The Lives and Opinions of Eminent Philosophers

by Diogenes Laertius

The first kind that is not demonstrated, is that in which the whole argument consists of a conjunctive and an antecedent; and in which the first term repeats itself so as to form a sort of conjunctive proposition, and to bring forward as the conclusion the last term. As, for instance, “If the first be true, so is the second; but the first is true, therefore, so is the second.” The second kind that is not demonstrated, is that which, by means of the conjunctive and the opposite of the conclusion, has a conclusion opposite to the first premiss. As, for instance, “If it be day, it is light; but it is night, therefore it is not day.” For here the assumption arises from the opposite of the conclusion, and the conclusion from the opposite of the first term. The third kind that is not demonstrative, is that which, by a negative combination, and by one of the terms in the proposition, produces the contradictory of the remainder; as, for instance, “Plato is not dead and alive at the same time but Plato is dead; therefore, Plato is not alive.” The fourth kind that is not demonstrative, is that which, by means of a disjunctive, and one of those terms which are in the disjunctive, has a conclusion opposite to what remains; as, for instance, “It is either the first, or the second; but it is the first; therefore, it is not the second.” The fifth kind that is not demonstrative, is that in which the whole argument consists of a disjunctive proposition, and the opposite of one of the terms, and then one makes the conclusion identical with the remainder; as, for instance, “It is either day or night; but it is not night; therefore it is day.”

According to the Stoics, truth follows upon truth, as “It is light,” follows upon “It is day.” And falsehood follows upon falsehood; as, “If it is false that it is night, it is also false that it is dark.” Sometimes too, truth follows from falsehood; for instance, though it is false that “the earth flies,” it is true that “there is the earth.” But falsehood does never follow from truth; for, from the fact that “there is the earth,” it does not follow “that the earth flies.”

There are also some arguments which are perplexed, being veiled and escaping notice; or such as are called sorites, the horned one, or the nobody. That is a veiled argument[88] which resembles the following one; “two are not a few, nor three, nor those, nor four, and so on to ten; but two are few; therefore, so are ten few.”

The nobody is a conjunctive argument, and one that consists of the indefinite and the definite, and which has a minor premiss and a conclusion; as, for instance, “If any one is here, he is not in Rhodes.”

L. Such then are the doctrines which the Stoics maintain on the subject of logic, in order as far as possible to establish their point that the logician is the only wise man. For they assert that all affairs are looked at by means of that speculation which proceeds by argument, including under this assertion both those that belong to natural and also those which belong to moral philosophy: for, say they, how else could one determine the exact value of nouns, or how else could one explain what laws are imposed upon such and such actions? Moreover, as there are two habits both incidental to virtue, the one considers what each existing thing is, and the other inquires what it is called. These then are the notions of the Stoics on the subject of logic.

LI. The ethical part of philosophy they divide into the topic of inclination, the topic of good and bad, the topic of the passions, the topic of virtue, the topic of the chief good, and of primary estimation, and of actions; the topic of what things are becoming, and of exhortation and dissuasion. And this division is the one laid down by Chrysippus, and Archedemus, and Zeno, of Tarsus, and Apollodorus, and Diogenes, and Antipater, and Posidonius. For Zeno, of Cittium, and Cleanthes, have, as being more ancient they were likely to, adopted a more simple method of treating these subjects. But these men divided logical and the natural philosophy.

LII. They say that the first inclination which an animal has is to protect itself, as nature brings herself to take an interest in it from the beginning, as Chrysippus affirms in the first book of his treatise on Ends; where he says, that the first and dearest object to every animal is its own existence, and its consciousness of that existence. For that it is not natural for any animal to be alienated from itself, or even to be brought into such a state as to be indifferent to itself, being neither alienated from nor interested in itself. It remains, therefore, that we must assert that nature has bound the animal to itself by the greatest unanimity and affection; for by that means it repels all that is injurious, and attracts all that is akin to it and desirable. But as for what some people say, that the first inclination of animals is to pleasure, they say what is false. For they say that pleasure, if there be any such thing at all, is an accessory only, which, nature, having sought it out by itself, as well as those things which are adapted to its constitution, receives incidentally in the same manner as animals are pleased, and plants made to flourish.

Moreover, say they, nature makes no difference between animals and plants, when she regulates them so as to leave them without voluntary motion or sense; and some things too take place in ourselves in the same manner as in plants. But, as inclination in animals tends chiefly to the point of making them pursue what is appropriate to them, we may say that their inclinations are regulated by nature. And as reason is given to rational animals according to a more perfect principle, it follows, that to live correctly according to reason, is properly predicated of those who live according to nature. For nature is as it were the artist who produces the inclination.

LIII. On which account Zeno was the first writer who, in his treatise on the Nature of Man, said, that the chief good was confessedly to live according to nature; which is to live according to virtue, for nature leads us to this point. And in like manner Cleanthes speaks in his treatise on Pleasure, and so do Posidonius and Hecaton in their essays on Ends as the Chief Good. And again, to live according to virtue is the same thing as living according to one’s experience of those things which happen by nature; as Chrysippus explains it in the first book of his treatise on the Chief Good. For our individual natures are all parts of universal nature; on which account the chief good is to live in a manner corresponding to nature, and that means corresponding to one’s own nature and to universal nature; doing none of those things which the common law of mankind is in the habit of forbidding, and that common law is identical with that right reason which pervades everything, being the same with Jupiter, who is the regulator and chief manager of all existing things.

Again, this very thing is the virtue of the happy man and the perfect happiness of life when everything is done according to a harmony with the genius of each individual with reference to the will of the universal governor and manager of all things. Diogenes, accordingly, says expressly that the chief good is to act according to sound reason in our selection of things according to our nature. And Archedemus defines it to be living in the discharge of all becoming duties. Chrysippus again understands that the nature, in a manner corresponding to which we ought to live, is both the common nature, and also human nature in particular; but Cleanthes will not admit of any other nature than the common one alone, as that to which people ought to live in a manner corresponding; and repudiates all mention of a particular nature. And he asserts that virtue is a disposition of the mind always consistent and always harmonious; that one ought to seek it out for its own sake, without being influenced by fear or hope by any external influence. Moreover, that it is in it that happiness consists, as producing in the soul the harmony of a life always consistent with itself; and that if a rational animal goes the wrong way, it is because it allows itself to be misled by the deceitful appearances of exterior things, or perhaps by the instigation of those who surround it; for nature herself never gives us any but good inclinations.