(Fourth)

It may be said: Grant that this is so. These disciplines are purely rational: they do not rest on following anyone’s authority, but are known through reason alone. They therefore cannot be validated by transmitted reports; indeed, they must be discussed solely on rational grounds. When clear reason demonstrates the falsity of their erroneous elements, its judgment cannot be rejected. Their adherents have not claimed that these disciplines derive from any source that must be believed, but rather from pure reason. They must therefore be judged according to what clear reason requires.

Section

They have argued, as mentioned, that induction is inferior to syllogistic reasoning—specifically, subsumptive syllogism—and that reasoning by analogy is inferior to induction. They say:

“Reasoning by analogy yields only probability, and the subject of its judgment may be a particular. Induction, by contrast, may yield certainty, and the subject of its judgment can only be a universal.”

They say:

“This is because induction consists in judging a universal on the basis of what has been established in its particular instances. If this has been established in all its instances, the induction is complete. An example is judging that everything that moves is corporeal, since corporeality is predicated of all the particular instances of moving things: inanimate objects, animals, and plants. Incomplete induction is exemplified by judging that an animal, when eating, moves its lower jaw as it chews, because this is found in most instances. Yet the opposite may be true of those instances that have not been examined