A Structural Approach to Defining Units of Selection

Abstract

The conflation of two fundamentally distinct issues has generated serious confusion in the philosophical and biological literature concerning the units of selection. The question of how a unit of selection of defined, theoretically, is rarely distinguished from the question of how to determine the empirical accuracy of claims—either specific or general—concerning which unit(s) is undergoing selection processes. In this paper, I begin by refining a definition of the unit of selection, first presented in the philosophical literature by William Wimsatt, which is grounded in the structure of natural selection models. I then explore the implications of this structural definition for empirical evaluation of claims about units of selection. I consider criticisms of this view presented by Elliott Sober—criticisms taken by some (for example, Mayo and Gilinsky 1987) to provide definitive damage to the structuralist account. I shall show that Sober has misinterpreted the structuralist views; he knocks down a straw man in order to motivate his own causal account. Furthermore, I shall argue, Sober's causal account is dependent on the structuralist account that he rejects. I conclude by indicating how the refined structural definition can clarify which sorts of empirical evidence could be brought to bear on a controversial case involving units of selection.