Function and Design Revisited

Several analyses of biological function — for example, those of Williams, Millikan, and Kitcher — identify an item's function with what natural selection designed it to do. Allen and Bekoff have disagreed, claiming that natural design is a special case of biological function. I argue that Allen and Bekoff's account of natural design is unduly restrictive and that it fails to mark a principled distinction between function and design. I distinguish two approaches to the phenomenon of natural design — the "trait-centered" approach of Allen and Bekoff and the "organism-centered" approach — and defend the latter. When design is understood according to the organism-centered approach, biological function and design are co-instantiated phenomena.