Power is often taken to be a central concept in social and political thought that can contribute to the explanation of many different social phenomena. This article argues that in order to play this role, a general theory of power is required to identify a stable causal capacity, one that does not depend on idiosyncratic social conditions and can thus exert its characteristic influence in a wide range of cases. It considers three promising strategies for such a theory, which ground (...) power in (1) the ability to use force, (2) access to resources, or (3) collective acceptance. It shows that these strategies fail to identify a stable causal capacity. The lack of an adequate general theory of power suggests that the concept lacks the necessary unity to play the broad explanatory role it is often accorded. (shrink)