Book I, Chapter 15

Socrates, then, was a hearer of Archelaus, the natural philosopher; and he, reverencing the rule, “Know thyself,” and having assembled a large school, had Plato (there), who was far superior to all his pupils. (Socrates) himself left no writings after him. Plato, however, taking notes of all his (lectures on) wisdom, established a school, combining together natural, ethical, (and) logical (philosophy). But the points Plato determined are these following.