In this paper I discuss recent debates concerning etiological theories of functions. I defend an etiological theory against two criticisms, namely the ability to account for malfunction, and the problem of structural
doubles
. I then consider the arguments provided by Bigelow and Pargetter (1987) for a more
forward looking
account of functions as propensities or dispositions. I argue that their approach fails to address the explanatory problematic for which etiological theories were developed.
Key words Function - fitness - dispositions - explanation
An early version of this paper was presented at the International Society for History, Philosophy and Social Studies of Biology, in London, Ontario, July 1989. See also Mitchell (1993) for related arguments against Bigelow and Pargetter (1987). I wish to thank the anonymous reviewer for detailed, helpful comments.