 In effect, Schaffner is arguing that the biomedical sciences employ a causal, rather than a teleological, concept of function. This is in the spirit of Cummins’s (1975) systemic analysis of function as the causal contribution a structure makes to the overall operation of the system that includes it. Cummins’s concept of function is not a historical or evolutionary concept. According to Cummins, a component of a system may have a function even it was not designed or selected for. Wakefield has tied disease conceptually to an evolutionary concept of function as a naturally selected capacity. It is doubtful if this connection can be found in either science or common sense about disease. Perhaps in some areas of biology functional ascription is indeed teleological. However, most theorists who have attended to biomedical contexts agree with Boorse and Schaffner that the function of an organ or structure can be understood without thinking of it as an adaptation. Lange (2007) explicitly follows the systemic approach to function. He argues that diseases are incapacities that explain symptoms in causal-analytic terms.Medical understanding requires that functional structures can be identified and analyzed in terms of their contribution to the overall maintenance of the organism as a living system. However, it is also clear that the contribution of some systems – especially reproductive ones – have a purpose that is not tied to homeostatic regulation and organisation in this way, which complicates the picture. Theorists who prefer a causal-historical account to a teleogical one argue that explanation in medicine takes a model of the normal realization of a biological process and uses the model to show how abnormalities stem from the failure of normal relations to apply between components of the model. This requires a non-historical function concept, one that is at home in causal-mechanistic, rather than evolutionary, explanation. Proponents of a teleogical account can respond that those systems, even if they admit of mechanistic explanation, only exist in the first place because they have facilitated survival and reproduction, and that the etiological perspective provides an overall conceptual framework. 