The multiple action account of filling a role

Functionalism, the doctrine that tokens realize types in virtue of filling a functional role, remains a dominant view in the metaphysics of mind and of science. At the heart of the view is the concept of filling a functional role. Despite this importance, the dominant conception of filling a functional role, the subset approach, has some well-known problems and a comprehensive alternative is needed to replace it. In this paper, I present a novel account of filling a functional role, the multiple action account. On the multiple action account, a token fills the functional role of some type by having a possibly distinct functional role. For some Y that is part of some type’s functional role, a token does Y by doing X, some part of the token’s functional role. I defend the ‘by test’ for determining when a token does Y by doing X. I conclude with an exploration and defense of three important implications of this view: first, that there are essentially functional properties; second, that some token can have a range of causal properties, including some that belong to essentially functional types and some that do not; and third, that there are important modal differences in the various things that a token does.