We must now draw our conclusions from what has been said, and after summing up the result, bring our inquiry to a close. We have said Footnote 1Cf. Aristot. Met. 7.1. that the objects of our inquiry are the causes and principles and elements of substances. Now some substances are agreed upon by all; but about others certain thinkers have stated individual theories.
Those about which there is agreement are natural substances: e.g. fire, earth, water, air and all the other simple bodies; next, plants and their parts, and animals and the parts of animals; and finally the sensible universe and its parts; and certain thinkers individually include as substances the Forms and the objects of mathematics. Footnote 2Cf. Aristot. Met. 7.2.
And arguments show that there are yet other substances: the essence and the substrate. Footnote 3Cf. Aristot. Met. 7.3-4. Again, from another point of view, the genus is more nearly substance than the species, and the universal than the particulars Footnote 4Cf. Aristot. Met. 7.13. ; and there is a close connection between the universal and genus and the Ideas, for they are thought to be substance on the same grounds. Footnote 5Cf. Aristot. Met. 7.14.
And since the essence is substance, and definition is the formula of the essence, we have therefore systematically examined definition and essential predication. Footnote 6Cf. Aristot. Met. 7.4-6, 12, 15. And since the definition is a formula, and the formula has parts, we have been compelled to investigate parts,
and to discover what things are parts of the substance, and what are not; and whether the parts of the substance are also parts of the definition. Footnote 7Cf. Aristot. Met. 7.10, 11. Further, then, neither the universal nor the genus is substance. Footnote 8Cf. Aristot. Met. 7.13, 16.
As for the Ideas and the objects of mathematics (for some say that these exist apart from sensible substances) we must consider them later. Footnote 9Books 13 and 14. But now let us proceed to discuss those substances which are generally accepted as such.
Now these are the sensible substances, and all sensible substances contain matter.
And the substrate is substance; in one sense matter (by matter I mean that which is not actually, but is potentially, an individual thing); and in another the formula and the specific shape (which is an individual thing and is theoretically separable); and thirdly there is the combination of the two, which alone admits of generation and destruction, Footnote 10Cf. Aristot. Met. 7.8. and is separable in an unqualified sense—for of substances in the sense of formula some are separable Footnote 11In point of fact the only form which is absolutely separable is Mind or Reason. Cf. Aristot. Met. 12.7, 9. and some are not.
That matter is also substance is evident; for in all opposite processes of change there is something that underlies those processes; e.g., if the change is of place , that which is now in one place and subsequently in another; and if the change is of magnitude , that which is now of such-and-such a size, and subsequently smaller or greater; and if the change is of quality , that which is now healthy and subsequently diseased.
Similarly, if the change is in respect of being , there is something which is now in course of generation, and subsequently in course of destruction, and which is the underlying substrate, now as this individual thing, and subsequently as deprived of its individuality. In this last process of change the others are involved, but in either one or two Footnote 12i.e., locomotion does not involve substantial change; alteration may or may not involve it (in Aristot. Met. 9.8.17 we find that it does not); increase or decrease does involve it. of the others it is not involved; for it does not necessarily follow that if a thing contains matter that admits of change of place, it also contains matter that is generable and destructible. Footnote 13e.g., the heavenly bodies, though imperishable, can move in space (Aristot. Met. 8.4.7, Aristot. Met. 12.2.4). The difference between absolute and qualified generation has been explained in the Physics. Footnote 14Aristot. Phys. 225a 12-20; cf. Aristot. De Gen. et Corr. 317a 17-31.