Full Idea
The possession of a potentiality just is the possession of a potentiality to act, and such a potentiality is not unconditional but depends on the obtaining of propitious circumstances, which includes the satisfaction of a ceteris paribus condition.
Gist of Idea
Potentialities are always for action, but are conditional on circumstances
Source
Aristotle (Metaphysics [c.324 BCE], 1048a18)
Book Reference
Aristotle: 'Metaphysics', ed/tr. Lawson-Tancred,Hugh [Penguin 1998], p.264
A Reaction
This seems to be pretty exactly what we mean by a 'power', as something which requires no other driving force, but which only expresses itself with the endless complexity of the rest of nature.