XI. Now, of Philosophers some were dogmatic, and others were inclined to suspend their opinions. By dogmatic, I mean those who explain their opinions about matters, as if they could be comprehended. By those who suspend their opinions, I mean those who give no positive judgment, thinking that these things cannot be comprehended. And the former class have left many memorials of themselves; but the others have never written a line; as for instance, according to some people, Socrates, and Stilpo, and Philippus, and Menedemus, and Pyrrho, and Theodorus, and Carneades, and Bryson; and, as some people say, Pythagoras, and Aristo of Chios, except that he wrote a few letters. There are some men too who have written one work only, Melissus, Parmenides, and Anaxagoras; but Zeno wrote many works, Xenophanes still more; Democritus more, Aristotle more, Epicurus more, and Chrysippus more.
XII. Again, of philosophers some derived a surname from cities, as, the Elians, and Megaric sect, the Eretrians, and the Cyrenaics. Some from the places which they frequented, as the Academics and Stoics. Some from accidental circumstances, as the Peripatetics; or, from jests, as the Cynics. Some again from their dispositions, as the Eudæmonics; some from an opinion, as the Elenctic, and Analogical schools. Some from their masters, as the Socratic and Epicurean philosophers; and so on. The Natural Philosophers were so called from their study of nature; the Ethical philosophers from their investigation of questions of morals (περὶ τὰ ἔθη). The Dialecticians are they who devote themselves to quibbling on words.
XIII. Now there are three divisions of philosophy. Natural, Ethical, and Dialectic. Natural philosophy occupies itself about the world and the things in it; Ethical philosophy about life, and the things which concern us; Dialectics are conversant with the arguments by which both the others are supported.
Natural philosophy prevailed till the time of Archelaus; but after the time of Socrates, Ethical philosophy was predominant; and after the time of Zeno the Eleatic, Dialectic philosophy got the upper hand.
Ethical philosophy was subdivided into ten sects; the Academic, the Cyrenaic, the Elian, the Megaric, the Cynic, the Eretrian, the Dialectic, the Peripatetic, the Stoic, and the Epicurean. Of the old Academic school Plato was the president; of the middle, Arcesilaus; and of the New, Lacydes:—the Cyrenaic school was founded by Aristippus the Cyrenian; the Elian, by Phædo, of Elis; the Megaric, by Euclid, of Megara; the Cynic, by Antisthenes, the Athenian; the Eretrian, by Menedemus, of Eretria; the Dialectic by Clitomachus, the Carthaginian; the Peripatetic, by Aristotle, the Stagirite; the Stoic, by Zeno, the Cittiæan; the Epicurean school derives its name from Epicurus, its founder.