BOOK REVIEW / Reason not the breed: The Nature of Knowledge: Concerning Adaptations, Instinct and the Evolution of Intelligence by Henry Plotkin: Allen Lane/Penguin Press, pounds 20

FOR more than 2,000 years, the theory of knowledge has been the exclusive preserve of philosophy. From Plato to Wittgenstein, philosophers have struggled alone to explain how we can be certain of the future, or the past, or indeed of anything at all. But over the last couple of decades this monopoly has been coming under increasing threat from biologists. Many specialists in human evolution now feel that 'evolutionary epistemology' can solve many of the problems that have stumped philosophers for generations.

It would not necessarily demean philosophy if the biologists were to steal their subject away. The biggest advances in philosophy arguably occur when its topics acquire sufficient maturity to set up as sciences in their own right. Once upon a time, even physics was a part of philosophy. And it is only relatively recently that the lessons learned from philosophy have enabled linguistics, psychology and economics to leave home and start life on their own.

It is a moot point, however, whether evolutionary epistemology is quite ready to capture the theory of knowledge from philosophy. There is no doubt that many facets of the human mind can be illuminated by the biological perspective. Whatever else, humans are products of evolution, and many of our intellectual quirks and curiosities cannot be understood apart from our biological heritage. But the real philosophical puzzles about knowledge, the underlying questions of justification and certainty, remain even after we have taken note of everything biology has to teach us.

Henry Plotkin, Professor of Psychobiology at University College London, aims to introduce evolutionary epistemology to a general readership, and his book displays both the strengths and weaknesses of the biological approach. He has interesting things to say about the way evolution has shaped intellectual life, but when he moves into philosophical territory he tends to lose his way. The first of Plotkin's two main themes is 'Universal Darwinism', by which he means that the trial-and-error structure of Darwinian selection is a pattern reiterated throughout nature. Darwin used this structure to explain the genetic development of species. But Plotkin observes that similar mechanisms govern the multiplication of antibodies in our immune system, the acquisition of new behaviour patterns by individual animals, and the acceptance of new theories by the scientific community. While none of these ideas is exactly new, they are certainly worth repeating, and Plotkin is able to add a few insights of his own.

His other theme is that all biological adaptations are items of knowledge, including such non-mental adaptations as a bird's feathers or a moth's camouflage. His difficulties multiply, however, when he tries to show how this conception of knowledge is helpful to philosophy. As Plotkin is aware, the philosophical quest for knowledge seeks representations of reality which are true and justified. However, it is only in an extremely attenuated sense that a bird's feathers or a moth's colouring constitute a representation of reality. And even if they are representations, they presumably aren't always true, since birds sometimes fail to fly, and moths sometimes become visible to predators.

The trouble with Plotkin, as with most 'evolutionary epistemologists', is that he is working at the wrong level. Biology and allied sciences can explain the basic structure of our intellectual abilities. But most human knowledge flows from a highly self-reflective application of those abilities. When historians reconstruct the past, or mathematicians develop new theorems, they are using their brains in ways that has little to do with biology and much more to do with their self-conscious pursuit of intellectual goals. To understand human knowledge we need to focus on the feasibility of these goals, and not just on the basic abilities which enable us to pursue them.

Inside Plotkin's book there is a better one trying to get out. His own research has investigated the conditions under which intelligent behaviour has an evolutionary advantage over pre-programmed instincts. When he turns to this subject, his book comes alive: it is a pity he devotes only one chapter to it. There is probably a moral here. The best writers of popular biology, from Stephen Jay Gould to Richard Dawkins, are animated by the desire to persuade readers of their pet theories. Perhaps Plotkin would have been better advised to stick to the topics he knows best, and leave the more traditional questions to the philosophers.