Abstract

One would think that after one hundred years of earnest work, Darwinians would know what it is that nature selects for. Yet while some Darwinians argue that nature selects only for genes, others insist that the units being selected for are organisms and groups of organisms. Darwinians have also had difficulty identifying the fundamental principles of their theory. Some think the basic principle is the survival of the fittest; others deny that this principle is an important part of their theory. ;Philosophers of biology think that many of these fundamental issues could be resolved if we had a clearer understanding of evolutionary theory. Traditionally philosophers have tried to clarify scientific theories by formulating their central laws as universal statements in a formal language. This approach has been challenged recently by those who argue that theories should be thought of as sets of models, not as sets of universal statements. The central aim of my dissertation is to demonstrate how this shift in focus from statements to models can help resolve several long-standing problems associated with the theory of natural selection. ;In the first chapter, I identify the fundamental principles of Darwin's original theory of natural selection. I do so by ignoring Darwin's generalizations and focusing on the models of natural selection presented in the Origin as imaginary illustrations. I clarify Darwin's analogical argument for natural selection in the second chapter. My analysis is based upon the view that analogical reasoning involves using specific information about one model to infer specific information about isomorphic models. In the third chapter, I argue that the principle of the survival of the fittest is untestable and plays no role in specifying the models of natural selection. The fourth chapter concerns the units of selection controversy. I argue that many selection processes can be accounted for by more than one model and that the choice between them is often a pragmatic one. While the four chapters deal with different problems, they are related by their common perspective on the structure of scientific theories, a perspective which I suggest is largely responsible for their individual successes