Functions and Causal Roles

Abstract

This chapter is about the causal role theory of function. According to this view, roughly, a function of a part of a system consists in its contribution to some system-level effect, which effect has been picked out as especially interesting by a group of researchers. I will discuss Robert Cummins’ original formulation of the view, and then present a more sophisticated variation, the mechanistic causal role theory, due to Carl Craver and Paul Sheldon Davies. I then discuss the classic problem of overbreadth, namely, that it seems to attribute functions too liberally. I distinguish two different versions of this problem: the problem of non-functional traits and the problem of dysfunctional traits. I provide a critical assessment of the ways causal role theorists have tried to solve these problems. Many philosophers of biology today have accepted a pluralistic stance, according to which both the selected effects theory, and the causal role theory, capture important elements of biological usage. I distinguish two forms of pluralism. The first (and most popular), between-discipline pluralism, holds that the selected effects theory mainly captures the way evolutionary biologists use the term “function” and the causal role theory mainly captures the way “function” is used in other disciplines. I object to this division of labor and recommend a new form of pluralism, within-discipline pluralism, which emphasizes the co-existence of function concepts within any given discipline.