Chapter XVI: Book II: , Chapter 22. On dialectic

1. Dialectic is the discipline elaborated with a view of ascertaining the causes of things. In itself it is the sub-division of philosophy that is called logical, _i.e._, rational, capable of defining, enquiring and expressing precisely. For it teaches in the several kinds of questions how the true and false are separated by discussion.

2. The first philosophers used dialectic in their discourses, but they did not reduce it to the practical form of an art. After them Aristotle systematized the subject-matter of this branch of learning, and called it dialectic, because there is discussion of words (_dictis_) in it; for λεκτὸν means _dictio_. And dialectic follows after the discipline of rhetoric because they have many things in common.

Chapter 23. On the difference between the dialectical and the rhetorical art.

1. Varro, in the nine books of the _Disciplinae_, distinguished dialectic and rhetoric by the following simile: “Dialectic and rhetoric are as in man’s hand the closed fist and the open palm, the former drawing words together, the latter scattering them.”

2. If dialectic is keener in expressing things precisely, rhetoric is more eloquent in persuading to the belief it desires. The former seldom appears in the schools, the latter goes without a break [from the schools] to the law-court. The former gets few students, the latter often whole peoples.

3. Before they come to the explanation of the Isagoge, philosophers are wont to give a definition of philosophy, in order that the things which concern it may be shown more easily.