Book 12
7
In another sense, however, proximate causes are different; there are as many proximate causes as there are contraries which are predicated neither as genera nor with a variety of meaningsi.e., individual forms and privations of individual things.; and further the particular material causes are different. Thus we have stated what the principles of sensible things are, and how many they are, and in what sense they are the same and in what sense different.
1
Since we have seenAristot. Met. 12.1.3, 4. that there are three kinds of substance, two of which are natural and one immutable, we must now discuss the last named and show that there must be some substance which is eternal and immutable. Substances are the primary reality, and if they are all perishable, everything is perishable. But motion cannot be either generated or destroyed, for it always existedCf. Aristot. Physics 8.1-3; nor can time, because there can be no priority or posteriority if there is no time.The argument seems to be: If we assume that time was generated, it follows that before that there was no time; but the very term before implies time. The same applies to the destruction of time.
2
Hence as time is continuous, so too is motion; for time is either identical with motion or an affection of it.Cf. Aristot. Met. 11.12.1 n. But there is no continuous motion except that which is spatial, of spatial motion only that which is circular.These statements are proved inAristot. Physics 8.8, 9.
