The Conscious Mind: In Search of a Fundamental Theory. By David J. Chalmers. Oxford University Press. 414 pp. $29.95.
Reviewed by Stephen M. Barr
Physics cannot explain why an apple looks red. This will surprise some people, but it is a fact that can hardly be disputed. Physics does indeed tell us why an apple reflects red light and what red light is—an electromagnetic wave whose wavelength is between 620 and 700 nanometers. Biophysics can explain why different wavelengths of light affect certain retinal cells differently, and thus how the brain can tell one color of light from another.
But what is left to explain is why the apple looks red, the sensual experience of redness. Why is it that when I see light of 650 nanometers I do not experience the sensation of shocking pink or pale yellow, rather than red? Indeed, if mechanical devices can distinguish wavelengths of light without having sensations, then why do I experience any sensation at all?
This is what philosophers nowadays call the problem of "qualia." Physics deals exclusively with quantities: The equations of theoretical physics allow one to calculate only quantities, and the devices of experimental physics measure only quantities. But since one cannot reduce to numbers what it is like to have a toothache or a paper-cut, to taste licorice or smell a lilac, to hear a flute or fingernails on a chalkboard, it is impossible that these subjective experiences, these qualia, can be derived from any equation. As Erwin Schrödinger put it, "[While] all scientific knowledge is based on sense perceptions, the scientific views of natural processes formed in this way lack all sensual qualities and therefore cannot account for the latter."
This problem of qualia is an important part of the larger "problem of consciousness" that is receiving increasing attention from both philosophers and scientists. Most scientific materialists, however, remain unable to admit that there is any problem whatever. Their dogma that all of reality is expressed in physics forces them to declare that anything about subjective experience underivable from physics must be unreal. The attitude of Niels Bohr is typical: "The question of whether [a] machine really feels or ponders, or whether it merely looks as though it did, is of course absolutely meaningless."
This view of reality leads to various behavioristic conceptions of the mind. In the "logical behaviorism" of Gilbert Ryle, the mind is analyzed in terms of dispositions to behave in certain ways. In the less crude "functionalism" put forward in the 1960s, internal mental states—though acknowledged to exist—are defined in terms of their role in causing behavior: produced by certain stimuli, they interact with other internal states and tend to lead to certain behavior. There is nothing in all of this that cannot be applied to the internal states of a computer, or indeed of a microwave oven.
To the extent that subjective experience is noticed at all by the modern materialist, it is dealt with—and eliminated—by the "identity theory," according to which mental states and brain states are the same. This is the reigning orthodoxy in modern cognitive science. In the words of the philosopher Hilary Putnam, "It is no longer possible to believe that the mind-body problem is a genuine theoretical problem, or that a ‘solution’ would shed the slightest light on the world in which we live."
David J. Chalmers, a young Australian-born professor of philosophy at the University of California-Santa Cruz has written a book saying that there really is a problem, that there really is something called consciousness, and that we really do not have even the beginnings of a theoretical understanding of it. His book has attracted considerable attention both within the academic world and in the popular press. That this should be so when he is merely arguing for something transparently obvious may seem odd, but we should be thankful, for we live in an age when the obvious has few partisans.
Chalmers accepts a great deal of the current orthodoxy. He has no doubt that a mechanistic account can be given of all of the behavioral "cognitive mind," including our capacity to understand and to will. He certainly does not believe in a spiritual component in man. He does believe, however, that missing from the physicalist picture is the "phenomenal mind": the realm of subjective experience and its sensual aspects, the qualia.
Building on the arguments of many philosophers, notably Frank Jackson and Saul Kripke, Chalmers makes the case very powerfully that physical science cannot explain qualia. He is forced, against his own admitted predispositions, to reject materialism and embrace what he dubs a "naturalistic dualism." What makes his dualism naturalistic, he says, is that he posits no "transcendental element" (by which he probably means a soul or spirit). He believes that behavior can be entirely explained physically, and he thinks that consciousness can be naturally, though not physically, explained.
Chalmers makes some advance beyond people like Roger Penrose who suggest merely that consciousness cannot be explained by the presently known laws of physics: No physical laws, Chalmers argues, could ever explain qualia. But his own "natural explanation" that consciousness will be explained by "psycho-physical laws" remains unclear. What might such psycho-physical laws look like? They cannot be equations, for then they would no more explain qualia than do the laws of physics. Indeed they would be, in effect, just additional laws of physics. Indeed, there is a question of whether it makes sense even to talk about a "theory" of qualia: If a theory is something by which we understand, and a sensation something we feel, how can a theory ever capture sensation?
Chalmers creates an even greater difficulty for himself by his belief that all of behavior can be understood physically. He has to believe this because he takes it to be a fact that "the physical domain is causally closed" and therefore cannot be influenced by anything that lies outside of physics, such as the "phenomenal mind." For him, consciousness is entirely passive, and he believes he thereby escapes the well-known conundrums of "interactionist dualism."
He ends up, however, in a worse bind, for writing this book was a form of behavior, and there is no way, in his scheme, that his "phenomenal mind"—his experiences of qualia, his consciousness—can have had any influence on what his fingers typed. Indeed, they can have no influence on what he believes about consciousness, since belief for him lies in the behavioral and physically determined "cognitive mind." To put it bluntly, if his non-interactionist dualism is right then he cannot know anything about consciousness and we cannot learn about it by reading his book. He struggles unsuccessfully with this problem:
One might conclude that the physical portion of me (my brain, say) is not justified in its belief [that I am conscious]. But the question is whether I am justified in my belief, not whether my brain is justified in its belief; . . . there is more to me than my brain. I know I am conscious, and the knowledge is based solely upon my immediate experience.
He may know more than his brain, but according to Chalmers’ own theory it is his brain that wrote the book. Indeed, his brain wrote those sentences, and I wonder how it wrote so knowledgeably about all the things that Chalmers knows and his brain does not.
The truth is that Chalmers need not have gotten into this predicament, for the physical world is not "causally closed." For example, no physical reason can be given why a radioactive nucleus decays at this moment rather than that. Chalmers is fully conversant with the ideas of quantum theory, and so he hedges at one point: "The physical world is more or less causally closed, in that for any given physical event it seems there is a physical explanation ([leaving aside] a small amount of quantum indeterminacy)." The effects of quantum indeterminacy, however, are not necessarily small. In fact, the argument should be turned around, and was in an excellent article by the philosopher and physicist Avshalom Elitzur in 1989. We know from arguments like Chalmers’ that consciousness is not explicable entirely by physics. But consciousness clearly affects behavior, and in particular the behavior of people who worry aloud whether their consciousness is explicable entirely by physics! And therefore the physical domain cannot be causally closed. (Though Elitzur himself does not think quantum indeterminacy provides the causal opening.)
The problem of qualia and of consciousness bears out an observation made by Monsignor Ronald Knox in The Hidden Stream, where he noted that the supernatural mysteries of faith involve realities about which there is already a mystery at the natural level:
It’s not surprising that there is a problem of free will in revealed theology, because there is a problem of free will in common or garden philosophy. The mystery comes in just where you would expect it to come in; where there is a mystery anyhow. The way I have tried to put it . . . is that you may picture human thought as a piece of solid rock, but with a crevice here and there—the places, I mean, where we think and think and it just does not add up. And the Christian mysteries are like tufts of blossom which seem to grow in those particular crevices, there and nowhere else.
Before the mysteries of the Trinity and the Incarnation there is already the mystery of personality. Before the mystery of the Real Presence there is already the mystery of appearance and reality. Before the mystery of spirit, there is the mystery of mind. Chalmers is unaware of supernatural mysteries. Indeed, he is blind even to the natural mysteries of human freedom and rationality. He is concerning himself with things on the much lower level of mere sensation, which we have in common with brutes. Yet even here there is an enigma.
In Knox’s words, qualia are something about which we "think and think and it just does not add up." Do the qualia pertain to the level of matter, in which case there is something about matter itself that escapes the laws of physics? Or do they pertain to spirit, in which case we should have to say that animals lack subjective experience? Or is there something between matter and spirit, above the merely physical, but below the rational? None of these ideas is easy to credit.
But whatever qualia are, they are real. And that alone tells us that simple-minded materialism cannot be right.
Stephen M. Barr is Associate Professor of Physics at the Bartol Research Institute, University of Delaware.