ments in a few. For to convert, is when we have changed the conclusion with the remaining interrogations, to subvert one of the data, since it is necessary, if the conclusion is not, that some one of the propositions should be subverted, as when all these are laid down, the conclusion would of necessity be. We must also consider the argument as to every thesis, both that it is so, and that it is not so, and having discovered (this), the solution must be forthwith investigated, for it will happen thus, that at the same time, we shall be exercised both in question, and answer. If also we have nobody else, (we must dispute) to ourselves; also selecting arguments about the same thesis, we must compare them side by side; for this produces a great abundance, for the purpose of constraining conviction, and affords great aid to confutation, when a person is well supplied with arguments both pro and con; since, thus, it happens that care is taken against contraries. Neither is it a small instrument to knowledge and philosophical wisdom, to be able to perceive and to have perceived the results of each hypothesis, for it remains rightly to select one of these. Now there is need for a thing of this kind of a naturally good disposition, and a good disposition is in reality, thus to be able to select properly the true, and to avoid the false; which those naturally (good) are able to perform well, since they who properly love, and hate what is adduced, judge well, what is best.
It is likewise requisite to know well, the arguments about the problems, which generally occur, and especially concerning first theses, since in
