BOOK REVIEW / Quantum leaps: The rediscovery of the mind by John Searle, MIT Press pounds 9.95

FOR MORE than two decades, the Berkeley philosopher John Searle has battled, sometimes single-

handedly, for an intelligent, common-sense refutation of the wilder claims of Artificial Intelligence. He has always done so with wit, clarity and an entertaining pugnacity. Now Searle aims to 'put the final nail in the coffin of the theory that mind is a computer program' with a blistering attack on the crude materialist claims of the AI theorists, and with his own solution to the mind / body problem from the viewpoint of 'biological naturalism'.

Seeing that Newtonian physics tell them the world consists only of particles and forces, the behaviourist, the functionalist and the AI enthusiast try to account for human beings and our psychology in the same way. They are driven to this 'obviously false' position, Searle says, by an understandable fear of the anti-

scientific and 'spiritualist' claims of traditional dualism. In over-reaction, they reduce the mental to a process of computation. They confuse thinking with the simulation of thought.

What is left out of all computer theories of mind is consciousness. Modern philosophers of mind can't see that its subjective properties have any place in Newton's objective natural world. But according to Searle's 'biological naturalism', consciousness is a feature of the brain, and thus subjectivity must have its rightful place as a feature of the biologically natural world. He introduces the idea that it is an 'emergent' property of certain neurobiological processes. That is, it is a radically new property of their complex structure, just as liquidity or solidity are emergent properties of certain molecular groupings. This is both the most promising and the weakest feature of his position.

Searle admits that emergence as he defines it has no new causal properties. In this he displays an ignorance of quantum physics all too characteristic of most mind /

body philosophers. Any emergent quantum system has new causal properties up to a point. Something like a superfluid has them in large degree. Thus Searle makes a strong case for including consciousness within physics, but his own understanding of physics is ultimately too limited to get him where he would like to go.