Full Idea
Motion is the fulfilment of what exists potentially, in so far as it exists potentially.
Gist of Idea
Motion fulfils potentiality
Source
Aristotle (Physics [c.337 BCE], 201a10-11), quoted by Rowland Stout - Action 6 'Two'
Book Reference
Stout,Rowland: 'Action' [Acumen 2005], p.89
A Reaction
We might put that as 'all motion is the fulfilment of a natural power'. But that gives the source of motion, and not its intrinsic nature.