Abstract
In Metaphysics Θ 1, Aristotle claims that the active power is definitionally prior to the passive power. Commentators have been puzzled by this claim, because the definitions appear, and seemingly should be, symmetric. However, their attempts to address this difficulty are dissatisfying, for commentators have not adequately appreciated what the difficulty is: they show (at most) how every kind of active power can be definitionally prior to every kind of passive power, but do not address how the active power as such can be definitionally prior to the passive power as such. We undertake three tasks. First, we clarify the puzzle, demonstrating that it is the claim that the active power as such is definitionally prior to the passive power as such that stands in need of justification. Second, we defend a reading of the definitions which dissolves the appearance of symmetry. Third, we explain why the view that the active power is prior to the passive is philosophically attractive.