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Explanatory Styles in Science

David Hull

Making Sense of Life: Explaining Biological Development with Models, Metaphors, and Machines. Evelyn Fox Keller. xii + 388 pp. Harvard University Press, 2002. $29.95.

Evelyn Fox Keller's Making Sense of Life could just as well have been titled Making Sense of Science. By following the course of the science of embryological development from early work by such nonstandard exemplars as St?phane Leduc, D'Arcy Thompson and Alan Turing to the present, Keller attempts to illustrate the multiplicity of explanatory styles in scientific practice. Scientists do not all use the same methods, nor do they agree regarding what should count as, or be the aim of, an explanation in actual scientific practice. Keller urges this conclusion primarily on the basis of the history of developmental biology. But her argument would only be strengthened by expanding her investigations to, for example, quantum physics, solid state physics, organic chemistry, biochemistry, evolutionary biology and molecular biology, which would only increase this variability of methods and epistemological goals.

According to the notion of science that Keller assimilated as a young theoretical physicist in the 1950s and 1960s, pure science?or at least pure physics?is a matter of pure thought, cleansed of any practical interests or implications of intent or directionality on the part of scientists. One might characterize her current view of science as being closer to "postmodernism" than "positivism"?if these two terms had not been so used and abused as to be all but meaningless. In their most caricatured form, positivists claim that reason, argument and evidence are all that matter to scientists making up their minds, whereas postmodernists think that these considerations play no role whatsoever and that what truly shapes scientific belief are such factors as sexism, racism and homophobia.

Much recent work on understanding science has suffered from being associated with an unsophisticated relativistic epistemology. Realists maintain that scientists discover facts; relativists insist that they merely construct them. Keller uses some of the terminology of this literature, but she should not be tarred with the same brush as these more philosophically inclined students of science because she holds neither set of these beliefs; her position is much more sophisticated. My view on this topic is that the contrast between realism and relativism, no matter how it is made, cuts no scientific ice?realists and relativists, although they disagree on whether we are warranted in believing that the world as we understand it is real, tell the same stories with respect to scientific methods, problems and solutions.

Keller's most fundamental observation is that, just possibly, our abilities to understand may be limited. In fact, the claim that our abilities are unlimited is extremely implausible. Of course, we can supplement our abilities with various machines, from electron microscopes to computers, but the claim that the abilities of these devices are unlimited is also implausible. Right now, we are far from reaching the limits of our supplemented abilities in numerous areas of science, but in the future scientists may just have to settle for "good enough." And we may have reached these limits already in our study of embryonic development, according to Keller, who says, "I see nothing counterintuitive in the possibility that there are phenomena in the natural world extending beyond the grasp of human comprehension?if only by virtue of their sheer complexity."

Scientists in their own research have to assume that they can come to understand the part of the natural world that they have chosen to study, or else they would have no reason to conduct their research. Of course, they may be mistaken?they may have selected one of those areas of the natural world that are too complex to understand scientifically.

Anyone who does not know quite a bit of developmental biology will find Making Sense of Life a hard read, as the book is packed with it. Some of it is out of date, of course, since Keller's approach is historical, and some is bizarre?for example, who would have expected Alan Turing to have set out a model of embryogenesis? But much of the science with which she deals is state-of-the-art embryology.

The fact that developmental biology has played such a minor role in formulations of evolutionary theory from the Modern Synthesis to the present has for some time been considered a scandal. In the past dozen years or so, a new school has arisen, led by Susan Oyama, Paul Griffiths and Russell Gray, which is working to rectify this omission. A reasonable interpretation is that the goal of these scholars is to incorporate our increased knowledge of development into traditional evolutionary theory. But perhaps their ambition is to replace traditional Darwinian versions of evolutionary theory. Keller has set out a compendium of what developmental biologists are currently telling us about embryological development. If she is right about the inherent complexity of these processes, any incorporation of this new knowledge into evolutionary theory will make it even more complicated.-David L. Hull, Philosophy, Northwestern University

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