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Making Sense of Life by Evelyn Fox Keller, Harvard University Press, $29.95/拢19.95, ISBN 0674007468

THIS is a book that asks really big questions. What constitutes a scientific explanation? What do we mean when we say we 鈥渦nderstand鈥� a natural process?

Evelyn Fox Keller has the credentials to put such questions. A towering figure in the philosophy of science, a recipient of a coveted MacArthur Fellowship and a tireless champion of women in science, she had a successful career as a mathematician and physicist before moving into biology. She has experienced at first hand the shock of finding that explanations of a kind that hold good in mathematics were dismissed by biologists as having little force or interest for them. Hence the agenda of this new, deliberately personal and partial exploration, which Keller describes in her preface as a 鈥渕editation鈥�.

In biology, argues Keller, it is descriptions of process that count, rather than the general laws and mathematical equations that govern understanding in the physical sciences. Such descriptions are compelling if they conform to 鈥� or at least do not diverge too dramatically from 鈥� those the community recognises in other areas of their lives. So in the words of that first philosopher of science, Francis Bacon, a description is 鈥渄eeply immersed in matter鈥�, shaped to pre-existing conventions of speech and thought. The explanations that satisfy our need for understanding, the 鈥渟tories we like to hear鈥�, are those that meet our expectations, those drawn from a 鈥渞eservoir of experiences that are not only technical and scientific but also social and political鈥�.

Making Sense of Life is about the importance of recognising this tight connection between the use of language in the social domain and how it produces biological 鈥渦nderstanding鈥�. We can only 鈥渒now鈥� to the extent that our knowledge derives from metaphors and models honed in other, non-scientific contexts. For example, taken on their own, genes have no special explanatory force. Their attractiveness for biological explanation depends, argues Keller, on the ease with which cybernetic metaphors of 鈥渘etworks鈥�, 鈥渇eedback鈥� and 鈥渃ontrol systems鈥� give force to descriptions of biological development cast in genetic terms.

Keller raises a further fundamental question about the nature of explanation in the biological sciences. Why, in the end, do we expect to be able to reduce the complexity of life to something the human mind can fathom? By what mandate is the natural world obliged to make sense to us at all? We have been seduced, she says, by the mathematical simplicity of Newton鈥檚 laws of motion, the elegance with which we can 鈥渨rap our minds around them鈥�. We have come to think of Newton鈥檚 laws as giving us cognitive mastery, because we can manipulate and extend them using nothing more than our mental apparatus. Recent attempts at mathematical modelling of biological processes, by contrast, are computationally complex and resist generalisation.

From now on, according to Keller, scientific explanations will be as many, as partial and as varied as those who seek them. This multiplicity may be the best strategy for understanding biological systems that ultimately remain beyond the reach of the human mind. Embryonic development, for instance, is the outcome of a process of evolution that may not have chosen the simplest or the most elegant path.

There will be some, of course, who are not nearly as comfortable as Keller is with a version of scientific explanation that abandons the quest for mathematical laws and unified theories, and settles instead for connection, wonder, or simply narrative closure. But the central arguments of Making Sense of Life are made with grace and authority. Those who are unsettled by them, and who wish to take issue with Keller, could not ask for a more accomplished and eloquent adversary.