 It is equally problematic whether a unified account of the notion of function as such is possible, but this issue has received considerably more philosophical attention. The notion of function is of paramount importance for characterizing artifacts, but the notion is used much more widely. The notion of an artifact’s function seems to refer necessarily to human intentions. Function is also a key concept in biology, however, where no intentionality plays a role, and it is a key concept in cognitive science and the philosophy of mind, where it is crucial in grounding intentionality in non-intentional, structural and physical properties. Up till now there is no accepted general account of function that covers both the intentionality-based notion of artifact function and the non-intentional notion of biological function—not to speak of other areas where the concept plays a role, such as the social sciences. The most comprehensive theory, that has the ambition to account for the biological notion, cognitive notion and the intentional notion, is Ruth Millikan’s 1984; for criticisms and replies, see B. Preston 1998, 2003; Millikan 1999; Vermaas &amp; Houkes 2003; and Houkes &amp; Vermaas 2010. The collection of essays edited by Ariew, Cummins and Perlman (2002) presents a recent introduction to the general topic of defining the notion of function in general, although the emphasis is, as is generally the case in the literature on function, on biological functions.