Lives and Opinions of Eminent Philosophers

​We are well aware that some classify the dialogues differently—for they call some of them dramatic, others narrative, and others mixed—but they have designated the distinction among the dialogues in a manner more tragic than philosophical. Belonging to the physical class is, for example, the Timaeus; to the logical, the Statesman, Cratylus, Parmenides, and Sophist; to the ethical, the Apology, Crito, Phaedo, Phaedrus, Symposium, Menexenus, Clitophon, the Epistles, Philebus, Hipparchus, and Rival Lovers; and to the political, the Republic, Laws, Minos, Epinomis, and Atlanticus.

​Belonging to the maieutic are the two Alcibiades, Theages, Lysis, and Laches; to the peirastic, the Euthyphro, Meno, Ion, Charmides, and Theaetetus; to the endeictic, for example, the Protagoras; and to the anatreptic, the Euthydemus, Gorgias, and the two Hippias. As to what a dialogue is and what its differences are, let it suffice to have said this much.Now, since there is great dissension, and some assert that he dogmatizes while others say he does not, come, let us discuss this matter as well. To dogmatize, then, is to lay down doctrines, just as to legislate is to lay down laws. And doctrine is spoken of in two ways: both that which is opined and the opinion itself.

​Of these, that which is opined is a proposition, while the opinion is a conception. Plato, therefore, declares his view concerning what he has comprehended, refutes what is false, and suspends judgment concerning obscure matters. And concerning his own views, he makes statements through four characters: Socrates, Timaeus, the Athenian Stranger, and the Eleatic Stranger. These Strangers are not, as some have supposed, Plato and Parmenides, but are anonymous fictional creations; for Plato dogmatizes even when speaking the words of Socrates and Timaeus. On the other hand, for what is false, he introduces persons who are refuted, such as Thrasymachus, Callicles, Polus, Gorgias, Protagoras, and further Hippias, Euthydemus, and indeed others like them.

​When making demonstrations, he uses most often the method of induction, not indeed in a single manner, but in two ways. For induction is an argument which, through certain truths, appropriately adduces a truth resembling itself. And there are two methods of induction: that by opposition and that from consequence. The one by opposition, then, is that from which the opposite will follow for the person questioned upon every answer, such as: 'My father is either different from your father or the same. If, then, your father is different from my father, being different from father, he cannot be a father; but if he is the same as my father, being the same as my father, he must be my father.'

​And again: 'If man is not an animal, he must be a stone or a piece of wood. But he is not a stone or a piece of wood, for he is animate and moves of himself; therefore he is an animal. But if he is an animal, and a dog and an ox are also animals, then man, being an animal, would also be a dog and an ox.' This is the method of induction by opposition and conflict, which he used not for laying down doctrines, but for refuting. The method from consequence is twofold: one proving the particular under inquiry through the particular, the other through the universal. And the former is rhetorical, while the latter is dialectical. For instance, in the former it is investigated whether this man committed murder; the proof is that he was found at that time covered in blood.