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. (shrink)

Aristotle offers apparently inconsistent explanations for paronymous expressions derived from matter: on the received picture, derived from Metaphysics Θ.7, such expressions are used in all and only cases of substantial change, because predicating the matter directly of a substance would be false; on the error picture, derived from Metaphysics Z.7, the same expressions are used in all and only cases of change from an unclear and nameless privation, because ordinary language users conflate such privations with matter. I propose a resolution: (...) the received picture explains why the usage is fitting, but the error picture explains how the usage originated. (shrink)