This paper criticizes the ways in which `power', `interests', and related notions are used in the analysis of social relations. Two broad approaches to power analysis are considered. The first involves `capacity-outcome' conceptions in which power is defined in terms of the capacity of an agent to secure particular outcomes. The second involves more general usages in which power is supposed to be effective not only as regards the outcomes of particular struggles, but also in the determination of the conditions of struggle themselves by the systematic exclusion or suppression of certain interests. I argue that both approaches operate to foreclose serious analysis of the constitution of arenas of struggle and the forces active in them by means of gross oversimplification of the conditions in which struggles take place.