Darwin's causal pluralism

Historians of Biology have divided nineteenth century naturalists into two basic camps, Functionalists and Structuralists. This division is supposed to demarcate the alternative causal presuppositions working beneath research programs. If one is functionally oriented, then organic form will be contingent upon the causal powers of the environment. If structurally oriented, one argues for nonfunctional mechanisms (e.g., internal laws of growth) to account for organic form. Traditionally, Darwin has been grouped with the functionalists because natural selection (an adaptational mechanism) plays the prominent role in shaping organic form. In this paper, I sketch the dichotomy of functionalism versus structuralism and then argue that Darwin cannot be characterized adequately with this dichotomy. I argue that Darwin can incorporate both causal stories because he makes two important modifications to the traditional metaphysical presuppositions. I then offer some brief reflections on the import of Darwin's causal pluralism for the Philosophy of Science.