Today I would like to write about dualism and the origins of the mind-body problem. Dualism is of course a view that comes in quite a number of different forms, but Descartes’ form was two-way interactionist dualism. He himself did not allow the existence of the mind-body problem, much less discover or invent it. He wrote, in one of the Replies to Objections, that ‘The whole problem contained in such questions arises simply from a presupposition that is false and cannot in any way be proved, namely that, if the soul and the body are two substances whose nature is different, this prevents them from being able to act on each other’ [my italics]. Descartes’ actual role was to describe the mind and the body with their “principal attributes” so precisely that the mind-body problem was forced on the sharper of his readers, in particular Princess Elisabeth of Bohemia and Gassendi. It is to them that the discovery of the mind-body problem should be credited. But Descartes should share in their Nobel Prize (or maybe the Tang Prize, for the reign of the Tang Dynasty during which gunpowder, as distinct from Nobel’s dynamite, which is a high explosive, was invented), as Descartes did the groundwork in his very precise descriptions of the relevant elements: linear extension and consciousness. But Elisabeth was then able to write, ‘You utterly exclude extension from your notion of soul.’ The problem was that something that does not live in the world of linear extension cannot interact with it, because interaction involves effects (“propulsion”) or transfer of energy, and this in turn involves contact, which presupposes spatial location and therefore extension. There is also the question how something lacking linear extension can make its mark on something possessing linear extension. Gravity, it should be noted, does have position and linear extension; there’s a lot of it between the Earth and the Sun, and it weakens as you get further away from massive bodies. So by Descartes’ criterion gravity is full-bloodedly physical.
I have always liked dualism, except that it doesn’t work, for much the reasons Elisabeth and Gassendi gave. Dualisms today, such as E.J. Lowe’s, just cover up the problem. But there it is, lying in wait for the unwary, even those to whom David Duffy drew attention in his Comment yesterday, “who have been exposed to computers all their life”. The existence of computers might tempt these people to think that the mind-body problem can be solved by comparing the mind to the program and the brain to the hardware. The plain difficulty is that though the program is computational, it is straightforwardly physical in Descartes’ sense, the arguments of the early functionalists and today’s artificial intelligentsia notwithstanding. Even Stockfish, a program rated at 3378 (Magnus Carlsen is 2802), can’t yet think, even about chess, in any interesting sense other than “compute”.
The reason, I think, that I rather like dualism is that it does preserve the distinction between the psychological and the physical. There is a big difference between saying that something is red, and something reflects light of a dominant wavelength of 6.5 x 10-5 cms. There just is such a difference. And differences of this sort seem to remain, whatever the physical description is. It doesn’t have to be dominant wavelength, which is anyway a psychological concept. It could be something behavioural. But all such descriptions are consistent with the absence of red. You could have something that satisfied them and yet there is no red anywhere near that thing. So far so good, but this is just a claim about phenomenal properties, things like colours, or sounds, or heat, and so on. Some philosophers, like me, call the phenomenal properties “qualia”, but others reserve the term for properties of experience itself, so that it is false that apples are red, but true that experiences are. We have here something that doesn’t help much with the mind-body problem, except that our solution to the mind-body problem, must respect the distinction between the physical and the phenomenal.
On the other hand the various forms of dualism are hard to believe. Interactionist dualism doesn’t give a satisfactory account, of all things, of interaction! This is where the generation of philosophers right after Descartes realized that in spite of his enormous contribution, he had got things wrong. And so this generation of philosophers, remaining true to dualism, tried non-interactionist forms, such as occasionalism, and the pre-established harmony. There is a form of dualism that I think has not received enough press, and I’m not sure what it should be called, but “correlationism” suggests itself. There are certain neurons firing in the visual cortex, say, and then there are sensations of red. When we have one set of events, it is followed by the other set. This is a form of interactionism, I suppose, but with the causality really stripped down to its Humean essentials. You could easily write it with INUS conditions, and have a perfectly intelligible story. The difficulty, I think, is to understand why this sort of event (the neurons firing) should lead to just this sort of experience (the sensation of red). The psychophysical correlation remains inexplicable, and this is the difficulty of dualism rearing its ahead again, in a darker form.