Book 1
9
Anaxagoras of Clazomenae—prior to Empedocles in point of age, but posterior in his activities—says that the first principles are infinite in number. For he says that as a general rule all things which are, like fire and water,This is Aristotle’s illustration; apparently Anaxagoras did not regard the elements as homoeomerous (i.e. composed of parts which are similar to one another and to the whole). Cf. Aristot. De Caelo 302a 28, Aristot. De Gen. et Corr. 314a 24. homoeomerous, are generated and destroyed in this sense only, by combination and differentiation; otherwise they are neither generated nor destroyed, but persist eternally.Cf. Anaxagoras Fr. 4 (Diels); and see Burnet, E.G.P. 130.
10
From this account it might be supposed that the only cause is of the kind called material. But as men proceeded in this way, the very circumstances of the case led them on and compelled them to seek further; because if it is really true that all generation and destruction is out of some one entity or even more than one, why does this happen, and what is the cause?
11
It is surely not the substrate itself which causes itself to change. I mean, e.g., that neither wood nor bronze is responsible for changing itself; wood does not make a bed, nor bronze a statue, but something else is the cause of the change. Now to investigate this is to investigate the second type of cause: the source of motion, as we should say.
