What the functions of consciousness are depends on what one thinks consciousness is.

The word 'consciousness' is often used as if it is a single thing, and as if everyone knows, in a general sense, what that thing is. The very notion of a theory of consciousness implies that someday this thing will be accounted for. But suppose that multiple kinds of consciousness exist. If so, an adequate theory of consciousness would have to be multifaceted rather than unitary. And, accordingly, an account of the function or functions of consciousness would depend on the kind or kinds of consciousness one is referring to. Herein, I use a tripartite taxonomy of human consciousness and explore the relation of each kind to its underlying pre-conscious cognitive processes and their neural underpinnings. I also consider how each kind of consciousness may have evolved, and what the adaptive functions of each may have been.This article is part of the theme issue 'Evolutionary functions of consciousness'.