Full Idea
Powers explain behaviours regardless of whether they are necessary for membership in a particular class of things.
Gist of Idea
Powers give explanations, without being necessary for some class membership
Source
Anjan Chakravarrty (Inessential Aristotle: Powers without Essences [2012], 3)
A Reaction
This seems right, and is important for driving a wedge between powers and essences. If there are essences, they are not simply some bunch of powers.