The author argues that ecological economics is developing a blind spot: an unwillingness to consider explicitly social and natural power relations. Following a review of the concept of power in neo-classical economics, ecological economics, political science and sociology, an ecocentric conception of power is developed. The author defines power as 'the production of (or the capacity to produce) effects' and examines some of the implications of this re-definition for natural and social relations. He argues that ecological economics must situate itself within a broader theoretical framework that recognizes the historicity of modern social structures and the need for a fundamental restructuring of social power relations to achieve strong sustainability.