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По уговору с апачей привожу текст из вступления к книжке Дэвида Чалмерса The Conscious Mind. На сегодняшний день он входит в пятерку самых авторитетных авторов по теории сознания.
См. также: Davidson// Jaegwon Kim//Thomas Nagel//Searle//Dennett
David Chalmers
Two Concepts of Mind
1. What Is Consciousness?
Conscious experience is at once the most familiar thing in the world and the most mysterious. There is nothing we know about more directly than consciousness, but it is far from clear how to reconcile it with everything else we know. Why does it exist? What does it do? How could it possibly arise from lumpy gray matter? We know consciousness far more intimately than we know the rest of the world, but we understand the rest of the world far better than we understand consciousness.
Consciousness can be startlingly intense. It is the most vivid of phenomena; nothing is more real to us. But it can be frustratingly diaphanous: in talking about conscious experience, it is notoriously difficult to pin down the subject matter. The International Dictionary of Psychology does not even try to give a straightforward characterization:
Consciousness: The having of perceptions, thoughts, and feelings; awareness. The term is impossible to define except in terms that are unintelligible without a grasp of what consciousness means. Many fall into the trap of confusing consciousness with self-consciousness-to be conscious it is only necessary to be aware of the external world. Consciousness is 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. (Sutherland 1989)
Almost anyone who has thought hard about consciousness will have some sympathy with these sentiments. Consciousness is so intangible that even this limited attempt at a definition could be disputed: there can arguably be perception and thought that is not conscious, as witnessed by the notions of subliminal perception and unconscious thought. What is central to consciousness, at least in the most interesting sense, is experience. But this is not definition. At best, it is clarification.
Trying to define conscious experience in terms of more primitive notions is fruitless. One might as well try to define matter or space in terms of something more fundamental. The best we can do is to give illustrations and characterizations that lie at the same level. These characterizations cannot qualify as true definitions, due to their implicitly circular nature, but they can help to pin down what is being talked about. I presume that every reader has conscious experiences of his or her own. If all goes well, these characterizations will help establish that it is just those that we are talking about.
The subject matter is perhaps best characterized as "the subjective quality of experience." When we perceive, think, and act, there is a whir of causation and information processing, but this processing does not usually go on in the dark. There is also an internal aspect; there is something it feels like to be a cognitive agent. This internal aspect is conscious experience. Conscious experiences range from vivid color sensations to experiences of the faintest background aromas; from hard-edged pains to the elusive experience of thoughts on the tip of one's tongue; from mundane sounds and smells to the encompassing grandeur of musical experience; from the triviality of a nagging itch to the weight of a deep existential angst; from the specificity of the taste of peppermint to the generality of one's experience of selfhood. All these have a distinct experienced quality. All are prominent parts of the inner life of the mind.
We can say that a being is conscious if there is something it is like to be that being, to use a phrase made famous by Thomas Nagel.1 Similarly, a mental state is conscious if there is something it is like to be in that mental state. To put it another way, we can say that a mental state is conscious if it has a qualitative feel-an associated quality of experience. These qualitative feels are also known as phenomenal qualities, or qualia for short.2 The problem of explaining these phenomenal qualities is just the problem of explaining consciousness. This is the really hard part of the mind-body problem.
Why should there be conscious experience at all? It is central to a subjective viewpoint, but from an objective viewpoint it is utterly unexpected. Taking the objective view, we can tell a story about how fields, waves, and particles in the spatiotemporal manifold interact in subtle ways, leading to the development of complex systems such as brains. In principle, there is no deep philosophical mystery in the fact that these systems can process information in complex ways, react to stimuli with sophisticated behavior, and even exhibit such complex capacities as learning, memory, and language. All this is impressive, but it is not metaphysically baffling. In contrast, the existence of conscious experience seems to be a new feature from this viewpoint. It is not something that one would have predicted from the other features alone.
That is, consciousness is surprising. If all we knew about were the facts of physics, and even the facts about dynamics and information processing in complex systems, there would be no compelling reason to postulate the existence of conscious experience. If it were not for our direct evidence in the first-person case, the hypothesis would seem unwarranted; almost mystical, perhaps. Yet we know, directly, that there is conscious experience.The question is, how do we reconcile it with everything else we know?
Conscious experience is part of the natural world, and like other natural phenomena it cries out for explanation. There are at least two major targets of explanation here. The first and most central is the very existence of consciousness. Why does conscious experience exist? If it arises from physical systems, as seems likely, how does it arise? This leads to some more specific questions. Is consciousness itself physical, or is it merely a concomitant of physical systems? How widespread is consciousness? Do mice, for example, have conscious experience?
A second target is the specific character of conscious experiences. Given that conscious experience exists, why do individual experiences have their particular nature? When I open my eyes and look around my office, why do I have this sort of complex experience? At a more basic level, why is seeing red like this, rather than like thatl It seems conceivable that when looking at red things, such as roses, one might have had the sort of color experiences that one in fact has when looking at blue things. Why is the experience one way rather than the other? Why, for that matter, do we experience the reddish sensation3 that we do, rather than some entirely different kind of sensation, like the sound of a trumpet?
When someone strikes middle C on the piano, a complex chain of events is set into place. Sound vibrates in the air and a wave travels to my ear. The wave is processed and analyzed into frequencies inside the ear, and a signal is sent to the auditory cortex. Further processing takes place he;e: isolation of certain aspects of the signal, categorization, and ultimately reaction. All this is not so hard to understand in principle. But why should this be accompanied by an experience? And why, in particular, should it be accompanied by that experience, with its characteristic rich tone and timbre? These are two central questions that we would like a theory of consciousness to answer.
Ultimately one would like a theory of consciousness to do at least the following: it should give the conditions under which physical processes give rise to consciousness, and for those processes that give rise to consciousness, it should specify just what sort of experience is associated. And we would like the theory to explain how it arises, so that the emergence of consciousness seems intelligible rather than magical. In the end, we would like the theory to enable us to see consciousness as an integral part of the natural world. Currently it may be hard to see what such a theory would be like, but without such a theory we could not be said to fully understand consciousness.
Before proceeding, a note on terminology. The term "consciousness" is ambiguous, referring to a number of phenomena. Sometimes it is used to refer to a cognitive capacity, such as the ability to introspect or to report one's mental states. Sometimes it is used synonymously with "awakeness." Sometimes it is closely tied to our ability to focus attention, or to voluntarily control our behavior. Sometimes "to be conscious of something" comes to the same thing as "to know about something." All of these are accepted uses of the term, but all pick out phenomena distinct from the subject I am discussing, and phenomena that are significantly less difficult to explain. I will say more about these alternative notions of consciousness later, but for now, when I talk about consciousness, I am talking only about the subjective quality of experience: what it is like to be a cognitive agent.
A number of alternative terms and phrases pick out approximately the same class of phenomena as "consciousness" in its central sense. These include "experience," "qualia," "phenomenology," "phenomenal," "subjective experience," and "what it is like." Apart from grammatical differences, the differences among these terms are mostly subtle matters of connotation. "To be conscious" in this sense is roughly synonymous with "to have qualia," "to have subjective experience," and so on. Any differences in the class of phenomena picked out are insignificant. Like "consciousness," many of these terms are somewhat ambiguous, but I will never use these terms in the alternative senses. I will use all these phrases in talking about the central phenomenon of this book, but "consciousness" and "experience" are the most straightforward terms, and it is these terms that will recur.
2. The Phenomenal and the Psychological Concepts of Mind
Conscious experience is not all there is to the mind. To see this, observe that although modern cognitive science has had almost nothing to say about consciousness, it has had much to say about mind in general. The aspects of mind with which it is concerned are different. Cognitive science deals largely in the explanation of behavior, and insofar as it is concerned with mind at all, it is with mind construed as the internal basis of behavior, and with mental states construed as those states relevant to the causation and explanation of behavior. Such states may or may not be conscious. From the point of view of cognitive science, an internal state responsible for the causation of behavior is equally mental whether it is conscious or not.
At the root of all this lie two quite distinct concepts of mind. The first is the phenomenal concept of mind. This is the concept of mind as conscious experience, and of a mental state as a consciously experienced mental state. This is the most perplexing aspect of mind and the aspect on which I will concentrate, but it does not exhaust the mental. The second is the psychological concept of mind. This is the concept of mind as the causal or explanatory basis for behavior. A state is mental in this sense if it plays the right sort of causal role in the production of behavior, or at least plays an appropriate role in the explanation of behavior. According to the psychological concept, it matters little whether a mental state has a conscious quality or not. What matters is the role it plays in a cognitive economy.
On the phenomenal concept, mind is characterized by the way it feels; on the psychological concept, mind is characterized by what it does. There should be no question of competition between these two notions of mind. Neither of them is the correct analysis of mind. They cover different phenomena, both of which are quite real.
I will sometimes speak of the phenomenal and psychological "aspects" of mind, and sometimes of the "phenomenal mind" and the "psychological mind." At this early stage, I do not wish to beg any questions about whether the phenomenal and the psychological will turn out to be the same thing Perhaps every phenomenal state is a psychological state, in that it plays a significant role in the causation and explanation of behavior, and perhaps every psychological state has an intimate relation to the phenomenal. For now, all that counts is the conceptual distinction between the two notions what it means for a state to be phenomenal is for it to feel a certain way. and what it means for a state to be psychological is for it to play an appropriate causal role. These distinct notions should not be conflated, at least at the outset.
A specific mental concept can usually be analyzed as a phenomenal concept, a psychological concept, or as a combination of the two. For instance, sensation, in its central sense, is best taken as a phenomenal concept: to have a sensation is to have a state with a certain sort of feel. On the other hand, the concepts of learning and memory might best be taken as psychological. For something to learn, at a first approximation, is for it to adapt its behavioral capacities appropriately in response to certain kinds of environmental stimulation. In general, a phenomenal feature of the mind is characterized by what it is like for a subject to have that feature, while a psychological feature is characterized by an associated role in the causation and/or explanation of behavior.
Of course, this usage of the term "psychological" is a stipulation: it arises from identifying psychology with cognitive science as described above. The everyday concept of a "psychological state" is probably broader than this, and may well include elements of the phenomenal. But nothing will rest on my use of the term.