Abstract

Evolutionary theory is thoroughly probabilistic, due to such elements as random mutation, random drift, and stochastic models of speciation and extinction. This uncontroversial claim raises a number of contentious issues: Is evolutionary theory probabilistic in any general sense, or only in a variety of particular, distinct senses? Are these processes inherently probabilistic, or does the use of probabilities simply provide a convenient way to camouflage a multitude of unknown causes? Does chance play an explanatory role in evolutionary theory, and if so, how? My research explores the seemingly disparate meanings of biologists' various usages of the concept of chance in order to shed light on the answers to these questions. ;Recently, philosophers of science have looked to quantum mechanics to settle issues concerning the nature of chance. However, evolutionary theory itself has a decidedly probabilistic character, apart from quantum mechanics; evolutionary theory was given a probabilistic formulation prior to and independently of the development of quantum mechanics. Previous accounts of chance in evolutionary theory have focused primarily on one particular aspect of chance. I examine three distinct areas where chance enters into evolutionary theory in order to provide a comprehensive, synthetic account. Random drift has been the subject of much discussion by philosophers of biology, most notably by Beatty, Brandon, Hodge, Rosenberg, Shanahan, and Sober. My dissertation thus focuses on random drift in order to settle a number of unresolved controversies raised by these philosophers. The discussion of random drift provides a template for exploring random mutation and stochastic models of macroevolution. On the basis of these analyses, I argue that evolutionary theory provides reasons to rethink some of our traditional philosophical ideas about chance