Physicalism has never held any appeal for me. ‘It is false that the mind is non-physical’ seems to me plainly false. It seemed obvious to me, even as a student, that physicalism must be false, if it is taken to be the view that there is nothing outside the things described by physics. Obviously there is a difficulty for physicalism here. At which time in its history are we to take the authority of physics about what there is? Not so long ago physics told us that there was no first event, for example, and that there was such a thing as a steady state for the expanding universe. Now we know that both propositions are false.
I have always been more interested, however, not in such details but in the systematic way in which physicalism restricts our ontology, if it does, in the interests of unified explanation. The most obvious restriction is on the mind as such. The physicalist wants to replace the mind and mental states in our theories with a physical entity and physical states. The central state materialist, for example, tells us that the mind is the relevant part of the brain and that mental states are brain states, nothing more. (Of course, since identity is commutative, it also follows that all brain states are mental states, perhaps not quite what is wanted: idealism!) But now we are missing phenomenal properties or qualia. Why would anyone want to endorse a theory of this sort? Leibniz argued for harmony in his sense: a maximum complexity of phenomena consistent with a minimum underlying complexity of explanatory law. Why would anyone sacrifice so many phenomena – all of the phenomena, in fact, in the sense of everything that appears! – for a set of laws and principles which doesn’t even mention them? It seems perverse.
So when in the late 1960s or so central state materialism was replaced by functionalism, it should perhaps have been anticipated that functionalism too would have difficulties with phenomenal properties or qualia. The mathematical and computer science glitz of functionalism blinded people, I think, until fairly recently. In retrospect it seems obvious that if we were probabilistic Turing machines, then we would not see colours or anything else. But we do. So we are not probabilistic Turing machines. Of course a lot of work is devoted to machine vision, and it is important and interesting, for example machine reading of bar codes, or image analysis, including optical character recognition. But do these things amount to vision in the sense in which human beings are said to see colours and other things? It would seem not. A machine vision system will work every bit as well even if it doesn’t see anything. So why is there any need to suppose that it does see anything?
And there you have the problem with all sorts of physicalism. All of them are consistent with the non-existence of the things they say are physical. You could have neurons firing away, and no qualia, no apprehension of phenomenal properties, nothing! You could have just a Chalmers-style zombie. Of course this is hotly disputed by the enemies of the zombies. These unfriendly philosophers say that if you have the right physical substrate, then the zombie must also be conscious, and so zombies are impossible.
The most extreme version of physicalism is eliminative materialism, which claims that our concepts having to do with mentality are defective in a way that ensures that they have no application at all. These concepts represent a folk psychology, every bit as bad in its way as folk tales and folk medicine. But really eliminative materialism is just the cleanest and most logical version of physicalism. Forget everything non-physical, because nothing non-physical exists. There are no minds, no beliefs, no hopes, no fears, no psychological states at all. Neurophysiology will give us better concepts and better classifications – we hope.
If this seems uncommonsensical, it is. I am aware of my mind working slowly, or quickly, or well, or badly, I apprehend my beliefs, I am aware of many of my hopes and fears, and cognizant of other psychological states as well. I know what I am thinking, and I know it pretty directly. So goes the view which I would take as the beginning of wisdom in the philosophy of mind. The physicalist can’t just cry down the elements in the world of which he disapproves, from an explanatory view, and hope to get away with it.
The history of twentieth-century philosophy of mind has been the history of the failure of physicalism. Behaviorism came first, and it missed mental states and phenomenal properties or qualia. In the face of overwhelming logical difficulties, and following up very natural lines of thought in psychiatry and neurophysiology, we got central state materialism. The logical difficulties of this view are also insuperable, but it didn’t matter, because before they could really register in the collective philosophical psyche we got functionalism. But here too the phenomena of mental life were pushed aside, in favor of a sort of high-powered behaviorism – what else is the Turing Test? And finally when all this became clear, and the jig was up, we got eliminative materialism, the logical conclusion of physicalism or materialism. Mental life is as much of a fiction is the life of witches and goblins. But really truly, is it? I think that we are pretty much where we began at the end of the nineteenth century and the beginning of the twentieth century. If this is right, and history repeats itself, can can expect a welcome period of introspectionism to add to the massive progress in physiology and psychology over the last hundred years, made all the stronger by a frank recognition of the failures of physicalism?