A response to John Searle's review of my book in the New York Review of Books, March 6, 1997. This appears as a letter in NYRB, May 15, 1997. Searle responded; my more detailed response in turn is also online.
In my book The Conscious Mind, I deny a number of claims that John Searle finds "obvious", and I make some claims that he finds "absurd". But if the mind/body problem has taught us anything, it is that nothing about consciousness is obvious, and that one person's obvious truth is another person's absurdity. So instead of throwing around this sort of language, it is best to examine the claims themselves and the arguments that I give for them, to see whether Searle says anything of substance that touches them.
The first is my claim that consciousness is a nonphysical feature of the world. I resisted this claim for a long time, before concluding that it is forced on one by a sound argument. The argument is complex, but the basic idea is simple: the physical structure of the world - the exact distribution of particles, fields, and forces in spacetime - is logically consistent with the absence of consciousness, so the presence of consciousness is a further fact about our world. Searle says this argument is "invalid": he suggests that the physical structure of the world is equally consistent with the addition of flying pigs, but that it does not follow that flying is nonphysical.
Here Searle makes two elementary mistakes. First, he gets the form of the argument wrong. To show that flying is nonphysical, we would need to show that the world's physical structure is consistent with the absence of flying. From the fact that one can add flying pigs to the world, nothing follows. Second, the scenario he describes is not consistent. A world with flying pigs would have a lot of extra matter hovering meters above the earth, for example, so it could not possibly have the same physical structure as ours. Putting these points together: the idea of a world physically identical to ours but without flying, or without pigs, or without rocks, is self-contradictory. But there is no contradiction in the idea of a world physically identical to ours without consciousness, as Searle himself admits.
The underlying point is that the position of pigs - and almost everything else about the world - is logically derivable from the world's physical structure, but the presence of consciousness is not. So to explain why and how brains support consciousness, an account of the brain alone is not enough; to bridge the gap, one needs to add independent "bridging" laws. One can resist this conclusion only by adopting a hard-line deflationism about consciousness. That path has its own problems, but in any case it is not open to Searle, who holds that consciousness is irreducible. Irreducibility has its consequences. Consistency requires that one face them directly.
The next issue is my nonreductive functionalism. This bridging law claims that systems with the same functional organization have the same sort of conscious experiences. My detailed argument for this claim is not recognizable in the trivial argument that Searle presents as mine and rebuts. The basic idea, presented in Chapter 7 of the book but ignored by Searle, is that if the claim is false, then there can be massive changes in conscious experience which a subject can never notice. (Searle's own position is rebutted on p. 258.) He also points to patients with Guillain-Barre syndrome as a counterexample to my claim, but this once again gets the logic wrong. My claim concerns functionally identical beings, so it is irrelevant to point to people who function differently. I certainly do not claim that beings whose functioning differs from ours are unconscious.
The final issue is panpsychism: the claim that some degree of consciousness is associated with every system in the natural world. Here Searle misstates my view: he says that I am "explicitly committed" to this position, when I merely explore it and remain agnostic; and he says incorrectly that it is an implication of property dualism and nonreductive functionalism. One can quite consistently embrace those views and reject panpsychism, so the latter could not possibly function as a "reductio ad absurdum" of the former. I note also that the view which I describe as "strangely beautiful", and which Searle describes as "strangely self-indulgent", is a view I reject.
I do argue that panpsychism is not as unreasonable as is often supposed, and that there is no knockdown argument against it. Searle helps confirm the latter claim: while protesting "absurdity", his arguments against panpsychism have no substance. He declares that to be conscious, a system must have the right "causal powers", which turn out to be the powers to produce consciousness: true, but trivial and entirely unhelpful. And he says that simple systems (such as thermostats) do not have the "structure" required for consciousness; but this is precisely the claim at issue, and he provides no argument to support it (if we knew what sort of structure were required for consciousness, the mind-body problem would be half-solved). So we are left where we started. Panpsychism remains counterintuitive, but it cannot be ruled out at the start of inquiry.
In place of substantive arguments, Searle provides gut reactions: every time he disagrees with a view I discuss, he calls it "absurd". In the case of panpsychism (a view not endorsed by me), many might agree. In other cases, the word is devalued: it is not even surprising, for example, that mental terms such as "perception" are ambiguous between a process and a subjective experience; and given that a trillion interacting neurons can result in consciousness, there is no special absurdity in the idea that a trillion interacting silicon chips or humans might do the same. I do bite one bullet, in accepting that brain-based explanations of behavior can be given that do not invoke or imply consciousness (although this is not to say that consciousness is causally irrelevant). But Searle's own view on irreducibility would commit him to this view too, if he could only draw the implication.
Once we factor out mistakes, misrepresentations, and gut feelings, we are left with not much more than Searle's all-purpose critique: "the brain causes consciousness". Although this mantra (repeated at least ten times) is apparently intended as a source of great wisdom, it settles almost nothing that is at issue. It is entirely compatible with all of my views: we just need to distinguish cause from effect, and to note that it does not imply that only the brain causes consciousness. Indeed, Searle's claim is simply a statement of the problem, not a solution. If one accepts it, the real questions are: Why does the brain cause consciousness? In virtue of which of its properties? What are the relevant causal laws? Searle has nothing to say about these questions. A real answer requires a theory: not just a theory of the brain, but also a detailed theory of the laws that bridge brain and consciousness. Without fulfilling this project, on which I make a start in my book, our understanding of consciousness will always remain at a primitive level.
David Chalmers
University of California, Santa Cruz
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