XIII. These then are the books which were written by him. And in them he expresses the following opinions:—that there is in philosophy a two-fold division; one practical, and the other theoretical. Again, the practical is divided into ethical and political, under which last head are comprised considerations affecting not only the state, but also the management, of a single house. The theoretical part, too, is subdivided into physics and logic; the latter forming not a single division, turning on one special point, but being rather an instrument for every art brought to a high degree of accuracy. And he has laid down two separate objects as what it is conversant about, the persuasive and the true. And he has used two means with reference to each end; dialectics and rhetoric, with reference to persuasion; analytical examination and philosophy, with reference to truth; omitting nothing which can bear upon discovery, or judgment, or use. Accordingly, with reference to discovery, he has furnished us with topics and works on method, which form a complete armoury of propositions, from which it is easy to provide one’s self with an abundance of probable arguments for every kind of question. And with reference to judgment, he has given us the former and posterior analytics; and by means of the former analytics, we may arrive at a critical examination of principles; by means of the posterior, we may examine the conclusions which are deduced from them. With reference to the use or application of his rules, he has given us works on discussion, on question, on disputation, on sophistical refutation, on syllogism, and on things of that sort.