Book 12
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Thus it is evident from the foregoing account that there is some substance which is eternal and immovable and separate from sensible things; and it has also been shown that this substance can have no magnitude, but is impartible and indivisible (for it causes motion for infinite time, and nothing finite has an infinite potentialityCf.Aristot. Physics 266a24-b6.; and therefore since every magnitude is either finite or infinite, it cannot have finite magnitude,
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and it cannot have infinite magnitude because there is no such thing at all); and moreover that it is impassive and unalterable; for all the other kinds of motion are posterior to spatial motion. Thus it is clear why this substance has these attributes.
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We must not disregard the question whether we should hold that there is one substance of this kind or more than one, and if more than one, how many; we must review the pronouncements of other thinkers and show that with regard to the number of the substances they have said nothing that can be clearly stated.
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The theory of the Ideas contains no peculiar treatment of the question; for the exponents of the theory call the Ideas numbers, and speak of the numbers now as though they were unlimited and now as though they were limited by the number 10Cf. Aristot. Met. 13.8.17, 20. This was a Pythagorean survival, cf. Vol. I. Introduction. xvi.; but as for why there should be just so many numbers, there is no explanation given with demonstrative accuracy.
