Book 3
1.54
And again: If man is not an animal, he will be either a stick or a stone. But he is not a stick or a stone; for he is animate and self-moved. Therefore he is an animal. But if he is an animal, and if a dog or an ox is also an animal, then man by being an animal will be a dog and an ox as well. This is the kind of induction which proceeds by contradiction and dispute, and Plato used it, not for laying down positive doctrines but for refutation. The other kind of induction by agreement appears in two forms, the one proving the particular conclusion under discussion from a particular, the other proceeding by way of the universal [by means of particular facts]. The former is suited to rhetoric, the latter to dialectic. For instance, under the first form the question is raised, Did so-and-so commit a murder? The proof is that he was found at the time with stains of blood on him.
1.55
This is the rhetorical form of induction, since rhetoric also is concerned with particular facts and not with universals. It does not inquire about justice in the abstract, but about particular cases of justice. The other kind, where the general proposition is first established by means of particular facts, is the induction of dialectic. For instance, the question put is whether the soul is immortal, and whether the living come back from the dead. And this is proved in the dialogue On the Soul by means of a certain general proposition, that opposites proceed from opposites. And the general proposition itself is established by means of certain propositions which are particular, as that sleep comes from waking and vice versa, the greater from the less and vice versa. This is the form which he used to establish his own views.
