Graham Cairns-Smith is a chemist whose interests range far more widely than chemistry. He is already known as the proponent of an original theory about how life may have originated, on the basis of clay minerals. His new book tackles an equally ambitious subject: the nature of consciousness.
He starts from the position that consciousness has evolved and that it depends for its existence on an organization of molecules. And he therefore begins the book at a very basic level, with the nature of matter; from there he moves on to the structure and function of nerve cells before coming to the mind and brain. Fundamental questions about the nature of reality are always lurking in the background of the discussion, and there is a good deal about the mysterious paradoxes of quantum theory.
It is fashionable these days to distinguish what has been called the "hard" question about consciousness from other, supposedly easier, questions. The "easy" questions are about such matters as how visual information is processed in the brain or how memory works. These are actually very difficult questions but neuroscientists can at least see possible ways in which they might be approached. In the case of vision, at least, a good deal of progress has been made. The hard question, in contrast, is concerned with what the philosophers call qualia. How is it that the processes occurring in the brain give rise to the subjective world we experience? How, in other words, can we explain the existence of sensations of colour, heat, cold, fear and so on? Thomas Nagel posed the now classic conundrum: what is it like to be a bat? To put it briefly, the easy questions are about the content of consciousness, the hard question is about the existence of consciousness itself.
The hard question is hard because it doesn't seem to arise just from lack of knowledge. It isn't simply a matter of increasing our understanding of how the brain works. The difficulty is rather that we don't seem able to say what sort of explanation is needed to solve the problem. There doesn't appear to be any way to get hold of consciousness in a scientific way; it is absolutely fundamental to our lives and yet, when we try to grasp it, it slips away.
Not everyone, it has to be said, admits the existence of a hard problem. Some writers simply deny that there is anything to be solved at all. They say that brain function and inner experience are really the same thing, and that it is an error on our part to think they are different. They are, however, in a minority, although only a few today are willing to go to the opposite extreme and to speculate that consciousness may be altogether non-physical. Cairns-Smith is not one of these, but neither does he deny the existence of the puzzle. And he doesn't claim to have solved it, although he does point in the directions in which a solution may eventually be found; unlike some writers on this difficult subject, he doesn't give up and say that it is intrinsically too difficult for the human mind to come to terms with.
So what are the features which, he thinks, a successful theory will one day incorporate? First, consciousness is a physical effect, although not necessarily one that is understandable in terms of present-day science. Second, consciousness is something that evolves; rudimentary forms of it exist at numerous levels in the evolutionary tree. But third, specialized structures will have evolved to sustain consciousness; it's not just a by-product of more and more neurons. Finally, there are some events in consciousness that are not wholly determined by changes in the brain; that is, consciousness is simultaneously dependent and independent of its substrate. "Some modulations of consciousness are self-generated."
This is not an easy book. But there are two ways in which a book can be difficult: it can be difficult because the writer expresses himself or herself obscurely, or because the ideas in it are intrinsically hard to grasp. The first kind of difficulty is "bad", the second "good". This book is difficult in the right way; it is delightfully written and is definitely a rewarding read.