 Yet another view is suggested by recent work by Helen Steward emphasizing the traditional idea of a ‘two-way power’ (Steward 2012, Steward 2020; see also Alvarez 2013). Steward argues that actions are exercises of two-way powers — ‘powers which an agent can exercise or not at a given moment, even holding all prior conditions at that moment fixed’ (Steward 2020, 345). These are to be contrasted with one-way powers, which manifest whenever their manifestation conditions are realized, as a fragile glass breaks whenever it is struck. Unlike both the new dispositionalists on the one hand and Vetter on the other, Steward sees a fundamental asymmetry between agents, who are bearers of two-way powers, and mere objects, who are are bearers only of one-way powers. It is natural then to think that what it is to have an ability is to have a two-way power of a certain kind, and that a theory of ability should follow from an account of agency and the two-way powers.