This chapter focuses on the function debate and will culminate in Christopher Boorse's concept of function. It provides a detailed account of Larry Wright's concept of function, Boorse's reasons for rejecting it, and a rejoinder to Boorse's critique. The chapter discusses Boorse's own version of function and the extent to which it is a viable alternative to Wright's account. Since Boorse thinks that his concept of function meets all of the adequacy demands required by Wright, his positive account is worth exploring. Boorse could respond that, in the context of medicine, the thumping of the heart does have a genuine function because it contributes to the goal of healing within the medical system. Wright's concept of function has two strengths: First, it is able to distinguish genuine functions from accidents once it is realized that his etiological account includes natural selection. Second, his account is able to exclude theism as a necessary requirement.