"And the reason motion seems to be indefinite is that one cannot place it as a potency of things or as a being-at-work. For neither the potency to be this-much nor the actively being this-much is necessarily a being-moved; so motion seems to be a certain being-at-work, but incomplete. The reason for this is that the potency, of which it is the [complete] being-at-work, is itself something incomplete. On account of this it is difficult to get hold of what it is. For one must place it as a deprivation, or a potency, or an unqualified being-at-work; but none of these seems admissable. There remains, then, the way stated, that it is a certain being-at-work, a being-at-work of such a kind as we have described, difficult to bring into focus, but possible to be."
- Physics, Aristotle
Sigh.. if only philosophers were better writers.