Biological functions and dysfunctions: a selected dispositions approach

Justin Garson has recently argued that proper functions are proximal activities of traits selected by phylogenetic or ontogenetic selection processes, and that traits are dysfunctional only if they cannot perform their proper functions for constitutional reasons. We partially agree with Garson, but reject the view that functions are proximal activities, as well as his account of dysfunctions. Instead, we propose our own theory that biological functions are selected dispositions and that a trait is dysfunctional in virtue of not having the dispositions for which it was selected. This account can explain both defects (or dysfunctions in Garson’s sense) and dysfunctions due to environmental factors. Moreover, it offers a neat way to explain the graduality of dysfunction.