I defend the historical definition of "function" originally given in my Language, Thought and Other Biological Categories (1984a). The definition was not offered in the spirit of conceptual analysis but is more akin to a theoretical definition of "function". A major theme is that nonhistorical analyses of "function" fail to deal adequately with items that are not capable of performing their functions.

We examine two approaches to functions: etiological and forward-looking. In the context of functions, we raise the question, familiar to philosophers of mind, about the explanatory role of properties that are not supervenient on the mere dispositional features of a system. We first argue that the question has no easy answer in either of the two approaches. We then draw a parallel between functions and goal directedness. We conclude by proposing an answer to the question: The explanatory importance of nonsupervenient (...) properties (like having the function of doing something, or like being goal-directed) does not lie in any special causal mechanism through which these properties bring about their effects; it lies rather in the different classification of the explananda types that these properties generate. (shrink)