic theory, every conscious state makes us conscious of itself, in much the way that having a thought about something makes one conscious of that thing. This theory cannot work, at least for cases like doubting and wondering. Inner sense, by contrast, faces the difficulty that, because the awareness of our conscious states does not involve higher-order mental qualities, that awareness cannot be sensing or perceiving. This suggests combining features of the two theories so as to avoid the difficulties of each. Perhaps we are aware of our conscious states by having thoughts about them, as Brentano urged, but those thoughts are distinct from the states we are conscious of, as inner sense maintains about the higher-order perceptions it posits.

This appeal to higher-order thoughts that are distinct from the mental states they make us conscious of avoids the foregoing difficulties that face inner sense and Brentano's theory. The higher-order-thought theory, advanced by David M. Rosenthal (1986, 1990, 2005) and others, also allows for an explanation of the subjective immediacy of our awareness of our conscious states; the theory can require that these higher-order thoughts are independent of any conscious inference. If we are unaware of any inference on which a higher-order thought relies, we will be unaware of any mediation between the states we are aware of and our awareness of them. So, such awareness will be subjectively unmediated. Indeed, we would seldom be aware of these higher-order thoughts, since a third-order thought would be needed for any second-order thought to be conscious. And our typically being unaware of our higher-order thoughts would enhance the subjective sense that our consciousness of our mental states is immediate.

Critics have urged two major difficulties for this theory. One involves the possibility that higher-order thoughts will sometimes misrepresent what mental states we are in. But it is arguable that consciousness does sometimes misrepresent things, as in the confabulatory cases noted earlier. And there are very likely psychological pressures that prevent such misrepresentation from becoming too extreme.

Nonetheless, some have insisted that such misrepresentation cannot occur, in effect relying on the traditional idea, advanced by Descartes, Locke, and others, that the mind is transparent to itself. But there is compellingreason to reject that transparency claim. Confabulatoryconsciousness and other phenomena show that consciousness does occasionally mislead us; moreover, others sometimes know what we are thinking and feeling better than we ourselves do. Consciousness is neither infallible nor exhaustive.

Another challenge to the higher-order-thought theory pertains specifically to conscious qualitative states. How can higher-order thoughts, which themselves lack qualitative character, result in qualitative states' being conscious? How can simply having a thought result in there being something it is like for one to be in a qualitative state?

This challenge echoes the concern that an explanatory gap may make it impossible to understand how conscious mental qualities could arise as a result of particular neural events. Put most generally, the concern is how conscious qualities can result from anything else. But as noted earlier, connections among things in nature seem intelligible only when we have a well-established theory that subsumes those connections. Since higher-order thoughts are seldom conscious, introspection cannot tell us whether they result in conscious qualities. But it may be that the connections higher-order thoughts have with the thoughts we have about the things we perceive result in our being conscious of the mental qualities that figure in such perceiving.

In any case, no alternative theory has a response to this challenge that is at all satisfactory. By itself, simply positing that our awareness of qualitative states is intrinsic to those states does nothing to explain why there is something it is like for one to be in those states. And inner sense faces a regress, since it could help only if the higher-order perceptions themselves had conscious mental qualities, and we would then need to explain what gives rise to those higher-order conscious qualities.

Theories of Consciousness II

The foregoing theories differ about whether our awareness of our conscious states is intrinsic to those states or external to them, and about whether that awareness is due to our perceiving those states or to our having thoughts about them. But there are other issues about which theories differ as well.

dispositional theories

Peter Carruthers (2000) has argued that a state's being conscious does not require the actual occurrence of a higher-order thought, but only a disposition for such a higher-order thought to occur. Carruthers urges that having an actual higher-order thought for each conscious state would result in cognitive overload, unlike one's merely being disposed to have higher-order thoughts.

But there is no reason to think that our cortical resources cannot accommodate actual higher-order thoughts, and dispositions would themselves make substantial cortical demands. Nor is it obvious that dispositions will do. Since being disposed to have a thought about something does not make one conscious of anything, merely being disposed to have a higher-order thought would not make one aware of one's mental states. Carruthers seeks to meet this difficulty by endorsing the view that the intentional content a state has is partly a matter of what other states it is disposed to cause. So, when a state is disposed to cause a higher-order thought, that very state has higher-order content, which makes one conscious of that state. But, since the state itself has the higher-order content, this view faces the same difficulties that tell against Brentano's theory.

representationalism

Some have sought to meet the challenge about conscious mental qualities by denying that there are any. According to representationalism, we are never conscious of any mental qualities, but only the perceptible properties of physical objects, and the states in virtue of which we are conscious of them are purely intentional states. When we see something red, on this view, the only quality we are aware of is the redness of the thing seen; we are not in addition aware of some mental red. Advocates of this view, such as Gilbert Harman (1990), Dennett (1991), Fred Dretske (2000), Armstrong, and Lycan, point out that we never seem to be conscious of two distinct qualities of red, nor to switch from being conscious of the redness of physical objects to being conscious of a mental quality of the seeing itself. Descartes also espoused a form of representationalism, since he regarded all mental phenomena as having only intentional properties, and construed sensations either as purely intentional states or as nonmental bodily states.

But, as Wilfrid Sellars (1963), Sydney Shoemaker (1996), and Rosenthal (2005) have argued, perceptual sensations resemble and differ in ways that reflect the similarities and differences among perceived physical properties. And it is natural to construe the properties in virtue of which those sensations resemble and differ as mental qualities. When we introspectively attend to our qualitative states, moreover, we sometimes become conscious of the relevant qualities as qualities of our experiences. So it may well be that we are, after all, often aware of mental qualities that our qualitative states exhibit.

Some theorists, such as Dretske (1993) and Searle (1992), reject the idea that a mental state's being conscious is a matter of one's being conscious of that state. A state's being conscious, on their view, does not involve some higher-order awareness of that state. Rather, according to Dretske (1993), a state is conscious if, in virtue of one's being in that state, one is conscious of something. This is sometimes called a first-order theory of consciousness, in contrast to theories that posit some higher-order awareness.

This account faces a difficulty, however. Perceptions sometimes occur without being conscious. But it is arguable that even those perceptions make us conscious of things. If perceiving something primes one for some conscious state or some behavior, then one was conscious of the thing one perceived even if it did not seem to one that one perceived it. On Dretske's (1993, 2000) view, however, any state in virtue of which one is conscious of something is conscious. And that has the unwelcome result that even the perceptions we seem subjectively not to have are conscious.

Searle (1992) holds that we can subjectively draw no distinction between a conscious state and one's consciousness of it. He concludes that no higher-order awareness figures in a state's being conscious. But when we focus introspectively on our conscious states, we are often aware both of the state thus scrutinized and of the scrutinizing itself. And even if we could not draw that distinction subjectively, we might still have sound theoretical reasons to insist on it.

dennett's theory

Dennett (1991) has developed an important theory of consciousness, which emphasizes cases in which consciousness misrepresents what mental states we are in. Visual information that is not central to our focus of attention can be highly degraded, but still we seem subjectively to see things in sharp detail throughout our field of vision. Dennett argues that consciousness extrapolates from available visual information to create a full picture of the environment, in effect filling in missing visual information and providing missing details.

In thus distinguishing the way consciousness represents things from our actual visual states, Dennett's (1991) view resembles higher-order theories, on which our higher-order awareness of mental states is distinct from the states themselves, and so can misrepresent them. But Dennett rejects such higher-order views, arguing that there is no distinction between the way things appear and our awareness of how they appear. So, he construes the divergence between consciousness and visual states not in terms of two mental levels—perceiving and our consciousness of perceiving—but rather as the difference between the way things consciously appear and the subpersonal neural events in virtue of which things appear that way.

Dennett shares with the higher-order-thought theory a view of consciousness as a kind of self-interpretation. On both views we interpret ourselves as being in various commonsense psychological states. But, unlike higher-order-thought theorists, Dennett denies that we are actually in any of the commonsense psychological states we interpret ourselves as being in. The only states that figure in psychological functioning are subpersonal neural events of content fixation, complex patterns of which subserve such functioning.

Searle (1992) and Dennett (1991, 1993) both reject any distinction between the mental states one is in and one's awareness of those states, but they do so for different reasons. Searle rejects that distinction because he holds that we cannot draw it subjectively. Dennett, by contrast, maintains that the psychological states we are conscious of ourselves as being in do not actually occur. But it is arguable that suitable patterns of the subpersonal events of content fixation Dennett countenances actually constitute the mental states of commonsense psychology. If so, we can distinguish between those commonsense mental states and our higher-order awareness of them.

Neural Correlates, Function, and the Self

Whether or not conscious qualitative states are physical in nature, few doubt that something specific in brain functioning correlates with qualitative consciousness. This has led to speculation about what that neural correlate of consciousness (NCC) is.

According to Francis Crick and Christoph Koch (1990) the NCC involves the occurrence of synchronized neural oscillation of 35 to 75 hertz in sensory cortex, a synchrony sufficient for a vigorous coalition of neurons firing together. One thing that favors this hypothesis is that such synchronized neural oscillation seems to figure in the way different qualitative properties are bound together in conscious experience. As Anne Treisman (1986) has shown, visual qualities pertaining to color, shape, motion, and orientation occur independently in the early stages of visual processing; so there is a binding problem of explaining how they come together in conscious experience. But these qualities are bound together even when qualitative states are not conscious. So, the neural factors operative in such binding may not be the same as those responsible for qualitative consciousness, and synchronized oscillation may subserve only binding, independent of consciousness.

Mental functioning plays a variety of roles, allowing animals to negotiate their way in the world and to satisfy various needs and desires. What, then, is the specific function of consciousness? The answer depends on which kind of consciousness is at issue. Creature consciousness, which consists in an animal's being awake and responsive to sensory stimulation, plainly functions to enable an animal to satisfy needs and avoid danger. Similarly with transitive consciousness, which consists in a creature's being conscious of various things.

State consciousness, by contrast, consists in a state's occurring in a creature's stream of consciousness, and it is somewhat less clear what function this has. A mental state's function depends on its causal connections with other states and with behavior and sensory stimuli, and the causal properties of thoughts and desires are mainly a matter of their intentional content, whether or not they are conscious. Similarly, the causal properties of qualitative states depend on their mental qualities; visual sensations of red interact causally in ways suitably different from visual sensations of green, again whether or not they are conscious. So it is unclear what additional function might result from these states' being conscious.

One standard answer is that such consciousness functions to enhance reasoning and planning; perhaps decisions and thinking will be more rational if one is conscious of one's thoughts and desires. This idea underlies Block's (1995) claim that a state is access conscious if its content is poised to figure in the rational control of action and speech, Baars's (1988) related suggestion that conscious states occur in a global workspace, and Dennett's (1993) that consciousness is cerebral celebrity.

But many thoughts and desires have global effects on other states and on behavior even when they are not conscious. And even when planning and thinking is not conscious, it often is rational, as when we solve problems by sleeping on them. Indeed, this is just what we should expect if the causal potential of thoughts and desires depends mainly on their intentional content. There is, moreover, compelling evidence that we are conscious of our decisions only after those decisions have been made (Libet 1985), so that being conscious of those decisions cannot affect whether we make them.

According to Dretske (1993), any state in virtue of which one is transitively conscious of something is a conscious state. So on that view, the function of state consciousness coincides with that of transitive consciousness. But if, instead, a state is conscious just in case one is in some suitable way conscious of that state, the function of state consciousness will rather be whatever function is added by one's being thus conscious of the state. And that may be relatively marginal.

When we introspect our mental states by deliberately and attentively focusing on them, we are conscious of the states we introspect as states of ourselves, and we are in that way conscious of ourselves as centers of consciousness. There are several questions about the nature of such self-consciousness. David Hume (1978) urged that, though we are aware of many of our mental states, we are not aware of anything in addition to those states which we might call a self. Hume was operating with a perceptual model of awareness, and it is plain that we do not perceive such a self. But we are sometimes conscious of things not only by perceiving them, but also by having thoughts about them as being present. So having higher-order thoughts to the effect that one is in various mental states will make one conscious of oneself as being in those states, and hence conscious of the self to which those states belong.

As Descartes and Kant stressed, our mental states are conscious in a way that seems to involve an important unity; we are conscious of them as all being states of a single unitary self or center of consciousness. It is not obvious whether some actual unity underlies this appearance of conscious unity (see Marcel 1993, Rosenthal 2005). But even explaining that subjective appearance requires more than simply explaining the consciousness of the relevant mental states.

See also Knowledge Argument; Qualia; Subjectivity.

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David M. Rosenthal (2005)