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)

Consciousness

BASIC DEFINITIONS AND PHILOSOPHICAL ISSUES

HISTORICAL CONCEPTIONS OF CONSCIOUSNESS

THE BIRTH OF EXPERIMENTAL PSYCHOLOGY

BIOLOGICAL, FUNCTIONALISTIC, AND BEHAVIORIST PERSPECTIVES

BIBLIOGRAPHY

Consciousness is a multifaceted phenomenon, and many terms are used to describe its facets. Consciousness, conscious, aware of, experience (noun), and experience (verb)— all these words have different meanings in different contexts and for different people, so generalizations about their meaning will necessarily have limited validity. Considerable discrepancies also exist between the conceptual tools available in different languages for classifying consciousness and related phenomena. So, for example, the French conscience encompasses both “consciousness” and “conscience,” as the latter words are used in English; in German the subtle difference between the meanings of the English words “consciousness” and “awareness” is lost when both these words have to be translated as Bewusstsein.

BASIC DEFINITIONS AND PHILOSOPHICAL ISSUES

Because of these linguistic and conceptual problems, every systematic treatment of consciousness has to start with a set of distinctions and definitions for the purpose at hand. The task of formulating these in a way that makes them useful for people with different mother tongues is far from simple. However, aspects of consciousness and related phenomena can be classified in three basic categories: cognitive consciousness, phenomenal consciousness, and control consciousness. All are the subject of ongoing philosophical debates.

Cognitive Consciousness Also referred to as intentionality, consciousness-of, awareness-of, and transitive consciousness, cognitive consciousness entails a mental relation to an object (not necessarily an existing one), and encompasses phenomena such as thinking of a dragon, becoming aware of the presence of another person, attending to a problem and knowing facts about a certain field. In English, awareness is often a more natural choice than consciousness when the cognitive aspect of consciousness is intended. However, the term “consciousness” is not seldom used in an exclusively cognitive sense—for example, the sociological and political terms class consciousness, gender consciousness, and environmental consciousness. Here consciousness stands for habitual attention to, and knowledge about, the issues in question.

The common denominator of all cognitive consciousness is its directedness toward an object, which may be concrete or abstract. It is an important conceptual fact that a person can properly be said to be cognitively conscious although she is in another sense (phenomenal consciousness, as discussed below) not conscious at all. For example, an environmentally conscious person is still environmentally conscious when sleeping dreamlessly. Similarly, since a person in dreamless sleep knows her mathematics, she is cognitively aware of mathematical facts while sleeping. On the other hand, there are forms of cognitive consciousness that cannot plausibly be ascribed to a dreamlessly sleeping subject, for example, thinking of or presently attending to the facts that she knows.

In this context it should also be mentioned that self-consciousness, which is not seldom given a fundamental role in conceptual schemes for handling matters of consciousness, can plausibly be argued to be a species of cognitive awareness (namely, of oneself). The same holds for reflexive consciousness.

Phenomenal Consciousness A good alternative term is experiential consciousness ; sentient consciousness is often given a similar sense but can also have other connotations. A dreamless sleeper does not have any present experiences (or we may suppose so for the sake of this discussion), and is therefore not conscious in the phenomenal sense. An awake person, on the contrary, usually has sensory and perceptual experiences, feels emotions, and entertains mental imagery; all these belong to her phenomenal consciousness.

Two long-standing controversies in philosophy of mind primarily concern phenomenal consciousness: the mind-body problem and the problem of other minds. What is the relation between the brain and phenomenal consciousness? The philosopher David Chalmers (1996) has called this “the hard problem of consciousness.” The problem of other minds is, can we ever know what another person’s, or another animal’s, experiences are like?

The relations between cognitive awareness and phenomenal consciousness have been the topic of many philosophical debates. One classic debate concerns whether cognition is necessarily rooted in phenomenal consciousness, or whether one could give an explanation of it in purely nonphenomenal (for example, physical) terms. Philosophers in the so-called phenomenological school argue for the first position, whereas most present-day analytical philosophers and cognitive scientists, not only those of a strictly materialist bent, defend the second. Today this discussion is usually presented as an issue about the nature of mental representations. Another important controversy concerns whether phenomenal consciousness depends on cognition: Is a pain or a thought phenomenally conscious only by virtue of one’s being conscious of it, or is phenomenal consciousness rather an intrinsic quality of experiences that can be possessed independently of any reflexive consciousness?

Control Consciousness The meaning of this term, for which there are no common synonyms, partly overlaps with that of what Ned Block (1994) calls access consciousness. In our commonsense understanding of ourselves and other people, as well as in many psychological, psychiatric, and neuroscientific theories, consciousness is given a role for initiating and/or controlling behavior. We talk about doing things with or without conscious intention. Psychologists and neurophysiologists speak about automatic versus consciously controlled behavior. A good example of the latter distinction is given by our ordinary, unconscious control of bodily posture versus conscious attempts not to fall when the automatic control fails for some internal or external reason. In some psychiatric theories, consciousness is even given the role of the superordinate controlling instance of mental life, and all mental disturbances are seen as results of more or less deep-seated disturbances of consciousness.

A philosophically controversial issue here is: How can consciousness have a causal role to play in behavior, if all our behavior stems from processes in the brain (as neuroscience seems to say)? This problem is sometimes taken as a motive for a materialistically reductive analysis of control consciousness. Control consciousness is then explained in terms of physical or biological regulatory processes. However, such an approach also has to explain the fact that many paradigm cases of conscious control (e.g., consciously regaining posture) also have a phenomenal aspect.

HISTORICAL CONCEPTIONS OF CONSCIOUSNESS

The French philosopher and mathematician René Descartes (1596–1650) formulated a philosophical conception of consciousness in which the concept was differentiated from conscience, with which it was previously conflated. Descartes’s dualism is well known, and already in the seventeenth century it posed an embarrassing philosophical issue, the body-mind problem. He regarded body and mind as two separate but interacting substances, body (or matter) being essentially characterized by spatial extension whereas mind is characterized by thinking. For Descartes the presence of conscious states was a mark of human beings, in contrast with animals, which he thought were mechanical automata.

Although a clear emphasis on cognitive consciousness can be discerned in Descartes’s writings, the cognitive, phenomenal, and control dimensions of consciousness cannot really be disentangled in them. In seventeenth-and eighteenth-century British empiricist philosophy, phenomenally conscious processes and our consciousness of them are the main concerns. However, the problems of cognitive consciousness are still of central concern. For the British empiricists, ideas are experiential states that are accessible by means of introspection, but they are also themselves essentially about things.

John Locke (1632–1704) formulated the distinction between an outer sense—our experiential access to material objects—and an inner sense, reflecting on one’s own experiences. His theory of inner sense can be regarded as the first systematic treatise of introspection. By consciousness Locke meant all ideas that passed in a man’s own mind and his self-consciousness about them. Consciousness, not bodily continuity, was regarded as constitutive of personal identity.

The famous principle of association of ideas can be traced to Aristotle, but it was the British empiricists who made it the foundation of a whole new science. Locke’s formulation of the principle became of utmost importance for the development of psychological ideas in later centuries. Our understanding of the world and of ourselves was seen as built up from associations between ideas that are similar or contrasting, or that just happen to be contiguous in our experience. Later schools of association-ist philosophy and psychology (as exhibited in the work of David Hartley, David Hume, James Mill, John Stuart Mill, and Alexander Bain) took it for granted that conscious experience is built up from elements and processes that are discernible to the self-conscious mind. Simple ideas are copies of sensations, and complex ideas are construed from simple ideas according to the laws of association. Mental elements and the principles according to which conscious thoughts—or ideas—are built up and interact can be investigated by introspection.

In the late eighteenth century the German philosopher Immanuel Kant (1724–1804) questioned the program of the British associationist philosopher-psychologists. According to Kant, a science in the strict sense requires both mathematical measurement and experimental procedures. None of this is possible in the case of consciousness, as thoughts do not exist in a spatial continuum and as man cannot divide himself into one observing subject and one observed object.

THE BIRTH OF EXPERIMENTAL PSYCHOLOGY

Trying to overcome the obstacles put up by Kant, German philosophers in the nineteenth century formulated several programs for a science of psychology defined as the study of conscious processes. Based on the psychophysical methods the physicist Gustav Theodor Fechner (1801–1887) had devised in 1860, the German physiologist and philosopher Wilhelm Wundt (1832–1920) institutionalized the new science in Leipzig in 1879 as an experimental laboratory discipline. Wundt and his students defined psychology as the study of immediate experience. They held that it was a proper scientific discipline and that mental processes can be measured provided that one uses controlled experimental methods. Simple introspection was therefore replaced by experimental self-observation, a method that required a painstaking training before the subject could correctly describe the phenomena in his consciousness.

In his Principles of Psychology (1890), the American physician and philosopher William James (1842–1910) described psychology as “the science of mental life.” He tried to give a holistic description of consciousness, stressing consciousness as personal, intentional, selective, shifting, and continuous. James’s discussion of consciousness as “a stream of thought” is very similar to the understanding of consciousness in the theories of Franz Brentano, Carl Stumpf, and Edmund von Husserl. During the late nineteenth and early twentieth centuries, the latter philosophers developed what Husserl (1859–1938) in his 1900–1901work named phenomenology. Phenomenology is a philosophy that emphasizes the intentionality of consciousness and the importance of investigating the detailed intentional structure of consciousness. This should be done by means of a certain method, which, although systematically related to introspection, is not identical to it.

In opposition to the British associationists, the phe-nomenologists stressed the fact that conscious ideas need not be similar to that which they are ideas of. In other words, it is not essential to ideas that they are images of their objects. At the beginning of the twentieth century, the psychologists of the so-called Würzburg school (Narziss Ach, Karl Bühler, Oswald Külpe, and others) took an interest in deeper descriptions of phenomena of consciousness. They found in the experimental subjects’ introspective reports instances of “imageless” conscious phenomena (Bewusstseinslagen ) that in their opinion questioned the traditional associationist psychology.

BIOLOGICAL, FUNCTIONALISTIC, AND BEHAVIORIST PERSPECTIVES

During the late nineteenth century there was widespread interest in the possibility of unconscious mental phenomena. Sigmund Freud (1856–1939) famously formulated a systematic theory, or rather several theories, about the unconscious mind. Such an enterprise requires a theory of consciousness. In a crucial paper written in 1915, Freud distinguishes between a “systematic” and a “descriptive” sense of “consciousness.” The systematic sense is close to what is here called control consciousness. The descriptive sense has essentially to do with knowability, but Freud also speculates that a descriptively conscious mental state is conscious by virtue of its possessing a certain intrinsic quality. In Freud’s later thinking, control consciousness is instead described in terms of the mental systems named ego and super-ego.

Within the American school of functionalism that William James was part of, the aim of studying consciousness was regarded with suspicion. In 1904 James even stated that consciousness did not exist, but he meant that it did not exist as an entity, only as a function. With the behaviorists of the early twentieth century, however, the interest radically shifted from consciousness (now often regarded as a metaphysical concept) to behavior. Humans should be understood through their actions and not their thoughts. The idea of finding the basic laws of mental elements using introspective methods was abandoned. The alternative, nonassociationist approaches, such as phenomenology and Gestalt psychology, were also relegated to a minor role in the psychological community. The behaviorists took diverse philosophical positions: Some took the strong metaphysical position that consciousness does not exist, whereas others only defended a moderate methodological statement to the effect that introspective methods should be abandoned as unscientific in favor of behavioral observation.

Behaviorism was to dominate the behavioral and social sciences from about 1920 to 1960. During this time the Gestalt psychologists, who thought in ways related to both phenomenology and the Würzburg school, kept up a keen interest in the study of perception and other forms of experience and did much valuable research on the structure of consciousness. In many respects the thrust of their work was biological, and they were much opposed to explanations of experience by means of mental laws. In Gestalt theory, immediate experience is a direct result of brain processes and cannot be explained by any association of mental elements.

Consciousness research continued throughout the behaviorist era in the fields of psychiatry and neurology. Karl Jaspers (1883–1969), a psychiatrist and philosopher in the phenomenological tradition, in 1913 created a classification scheme for pathological disturbances of consciousness that is still in use. During the whole of the twentieth century, the understanding of consciousness and its pathology was generally regarded as essential for the psychiatric understanding of patients. Around mid-century, the French psychiatrist Henri Ey (1900–1977)— who was also influenced by phenomenological thinking—formulated a new theory about consciousness, stressing its functional and controlling aspects. In most present-day psychiatric theories, however, consciousness is not given such a central explanatory role.

The Cognitive Revolution In the 1960s an important methodological and theoretical shift in the behavioral and social sciences occurred that is often referred to as the cognitive revolution. It was partly inspired by the possibilities offered by computer modeling of rational processes, and it is no coincidence that the main focus of cognitive psychology is memory and thinking. Consciousness was no longer a forbidden territory. Since the 1960s, cognitive psychologists have also shown a renewed interest in unconscious mental processes such as implicit memory, subliminal perception, and other forms of perception without phenomenal perceptual consciousness (e.g., blindsight).

Although consciousness and several different kinds of introspective procedures have once again been admitted into psychology, the terms introspection and consciousness are not used as frequently by psychologists as they were in the early twentieth century. This may not be of any importance in itself, but it reflects the more serious circumstance that there is a fundamental break of tradition between the old psychology and the new. This break also means that several philosophical and methodological issues, which were common knowledge in the psychological community in the early 1900s, seem to be little known by many behavioral and social scientists of the twenty-first century.

However, there are signs that this situation is changing. Since the 1990s a large amount of interdisciplinary work on consciousness has been accomplished, partly under the auspices of independent organizations such as ASSC (Association for the Scientific Study of Consciousness), but also within the academic programs of many universities around the world. Neuroscientists and philosophers, as well as behavioral and social scientists, participate in this effort. The body-mind problem occupies one focus under the name of a search for “the neural correlate of consciousness.” The role of consciousness in perceptual and motor processes is another much researched and hotly debated topic. Finally, “mentalizing” (ascribing mental states to other people) is a third area of central concern for today’s interdisciplinary study of consciousness.

SEE ALSO Anthropology, Linguistic; Aristotle; Cognition; Epistemology; Freud, Sigmund; Gestalt Psychology; James, William; Kant, Immanuel; Knowledge; Locke, John; Mill, James; Mill, John Stuart; Phenomenology; Philosophy; Psycholinguistics; Psychology; Self-Consciousness, Private vs. Public; Theory of Mind

BIBLIOGRAPHY

Block, Ned. 1994. Consciousness. In A Companion to the Philosophy of Mind, ed. Samual Guttenplan, 210–219. Oxford: Blackwell.

Chalmers, David J. 1996. The Conscious Mind: In Search of a Fundamental Theory. New York: Oxford University Press.

Ey, Henri. 1968. La Conscience. 2nd ed. Paris: Desclée De Brouwer.

Hassin, Ran R., James S. Uleman, and John A. Bargh, eds. 2005. The New Unconscious. Oxford: Oxford University Press.

Hilgard, Ernest R. 1980. Consciousness in Contemporary Psychology. Annual Review of Psychology 31: 1–26.

Hommel, Bernhard. 2007. Consciousness and Control: Not Identical Twins. Journal of Consciousness Studies 14 (1–2): 155–176.

Husserl, Edmund von. 1921. Logische Untersuchungen. Vols. 1 and 2. 2nd ed. Tübingen, Germany: Niemeyer.

James, William. 1890. The Principles of Psychology. Vols. 1 and 2. New York: Dover Publications, 1950.

Jaspers, Karl. 1913. Allgemeine Psychopathologie. Berlin: Springer.

Velman, Max, and Susan Schneider, eds. 2007. The Blackwell Companion to Consciousness. Malden, MA, and Oxford: Blackwell.

Helge Malmgren
Ingemar Nilsson

CONSCIOUSNESS

From the Latin conscientia, a contraction of cum alio scientia (i.e., knowledge along with something else), the reflexive knowledge a knower has of himself and of his act in the process of knowing something other than himself. Consciousness has also come to mean (1) mere awareness of something, (2) awareness of the self here and now undergoing states of consciousness or emotion,(3) awareness of the self here and now existing that has also undergone other states of thought and emotion, and (4) states of thought or emotion previously experienced and retained in memory even though they are not in the field of awareness. This article considers these various meanings under three main headings dealing with epistemological consciousness, psychological consciousness, and consciousness in modern philosophical thought.

EPISTEMOLOGICAL CONSCIOUSNESS

Among scholastics the most frequent epistemological usage of the term is that designating the simultaneous knowledge a knower has of an object and of himself as knower of the object. This usage is here explained in its historical origins, and then as commonly applied by scholastics to sense knowledge, to intellectual knowledge, and to other internal acts.

Historical Origins. There is no clear notion of consciousness among the early Greek philosophers, who were concerned more with the objective world and its processes of being and becoming than with their own activities of knowing that world. heraclitus does make occasional references to consciousness (see H. Diels, Die Fragmente der Vorsokratiker: Griechisch und Deutsch, ed. W. Kranz, 3 v. [8th ed. Berlin 1956]; v. 1 [10th ed. Berlin 1960–61], frgs 1, 110, 117). socrates mentions an experience of himself, recorded by Plato in the Phaedo (98B). plato himself speaks of self-awareness in the Charmides (164D–165B, 167A, 169D), in the Philebus (31A–33E, 43AB), and in the Theaetetus (185DE, 197BC). Aristotle is more concerned with the subject, notably with sense consciousness as an act of the sensus communis (Anim. 425B 12). plotinus refers to consciousness in the Enneads (1.4.10–11).

Among Christian writers of the Middle Ages there is fuller discussion. St. augustine treats of consciousness in De Trinitate (10.10.14), Soliloquies (2.1.1), and notably in the Confessions (10.8–27), where he speaks of plunging into the depths of his own being. Mention of it can be found also in the writings of matthew of aqua-sparta, richard of saint-victor, roger marston, peter john olivi, and especially St. thomas aquinas.

Sense Consciousness. Human knowledge may be divided into two kinds: sense knowledge, which man possesses in common with other animals; and intellectual knowledge, which is found in the human species alone. On the sense level man is said to have sense consciousness, or as it is sometimes called, animal consciousness. This, however, is not consciousness in the scholastic definition of the term, since consciousness is reflective knowledge, i.e., knowledge in which the knower, through his knowing power, knows himself in his own act. Such is not the case with sense knowledge, in general. For example, the external senses are aware only of other objects, not of themselves or of their own operation. Thus the operation of the external senses, while an act of cognition, is not one of consciousness. On the other hand, a type of sense consciousness, although called such only improperly, is found in the operation of the central sense (sensus communis ); this internal sense, when activated by the external senses, becomes aware of their operations. The central sense collects various contents received through the external senses into one common content, which it then refers to one and the same sensing subject.

Intellectual Consciousness. This is consciousness in the more proper meaning of the term. St. Thomas observes that the mind apprehends itself and is aware of its existence in its acts (De ver. 10.8). This intellectual awareness, in the terminology of later commentators, may be either direct (sometimes called concomitant), or reflex. Direct consciousness is that by which man primarily knows some object, and secondarily, in the act of knowing that object, knows his act of knowledge and himself as the knower. Reflex consciousness is the knowing act in which the mental act itself becomes an object of knowledge.

Different degrees of intensity characterize various states of direct consciousness. In some cases the knower may be so completely absorbed in the object known that, for all practical purposes, he loses awareness of himself as knower. On the other hand, when it is difficult to fix attention on an object, the intense effort involved ordinarily makes the knower more aware of himself. Since direct consciousness always implies at least marginal awareness of a mental state in reference to the self, every state of intellectual consciousness involves some degree of direct consciousness. But it is in reflex consciousness, where the knower deliberately considers his own mental states and himself as objects, that he becomes more completely aware of himself as a person. Consciousness of this kind is found only in man. Some brute animals are aware both of an external object and of an internal state, such as pleasure or pain, but give no acceptable evidence that they distinguish between such feeling and themselves as subjects undergoing it.

Other Internal Acts. Intellectual consciousness is related to freedom of choice. The latter requires that the one choosing be aware of a goal and that he recognize this as an end related to himself. Furthermore, the greater the number of objects of which he may be conscious, the wider the range of objects among which he may choose.

Acts of reflection, in which the knower turns inward upon himself, are often distinguished from acts of attention, in which the mind turns outward toward objects. Strictly speaking, an opposition should not be set up between these operations, since reflection may well be described as an act of attention to one's own mental processes. Nor should attention, as such, be confused with consciousness, because an individual experiencing a series of mental states may attend to the one that, at that time, is faintest in the field of consciousness. Nor should attention be confused with a voluntary act. While an act of attention may be voluntary, attention itself is a concentration of thought on some object, whereas a voluntary act is a choice to attend to an object. Furthermore, an act of attention need not always be preceded by a voluntary act. In the case of obsessions, for example, a person may attend to some object he wishes he could forget.

Consciousness has been so often identified with the self that some writers (e.g., William james) have described the self as a stream of consciousness. Self-consciousness is not the self, but it is a sign of the self. The person becomes aware of himself as a self by means of his conscious acts.

PSYCHOLOGICAL CONSCIOUSNESS

Whereas the term "consciousness" primarily means reflective awareness for the epistemologist, ordinarily it means simple awareness for the psychologist. Thus it is a generic term applicable to any cognitive or appetitive mental state.

Consciousness. Consciousness is not something distinct from the mental state called conscious. Awareness is the point of distinction between the vegetal and animal kingdoms. In many cases it is extremely difficult to determine whether a living organism is a plant or animal; but the problem in such cases is to discover enough evidence indicating whether or not the organism has at least some rudimentary awareness. Even human beings, capable as they are of a high degree of consciousness, experience different intensities of consciousness at different times. At one time there may be intense concentration of attention on the self whereas at others the diminished consciousness of sleep or twilight zones may intervene.

Subconscious and Unconscious. If consciousness is defined broadly as a state of awareness, it may be contrasted with subconsciousness and unconsciousness, which are states where awareness is lacking. The term "subconscious" usually refers to contents of the mind that are not at the same time in the field of consciousness but are on the threshold. That is to say, if someone is entertaining a train of thought, the next thought that will arise in consciousness, but has not yet appeared, is said to be subconscious. Subconsciousness is sometimes used also as a term referring to marginal states of consciousness. Unconsciousness usually refers to a lack of awareness of those contents of the mind that, at the time, are outside the field of consciousness and beyond the realm of the subconscious.

Freud's Usage. Freudian terminology makes use of two terms, "preconscious" and "unconscious," which are partly equatable with subconscious and unconscious as explained above. The preconscious (Pcs.), in psychoanalysis, refers to what have been called the contents of the subconscious and those unconscious contents of an individual's mind that he himself can raise out of his own mind without resort to psychoanalysis. This does not mean that the contents of the preconscious are always raised without effort; the important factor is that they can be raised by the individual himself. The unconscious (Ucs.), in Freudian terminology, refers to unconscious contents of an individual's mind that are not only out of the field of his awareness but that he cannot bring into awareness without the special techniques of psychoanalysis. These are repressed contents from the individual's own past and the residue of the racial unconscious.

Bibliography: m. stock, "Sense Consciousness According to St. Thomas," Thomist 21 (1958) 415–486. g. pedrazzini, Anima in conscientia sui secundum S. Thomam (Rome 1958). l. lavelle, La Conscience de soi (Paris 1963). j. m. hollenbach, Sein und Gewissen (Baden-Baden 1954). l. klages, Vom Wesen des Bewusstseins (4th ed. Munich 1955).

[p. nolan]

MODERN PHILOSOPHICAL THOUGHT

There is no question but that the modern transformation of the notion of consciousness began with René des cartes. A second stage of development can be distinguished with Immanuel Kant and a third with the phenomenological movement in the 20th century.

Descartes. In his search for an Archimedean point of certitude, Descartes retreated into the "interior world" until he discovered, in the famous cogito ergo sum, that while the object of consciousness might be wholly illusory, the consciousness itself is indubitable. Even if I am deceived by what I seem to be conscious of—even if there is no world and I have no body—that I must be in order to be thus deceived is certain. But it was not this bedrock truth (which St. Augustine had already noted) that made Descartes's discovery so important for the course of modern philosophy. It was rather the way in which he conceptualized and articulated it.

First, he understood the presence of the ego to itself in reflection to be the fundamental dimension of all experience. It is into the theater constituted by self-consciousness that all other objects of awareness are introduced as data: perceptions, images, ideas. This image of observing (clearly and distinctly) was rendered by Descartes in terms of cogitare and the scholastic-derived terminology of "objective existence." All modes of consciousness are assimilated to the cognitive: "willing, imagining, feeling, etc…. agree in falling under thedescription of thought, perception or consciousness."

Second, Descartes understood the thinking ego, the res cogitans, to be identical with the thought-of ego, the res cogitata. This identity of the subject and object of self-consciousness, this accessibility of the subject through objective knowledge, makes possible a science of the soul that assimilates reflection to introspection and, in contrast to the classical tradition, takes the nature of the soul to be more certainly known than perceptual objects.

In developing the theory that perceptions are contents of consciousness, the British empiricists were led to conclude, with David hume, that, if the self is the "theater" in which perceptions present themselves, it cannot itself be perceived or presented. Thus there is, in Hume's words, "no such idea," i.e., no perception of the self. It remained for Immanuel Kant to escape from this aporia, and to place the analysis of consciousness on a new path.

Kant. Kant agreed with Hume that the subject, who is the ground of objectivity qua that to which all objects are given, cannot himself be an object, i.e., be cognized directly. But man can know that there must be a subject, because how else would the course of his life and experience be unified? How else could the chaos of sensory impressions be organized into the wholes of everyday life? "The synthetic proposition that all of the variety of empirical consciousness must be combined in one single self-consciousness is the absolutely first and synthetic principle of our thought in general." This unifying function of consciousness Kant called the "transcendental unity of apperception" (see transcendental [kant ian]).

Kant argued that what is given in self-consciousness is not the subject as he is in himself, but the subject as object, i.e., as organized and subsumed under the categories of objectivity. Thus known, the subject can be material for a science of psychology. Such a science will be an inductive, introspective study of the "empirical ego," but not of the "transcendental ego." Hence, Kant concluded, there is self-certainty in consciousness (the "I think") but no self-knowledge. It is only the self as determined and not the self as determining that is accessible to reflection.

What was left as the unknowable nature of the self by Kant was deciphered by the idealists who followed him as the trans-personal character of the transcendental ego. For G. W. F. hegel, man's finite self-consciousness becomes merely a finite mode of God's consciousness of Himself. It was primarily on religious grounds that S. A. Kierkegaard reasserted the irreducibility of the person: "The concept of guilt and sin posits precisely the single individual as the single individual." But he provided no ontological foundation for his notion of the individual consciousness, and it was not until the 20th century that his rebellion against the system acquired an ontology.

Phenomenology. The phenomenological movement denies the primacy of consciousness as cogito (Descartes) or Ich denke (Kant). Instead it stresses the "prereflective cogito." Whereas, for Descartes, feeling is the consciousness of organic changes and imagination is the consciousness of an image, J. P. Sartre insists that the feeling of hatred is not the consciousness of hatred; rather it is the consciousness of Paul as hateful. Similarly, one's imagining of Peter is not a consciousness of the image of Peter but a specific kind of awareness of Peter himself. Nor can the awareness of the subject of his own existence be defined by the thought he has of existing. The world and one's body are present, according to the existential phenomenologists, not as objects of consciousness or thought, but as constituent elements of one's living awareness. We must not say, writes Gabriel Marcel, that the world is given to me as existing, for given normally signifies presented to a subject, whereas this assurance of the world and myself is constitutive of what we call the subject. The conscious subject is not a gaze for which the world and things exist but a unified life that overflows its explicit knowledge of itself.

The radical schism between this view of consciousness and that of classical modern philosophy is apparent. The epistemological problem loses its primacy since there is no consciousness transparent to itself (as Descartes claimed), confronting its ideas and sensations in the inner world. The self is understood primarily in terms of its "ex-sistence" or ontological union with the world, rather than by the act of reflective self-consciousness in which it "stands back" (in thought) from that junction and views the world as object (see existentialism; phe nomenology).

Bibliography: s. strasser, The Soul in Metaphysical and Empirical Psychology (Pittsburgh 1957). j. d. collins, A History of Modern European Philosophy (Milwaukee 1954). a. chollet, Dictionnaire de théologie catholique, ed. a. vacant et al., 15 v. (Paris 1903–50; Tables générales 1951–) 3.1:1156–74. j. iverach, j. hastings, ed., Encyclopedia of Religion and Ethics, 13 v. (Edinburgh 1908–27) 4:49a–58b. a. guzzo and e. valentini, Enciclopedia filosofica, 4 v. (Venice-Rome 1957) 1:1255–70. g. siewerth, Lexikon für Theologie und Kirche, ed. j. hofer and k. rahner, 10 v. (2d, new ed. Freiburg 1957–65) 2:329–330. w. anz, Die Religion in Geschichte und Gegenwart, 7 v. (3d ed. Tübingen 1957–65) 1:1112–15. r. eisler, Wörterbuch der philosophischen Begriffe, 3 v. (4th ed. Berlin 1927–30) 1:207–220.

[f. j. crosson]

consciousness The twentieth-century British psychologist Stuart Sutherland once defined consciousness as ‘a fascinating but elusive phenomenon: it is impossible to specify what it is, what it does, or why it evolved. Nothing worth reading has been written about it.’ Consciousness is indeed hard to define, but most people have an intuitive idea of what it is. It encompasses two different concepts: the notion of a self, and the feelings of which the self is aware, especially qualia — our raw sensory experiences.

Although some philosophers (panpsychists) have believed that all things, including inanimate objects such as chairs and umbrellas, are conscious, most people agree that consciousness is associated with brains (and, some would argue, with inanimate machines that work, in some crucial respect, like brains). Stated simply, then, the problem is how does the activity of nerve cells in the brain give rise to our subjective mental life? Neurons — specks of jelly in the brain, with their electrical impulses and their little squirts of neurotransmitter — seem so utterly different from the redness of red or the flavour of Marmite on toast.

The riddle of qualia is best illustrated with a thought experiment. Imagine a neuroscientist in some future century, who has complete knowledge of the workings of the brain — including the mechanisms of colour vision — but who happens to be colour blind and cannot herself distinguish between red and green. She uses the latest scanning techniques to generate a total description of all the electrical and chemical events in the brain of a normal human as he looks at a red object. The functional account may seem complete, but how could it be so without an explanation of the nature of the unique experience of red, which the scientist herself has never had? There is a deep epistemological gulf between descriptions of physical events in the brain and the personal, subjective experiences that we presume to be associated with those events.

Is consciousness a property of the entire brain — does it ‘emerge’ when the brain reaches a certain level of complexity? Or are only some parts of the brain conscious? (After all, if we argue that only brains and not other organs are conscious, why not imagine that only some parts of the brain are involved?) Indeed, neurological evidence suggests that we are unconscious of most of the activity in our brains — not just the below-stairs business of running the heart, digestion, posture, and so on, but also the pre-perceptual processing of information from the senses, and the complex task of selecting and controlling the individual muscles that carry out actions.

A rare disorder, aptly called ‘blindsight’, strikingly demonstrates a dissociation between conscious and unconscious visual processing. It results from damage restricted to the primary visual cortex in the cerebral hemispheres, which classically causes ‘cortical blindness’ in a corresponding part of the visual field. Although the patient denies seeing, say, a small spot of light presented in the blind part of the field, he or she can fairly accurately point towards the spot. Moreover, if a moving spot or a line is shown, the patient can ‘guess’ the direction of movement or the angle of the line, all the time unaware that it exists! This amazing paradox is explained by the fact that there are two main pathways of interconnected nerve cells from the eyes and through the brain. One goes to the primary visual cortex, and on into the lower parts of the temporal lobe, which is responsible for the identification of objects and the laying down of personal memories. The other projects via the reflex visual centres of the midbrain (which control eye movements) and thence up to the parietal lobes of the cortex, where the information is used to guide hand movements. Since the latter pathway is still intact in the patient with blindsight, he or she can use it for reaching for the object. But the other pathway into the temporal lobe seems to be intimately involved in conscious perception. A more subtle dissociation can occur in patients who have extensive damage to the temporal lobe, which does not interfere with basic visual functions but can cause agnosia — an incapacity to distinguish consciously between different objects and shapes. However, such patients can correctly shape their hands to pick up different objects that they cannot perceptually distinguish. It is almost as though there is an unconscious ‘zombie’ inside the heads of such patients, ‘seeing’ the world and guiding the hands but not troubling consciousness with what it is doing.

Unconscious vision is not just a neurological anomaly — it occurs even in normal people. If you are driving a car while talking to the person next to you or on a mobile telephone, many parts of your brain are processing enormous amounts of visual information to enable you to negotiate the traffic. Yet little of it reaches consciousness so long as your attention is focused on the conversation. Interestingly, it is hard to imagine the opposite scenario — of having a conversation unconsciously while paying attention to the traffic. At any instant, we seem to be fully aware of only a minute fraction of the things that we could be aware of. As you stand chatting to a friend at a party, you are unaware of the content of the other conversations around you — unless you deliberately eavesdrop out of the ‘corner of your ear’. Equally, our embarrassingly poor ability to recall the detail of a visual scene if the lights are suddenly switched off indicates that we are genuinely aware of only a tiny fraction of the flood of information that pours into our brains from our eyes. Only the focus of current attention seems fully represented in our consciousness, in the sense that it can be remembered. This all suggests that there is a link between consciousness, attention, and memory, and also that we cannot use language creatively without being conscious.

This raises the so-called ‘Zombie problem’. If we are able to do so much without being aware of it, what purpose does consciousness serve, and how did it evolve? Imagine an unconscious zombie that looks exactly like a person and does all the things a conscious human does, but without being conscious. There seems to be nothing logically impossible about this. Indeed, we have no way of knowing, for sure, that machines, animals, or even other human beings are truly conscious in the way that we feel ourselves to be. Some philosophers, most notably Gilbert Ryle, have argued that concepts of mind, such as self and intention, are merely ‘category mistakes’ — muddles that arise from the misuse of language. Such virtuosic philosophical argument reinforces the ‘Zombie problem’, but is deeply unsatisfactory. We know that we are conscious. Indeed, as René Déscartes pointed out, knowing that we are aware is the only thing that we are really sure about — ‘cogito, ergo sum’.

In parallel with Ryle's attempt to explain away the ‘Ghost in the Machine’, the school of psychology called behaviourism also argued that consciousness does not (or need not) exist and that science should confine itself to an attempt to explain externally observable behaviour. To behavioural psychologists, it has indeed been valuable to view the brain objectively, merely seeking accounts of behaviour without the baggage of common-language concepts such as will, intention, and need. However, it is difficult for most people — even brain researchers — to accept the extreme notion of ‘eliminative materialism’, namely that words such as ‘love’, ‘want’, and even ‘red’ have the same logical status as the once universal but now arcane view that living things have some kind of ‘vital essence’, which distinguishes them from the inanimate world.

More intriguing is epiphenomenalism. Just as the shadow of a running horse appears to run along with it but plays no causal role in the running, consciousness may simply accompany certain brain events but not itself have a function. Can it really be true that when you feel that you are choosing to pick up a cup, it is not the conscious intention that initiates the picking up? In fact, there is growing evidence that our subjective impressions of events in the world and of our intended actions are a kind of post-hoc ‘commentary’ on things that have already happened. Disturbing though it is, our conscious lives may be a plausible but illusory tale, a translation of the zombie world into the domain of subjectivity. But why should we have such a self-deluding system in the brain? How did it evolve? What could its value be?

Faced with such philosphical conundrums, many neuroscientists, with Francis Crick as their standard-bearer, have argued that we should simply aim to define the ‘neural correlate of consciousness’ — the parts of the brain and the nature and activity of nerve cells that implement conscious states. Once we have a clear understanding of the neural activity that is both necessary and sufficient for subjectivity, perhaps many of the philosophic problems will disappear.

The pragmatic advantage of this approach is that it transforms consciousness into an empirical problem that is approachable experimentally. Instead of asking ‘What is consciousness?’, one asks ‘What parts of the brain are active, or in what special way are they active, when someone does something consciously?’ One experimental approach that is proving fruitful is to monitor the activity of different parts of the cerebral cortex (with microelectrodes in animals, or with imaging techniques in human beings) while the retinal image is unchanging but the content of consciousness changes. For instance, how does activity in the brain change as a person or animal shifts attention from one thing to another? What happens when they view ambiguous visual images that can appear, at one moment, to be one thing, but, at another instant, to be something else?

That other mysterious aspect of subjectivity — the feeling of ‘free will’ and intention — is more difficult to study. However, fingers of evidence point towards the anterior cingulate cortex, a region on the inner surface of the frontal lobe. Patients with damage here sometimes feel that their own actions occur without being intended — alien hand syndrome. Conversely, they may be fully conscious but feel that they don't want to do anything at all — akinetic mutism.

The early decades of the twenty-first century will undoubtedly see great advances in our understanding of the neural correlate of consciousness. What is less certain is whether such empirical observations will take us any closer to resolving what philosopher David Chalmers has called the ‘Hard Problem’, that is, what really is the nature of subjectivity? We may be forced to admit that consciousness, like infinity and the particle-wave concepts in quantum mechanics, is a property that cannot be made intuitively straighforward. Consciousness, like gravity, mass, and charge, may be one of the irreducible properties of the universe for which no further account is possible.

V. S. Ramachandran, and Colin Blakemore

Bibliography

Churchland, P. M. (1996). The engine of reason, the seat of the soul. MIT Press, Cambridge MA.
Crick, F. H. C. (1993). The astonishing hypothesis. Charles Scribner, New York.
Ramachandran, V. S. (1998). Phantoms in the brain. William Morrow, New York.
Searle, J. (1994). The rediscovery of the mind. MIT Press, Cambridge MA.
Weizkrantz, L. (1986). Blindsight. Oxford University Press.

CONSCIOUSNESS

Something is conscious if there is something that it is like to be that thing. This widely accepted definition, proposed by philosopher Thomas Nagel (1974, reprint 1997 p. 519), emphasizes the subjective character of conscious experience, which is the fundamental obstacle to its scientific investigation. Scientists have no objective access to conscious states (even their own) so consciousness can only be studied scientifically by indirect means, and some believe that a complete scientific description of the world can and should be made without reference to consciousness at all. However to exclude conscious decisions from the causal chain of events would undermine all ethical and legal systems based on personal responsibility for consciously willed actions.

In the 1980s, neurophysiologist Benjamin Libet showed that when subjects were asked to make a voluntary movement at a time of their own choosing, brain activity initiating the movement (the readiness potential) routinely preceded by about half a second the conscious decision to make the action. Many people interpreted this as scientific proof that conscious choice and freewill are illusory, which would fit with the view that the physical universe is causally closed and deterministic. Libet himself safeguards personal freedom of action by arguing that although the brain's non-conscious readiness potential initiates an action, there is still time for the conscious mind to monitor and abort the process before the action is carried through.

Libet's work was an early example of scientific research into consciousness that combines objective information about brain activity with subjective reports from experimental subjects concerning their conscious states. Earlier generations had been handicapped by the need to choose between subjective and objective methods. Typical of these were introspectionism, pioneered by German psychologist Wilhelm Wundt (1832–1920), which depended on individuals analyzing their subjective thoughts, feelings, and perceptions into thousands of basic mental sensations, and the behaviorism of John Watson (1878–1958) and his successor B. F. Skinner (1904–1990). Watson rejected introspection, maintaining that if psychologists wanted to be real scientists they must study objective, verifiable data, which meant observable behavior. Such was his influence that consciousness was effectively banned from psychology for half a century in the mid-1900s.

The scientific study of consciousness was rehabilitated in part by new technologies that allowed the working of the brain to be objectively studied while mental processes were being carried out. The electroencephalogram (EEG), recording electrical activity in the brain, was available from the 1930s and used by Libet among others. Brain scanning techniques such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI), developed in the 1980s and 1990s, enabled detailed observation of active areas of the brain at work and confirmed the hypothesis that mental states are closely related to the physical condition of nerve cells (neurons). Neuroscientists were now able to observe the areas of neural activity associated with particular conscious experiences reported by human subjects, or deduced from the behavior of animals such as monkeys. Various systems in the brain were investigated, from individual cells to large networks and pathways of interconnected neurons, in the quest to identify possible neural correlates of consciousness (NCCs).

The exact relationship between conscious experience and the physical brain, and how and why some brain processes are conscious at all, is the core dilemma. David Chalmers, Director of the Center for Consciousness Studies at the University of Arizona at Tucson, has dubbed it the Hard Problem. In the mid-twentieth century the influential Oxford philosopher Gilbert Ryle (1900–1976) dismissed Descartes's dualist concept of mind-body relation as the ghost in the machine, and opened the way for various materialist accounts of consciousness. By the turn of the millennium most consciousness researchers embraced some form of non-reductive materialism, which holds that mental states are wholly caused by the physical brain, but have some quality over and above the sum of their molecular components. Variations on this theme include property dualism (mental states exist as properties of underlying physical states), dual aspect monism (the mental and the physical are two ways of looking at a single underlying reality), emergentism (consciousness emerges at a certain level of complexity), and panpsychism (every material object has an actual or potential degree of consciousness).

Treating consciousness as a real aspect of the physical world brings it back into the realm of scientific inquiry and removes the suggestion that it is an epiphenomenon, lying outside the causal nexus of the universe. But it does not automatically refute the claim that free choice and moral responsibility are delusions. The physical world of which consciousness is a part still appears to be deterministic, at least according to classical physics. Researchers into artificial intelligence, for instance, have drawn parallels between neuronal activity in brains and the processing of information in computers The question of whether the conscious mind itself is computational, that is, completely describable mathematically and therefore in deterministic terms, is hotly disputed.

Deterministic views are challenged within science by evidence from quantum physics, although its relevance is disputed and some of the claims speculative. For example, Oxford mathematician Roger Penrose proposes that in certain special conditions, found in the microtubules within brain cells, quantum systems provide the physical mechanism that brings about noncomputational conscious events. From a different starting point, Berkeley physicist Henry Stapp argues that quantum theory can explain how consciousness plays a creative role in shaping events and creating the world as humans know it. These views are frequently criticized, but at the very least, quantum theory puts a large question mark over the old assumption that the universe is a collection of objective facts that are (in theory at least) completely knowable.

Consideration of the ethical questions posed by the investigation and manipulation of consciousness falls under the sub-discipline of neuroethics. But the challenge to produce an account of conscious experience that provides an adequate basis for morality at all, and is at the same time both philosophically and scientifically robust, lies at the heart of all consciousness studies.

ANTHONY FREEMAN

SEE ALSO Artifical Intelligence;Decartes, RenéEmotion;Emotional Intelligence;Neuroethics;Robot Toys.

BIBLIOGRAPHY

Chalmers, David J. (1996). The Conscious Mind: In Search of a Fundamental Theory. New York: Oxford University Press. A technical book, written by a philosopher making use of scientific research, mostly accessible to the general reader. The stance is non-reductive physicalism.

Dennett, Daniel. (2003). Freedom Evolves. New York: Viking Press. A representative title from many by this popular philosopher of mind. Written from a reductive viewpoint for both professional and general readers.

Freeman, Anthony. (2003). Consciousness: A Guide to the Debates. Santa Barbara, CA: ABC-CLIO. A non-technical introduction that includes extracts from classic texts.

Libet, Benjamin; Anthony Freeman; and Keith Sutherland, eds. (1999). The Volitional Brain: Towards a Neuroscience of Freewill. Exeter, UK: Imprint Academic. Collected essays by scientists and philosophers.

Nagel, Thomas. (1974). "What Is It Like to Be a Bat?" Philosophical Review 83(4): 435–450. Reprinted in the 1997 book The Nature of Consciousness: Philosophical Debates, eds. Ned Block, Owen Flanagan, and Güven Güzeldere. Cambridge, MA: MIT Press. A seminal paper raising the need for philosophers to address subjectivity.

Popper, Karl, and John Eccles. (1983). The Self and Its Brain: An Argument for Interactionism. London: Routledge. Two eminent authors make the case for the unfashionable dualist approach to mind-body interaction.