this treatise is useful. It is so for three: exercise, conversation, philosophical science. That it is useful for exercise, appears evident from these, that possessing method, we shall be able more easily to argue upon every proposed subject. But for conversation (it is useful), because having enumerated the opinions of the many, we shall converse with them, not from foreign, but from appropriate dogmas, confuting whatever they appear to us to have erroneously stated. Again, (it is useful) for philosophical science, because being able to dispute on both sides, we shall more easily perceive in each the true and the false; also, (it is applicable) to the first principles of each science, since we cannot say any thing about these from the appropriate principles of a proposed science, as they are the first principles of all, but we must necessarily discuss these through probabilities in the singulars. This however is peculiar, or especially appropriate to dialectic, for being investigative, it possesses the way to the principles of all methods.
Chapter 3
We shall possess this method perfectly when we are similarly disposed, as in rhetoric, medicine, and such like powers; and this is to effect what we choose from possibilities, since neither will the rhetorician persuade from every mode, nor the physician heal, but if a man omits no possibility we say that he sufficiently possesses science.
Chapter 4
First then let us examine of what this method consists. If therefore we assume for how many, what
