Book 9
3
The same principle holds in all other cases too, so that the formula and knowledge of the actual must precede the knowledge of the potential.
3
In time it is prior in this sense: the actual is prior to the potential with which it is formally identical, but not to that with which it is identical numerically.
4
What I mean is this: that the matter and the seed and the thing which is capable of seeing, which are potentially a man and corn and seeing, but are not yet so actually, are prior in time to the individual man and corn and seeing subject which already exist in actuality.
5
But prior in time to these potential entities are other actual entities from which the former are generated; for the actually existent is always generated from the potentially existent by something which is actually existent—e.g., man by man, cultured by cultured—there is always some prime mover; and that which initiates motion exists already in actuality.
5
We have saidAristot. Met. 7.7, 8. in our discussion of substance that everything which is generated is generated from something and by something; and by something formally identical with itself.
6
Hence it seems impossible that a man can be a builder if he has never built, or a harpist if he has never played a harp; because he who learns to play the harp learns by playing it, and similarly in all other cases.
