An evolutionary approach faces problems in specifying what the overall evolved function of a system might be and showing how functions contribute to it. First, it is very difficult to assess the relevant evidence that a given biological systems is — as in Wakefield’s treatment — the product of natural selection (Davies 2001, Chapter 5). Since many ailments do not prevent one from living and having children, it is even harder to show that a disease is necessarily the product of a malfunction that