The Lives and Opinions of Eminent Philosophers by Diogenes Laërtius (best free ebook reader txt) 📕

speculative, the other practical; and of these two again, the speculative is divided into the natural and the logical, and the practical into the ethical and the political. Again, the kind fitted for investigating has also two primary divisions with their separate characteristics: one object of which is simply practice, the other being also disputatious; and the first of these two is again subdivided into two: one of which may be compared to the art of the midwife, and the other is as it were tentative; the disputatious one is also divided into the demonstrative and the distinctive.

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 Timaeus. Of the logical class, there are the Politics, the Cratylus, the Parmenides, and the Sophist. Of the ethical kind there is the Defense of Socrates, the Crito, the Phaedo, the Phaedrus, 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 Alcibiadeses, the Theages, the Lysis, the Laches. Of the tentative kind, there is the Euthyphro, the Meno, the Ion, the Charmides, and the Theaetetus. Of the demonstrative description, we have the Protagoras, and of the distinctive class the Euthydemus, the two Hippiases, and the Gorgias. And this is enough to say about the dialogues as to what they are, and what their different kinds are.

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, Timaeus, 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 Timaeus. 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