The Lives and Opinions of Eminent Philosophers

by Diogenes Laertius

But we are not unaware that some writers distinguish the various dialogues in a different manner from what we do. For they say that some of them are dramatic, and others narrative, and others of a mixed nature. But they, in this division, are classifying the dialogues in a theatrical rather than in a philosophical manner. Some of the dialogues also refer to subjects of natural philosophy, such as the Timæus. Of the logical class, there are the Politics, the Cratylus, the Parmenides, and the Sophist. Of the ethical kind there is the defence of Socrates, the Crito, the Phædo, the Phædrus, the Banquet, the Menexenus, the Clitophon, the Epistles, the Philebus, the Hipparchus, and the Rival Lovers. Of the political class there is the Republic, the Laws, the Minos, the Epinomis, and the Atlanticus. Of the midwife description we have the two Alcibiades’s, the Theages, the Lysis, the Laches. Of the tentative kind, there is the Euthyphro, the Meno, the Ion, the Charmides, and the Theætetus. Of the demonstrative description, we have the Protagoras, and of the distinctive class the Euthydemus, the two Hippias’s, and the Gorgias. And this is enough to say about the dialogues as to what they are, and what their different kinds are.

XXXIII. But since there is also a great division of opinion respecting them, from some people asserting that in them Plato dogmatizes in a positive manner, while others deny this, we had better also touch upon this part of the question. Now, dogmatizing is laying down dogmas, just as legislating is making laws. But the word dogma is used in two senses; to mean both that which we think, and opinion itself. Now of these, that which we think is the proposition, and opinion is the conception by which we entertain it in our minds. Plato then explains the opinions which he entertains himself, and refutes false ones; and about doubtful matters he suspends his judgment. His opinions of matters as they appear to him he puts into the mouth of four persons, Socrates, Timæus, an Athenian poet, and an Eleatic stranger. But the strangers are not, as some people have supposed, Plato and Parmenides, but certain nameless imaginary characters. Since Plato asserts as undeniable axioms all the opinions which he puts into the mouth of Socrates or Timæus. But when he is refuting false propositions, he introduces such characters as Thrasymachus, and Callicles, and Polus, and Gorgias, and Protagoras, Hippias too, and Euthydemus, and men of that stamp. But when he is demonstrating anything, then he chiefly uses the inductive form of argument, and that too not of one kind only, but of two. For induction is an argument, which by means of some admitted truths establishes naturally other truths which resemble them. But there are two kinds of induction; the one proceeding from contraries, the other from consequents. Now, the one which proceeds from contraries, is one in which from the answer given, whatever that answer may be, the contrary of the principle indicated in the question must follow. As for instance. My father is either a different person from your father, or he is the same person. If now your father is a different person from my father, then as he is a different person from a father, he cannot be a father. If, on the other hand, he is the same person as my father, then, since he is the same person as my father, he must be my father. And again, if man be not an animal, he must be either a stone or a piece of wood; but he is not a stone or a piece of wood, for he is a living animal, and capable of independent motion. Therefore, he is an animal. But, if he is an animal, and a dog or an ox is likewise an animal, then man must be an animal, and a dog, and an ox.—This then is the method of induction in contradiction and contention, which Plato was accustomed to employ, not for the purpose of establishing principles of his own, but with the object of refuting the arguments of others.

Now, the inductive kind of argument drawn from consequents is of a twofold character. The one proving a particular opinion by an admitted fact of an equally particular nature; or else going from particulars to generals. And the first of these two divisions is the oratorical one, the second the dialectic one. As for instance, in the former kind the question is whether this person has committed a murder; the proof is that he was found at the time covered with blood. But this is the oratorical method of employing the induction; since oratory is conversant about particulars, and does not concern itself about generals. For its object is not to ascertain abstract justice, but only particular justice. The other is the dialectic kind, the general proposition having been established by particular ones. As for instance, the question is whether the soul is immortal, and whether the living consist of those who have once been dead; and this proposition Plato establishes in his book on the Soul, by a certain general proposition, that contraries arise out of contraries; and this identical general proposition is established by certain particular ones. As, for instance, that sleep follows on waking, and waking from sleeping, and the greater from the less, and reversely the less from the greater. And this kind of induction he used to employ for the establishment of his own opinions.

XXXIV. Anciently, in tragedy, it was only the chorus who did the whole work of the play; but subsequently, Thespis introduced one actor for the sake of giving the chorus some rest, and Æschylus added a second, and Sophocles a third, and so they made tragedy complete. So in the same manner, philosophical discourse was originally uniform, concerning itself solely about natural philosophy; then Socrates added to it a second character, the ethical: and Plato a third, the dialectic: and so he brought philosophy to perfection.

XXXV. But Thrasybulus says that he published his dialogues as the dramatic poets published their tetralogies. For, they contended with four plays, (and at four festivals, the Dionysiac, the Lenæan, the Panathenæan, and the Chytri), one of which was a satiric drama, and the whole four plays were called a tetralogy. Now, people say, the whole of his genuine dialogues amount to fifty-six; the treatise on the Republic being divided into ten books, (which Phavorinus, in the second book of his Universal History, says may be found almost entire in the Contradictions of Protagoras), and that on Laws into twelve. And there are nine tetralogies, if we consider the Republic as occupying the place of one book, and the Laws of another. He arranges, therefore, the first tetralogy of these dialogues which have a common subject, wishing to show what sort of life that of the philosopher may have been. And he uses two titles for each separate book, taking one from the name of the principal speaker, and the other from the subject.

This tetralogy then, which is the first, is commenced by the Euthyphron, or what is Holy; and that dialogue is a tentative one. The second is the Defence of Socrates, a moral one. The third is the Criton, or What is to be done, a moral one. The fourth is the Phædo, or the Dialogue on the Soul, a moral one.

The second tetralogy is that of which the first piece is the Cratylus, or the correctness of names, a logical one. The Theætetus, or Knowledge, a tentative one. The Sophist, or a dialogue on the Existent, a logical one. The Statesman, or a dialogue of Monarchy, a logical one.

The first dialogue in the third tetralogy is the Parmenides, or a dialogue of Ideas, a logical one. The second is the Philebus, or on Pleasure, a moral one. The Banquet, or on the Good, a moral one. The Phædrus, or on Love, a moral one.

The fourth tetralogy opens with the Alcibiades, or a treatise on the Nature of Man, a midwife-like work. The second Alcibiades, or on Prayer, a piece of the same character. The Hipparchus, or on the Love of Gain, a moral one. The Rival Lovers, or a treatise on Philosophy, a moral one.