Lives and Opinions of Eminent Philosophers

​This method of induction is rhetorical, since rhetoric also conducts its inquiry concerning particulars, not universals; for it inquires not about justice itself, but about particular instances of justice. The other method is dialectical, wherein the universal is demonstrated beforehand through the particulars. For instance, it is inquired whether the soul is immortal, and whether the living come from the dead; and this is demonstrated in the On the Soul through a certain universal proposition, namely that opposites come from opposites. And this universal proposition itself is established from certain existing particulars: for example, that sleeping comes from being awake and vice versa, and the greater from the smaller and vice versa. And he used this method for establishing his own doctrines.

​Just as anciently in tragedy, at first the chorus alone performed the drama, but later Thespis invented a single actor in order to give the chorus a rest, and Aeschylus a second, and Sophocles a third, thereby bringing tragedy to its completion, so also the discourse of philosophy was at first of a single kind, namely physical, but secondarily Socrates added the ethical, and thirdly Plato added the dialectical, thus bringing philosophy to perfection. Thrasyllus says that he even published his dialogues according to tragic tetralogy, just as the poets used to compete with four plays—at the Dionysia, Lenaea, Panathenaea, and Chytroi—of which the fourth was a satyr play; and the four plays were called a tetralogy.

​There are, then, he says, in all fifty-six genuine dialogues of his, the Republic being divided into ten books—which Favorinus in the second book of his Miscellaneous History says is found almost in its entirety in Protagoras' Antilogies—and the Laws into twelve. There are nine tetralogies, with the Republic occupying the place of a single book, and the Laws likewise of one. He places first, then, the tetralogy that has a common subject, for he wishes to show what sort of thing the philosopher's life would be. He also uses double titles for each of the books, one derived from the name and the other from the subject matter.

​Leading this tetralogy, which is the first, is Euthyphro, or On Piety, and the dialogue is peirastic; second, the Apology of Socrates, ethical; third, Crito, or On What is to be Done, ethical; fourth, Phaedo, or On the Soul, ethical. The second tetralogy is headed by Cratylus, or On Correctness of Names, logical; Theaetetus, or On Knowledge, peirastic; Sophist, or On Being, logical; Statesman, or On Kingship, logical. The third is headed by Parmenides, or On Ideas, logical; Philebus, or On Pleasure, ethical; Symposium, or On the Good, ethical; Phaedrus, or On Love, ethical.

​The fourth is headed by Alcibiades, or On the Nature of Man, maieutic; Second Alcibiades, or On Prayer, maieutic; Hipparchus, or The Lover of Gain, ethical; Rival Lovers, or On Philosophy, ethical. The fifth is headed by Theages, or On Philosophy, maieutic; Charmides, or On Temperance, peirastic; Laches, or On Courage, maieutic; Lysis, or On Friendship, maieutic. The sixth is headed by Euthydemus, or The Disputant, anatreptic; Protagoras, or Sophists, endeictic; Gorgias, or On Rhetoric, anatreptic; Meno, or On Virtue, peirastic.

​The seventh is headed by the two Hippias—the First, or On the Beautiful, the Second, or On Falsehood—anatreptic; Ion, or On the Iliad, peirastic; Menexenus, or The Funeral Oration, ethical. The eighth is headed by Clitophon, or Exhortation, ethical; Republic, or On Justice, political; Timaeus, or On Nature, physical; Critias, or Atlanticus, ethical. The ninth is headed by Minos, or On Law, political; Laws, or On Legislation, political; Epinomis, or The Nocturnal Council, or The Philosopher, political; thirteen Epistles, ethical—