Book 13
5
Common to all these Platonic theories is the same problem which presents itself in the case of species of a genus when we posit universals—viz. whether it is the Ideal animal that is present in the particular animal, or some other animal distinct from the Ideal animal. This question will cause no difficulty if the universal is not separable; but if, as the Platonists say, Unity and the numbers exist separately, then it is not easy to solve (if we should apply the phrase not easy to what is impossible).
6
For when we think of the one in 2, or in number generally, are we thinking of an Idea or of something else?
6
These thinkers, then, generate geometrical magnitudes from this sort of material principle, but othersThe reference is probably to Speusippus; Plato and Xenocrates did not believe in points (Aristot. Met. 1.9.25, Aristot. Met. 13.5.10 n). generate them from the point (they regard the point not as a unity but as similar to Unity) and another material principle which is not plurality but is similar to it; yet in the case of these principles none the less we get the same difficulties.
