tremes also are: lastly, if there be any thing contrary to genus we most notice whether the contrary also is in the contrary, since if it be, the proposed (species) is evidently in the proposed genus.
Again, in cases and co-ordinates, both the subverter and confirmer (must notice) whether they are similarly consequent, since at the same time they are present, or are not present, with one thing, and with all, as if justice is a certain science, what is justly, is also scientifically, (done), and a just is a scientific man, but if something of these is not, neither is any of the rest.
Chapter 4
Such things also (must be noticed), which are similarly affected with respect to each other, thus the pleasant subsists with reference to pleasure, similarly to the useful with reference to good, for each is effective of the other. If then pleasure is what is good, the pleasant will be what is useful, for it would be clearly effective of good, since pleasure is good. The like also occurs in generations and corruptions, as, if to build is to energize, to have built is to have energized, and if to learn is to remember, to have learned is to have remembered, and if to be dissolved is to be corrupted, to have been dissolved is to have been corrupted, and dissolution is a certain corruption. So also in those which have the power to generate and to corrupt, and in powers and uses, and in short, according to any kind of likeness, as we have observed in generation and corruption, consideration must be paid both by the subverter and the confirmer. For if what is corruptive dissolves, to be corrupted is to be dissolved, and if what is generative is effective, to be generated is to be made, and generation is making, and the same in powers and uses, since if power is disposition, to be able also is to be disposed; and if the use of a thing is energy, to use is to energize, and to have used is to have energized.
