Modern biology, both in its acceptance of the theory of natural selection as the motor of evolution, and in its strong tendency towards ontological reductionism, is materialist in its metaphysics. Organisms, it is assumed, are complex biochemical machines and nothing more; and it is commonly believed that the biochemistry will turn out to be nothing over and above the absolutely fundamental physical particles (the quarks or whatever) in certain complex relations. Life at its evolutionary beginning was but peculiar chemistry and it is difficult to see, on that assumption, how modern evolved life can be anything other than more complicated peculiar chemistry. Humans appear in this story, but only towards the end, in a short footnote, recording a brief redistribution of the fundamental particles and forces.
But a theory must, if it is intellectually viable, account for all the relevant facts. And, as we have seen, when embryonic modern materialism emerged during the Renaissance there were, even then, certain facts concerning the existence of secondary qualities and the existence of consciousness that did not sit easily with it. It has once more become fashionable—particularly among some feminists, I notice—to sneer at the attempts of Descartes and other thinkers to resolve this intellectual tension by resort to dualism, whereby consciousness and the physically lame secondary qualities are tucked away in a non-material mind. But this view at least recognised the problem and, as A.C. Crombie (1964) has argued, was, for its time, scientifically progressive. As it were, it got consciousness and the secondary qualities out of the way while scientists were investigating the physical structure of the world, including the living things it contained. In this respect we might notice that, in supposing the interface between brain and mind to occur in the pineal gland,