 Wakefield’s approach is not that of a thoroughgoing evolutionary theorist of disease in that sense. Rather, he plugs an etiological account of function into a Boorsian model, and his approach has been developed with little attempt to argue that medicine does in fact use an evolutionary, teleological account of function. In opposition, Schaffner (1993) has argued that although medicine might use teleological talk in its attempts to develop a mechanistic picture of how humans work, the teleology is just heuristic. It can be completely dispensed with when the mechanistic explanation of a given organ or process is complete. Schaffner argues that as we learn more about the causal role a structure plays in the overall functioning of the organism, the need for teleological talk of any kind drops out and is superseded by the vocabulary of mechanistic explanation, and that evolutionary functional ascriptions are merely heuristic; they focus our attention on “entities that satisfy the secondary [i.e. mechanistic] sense of function and that it is important for us to know more about” (1993, 390).