These were the doctrines of the Stoics, from whose sublime and impracticable philosophy they seemed naturally enough to flow. Aulus Gellius relates that the last-mentioned argument was expounded by Chrysippus, in his work upon providence. The answer given by Plutarch seems quite sufficient: “As well might you say that Achilles could not have a fine head of hair unless Thersites had been bald; or that one man’s limbs could not be all sound if another had not the gout.” In truth, the Stoical doctrine proceeds upon the assumption that all virtue is only the negative of vice; and is as absurd, if indeed it be not the very same absurdity, as the doctrine which should deny the existence of affirmative or positive truths, resolving them all into the opposite of negative propositions. Indeed, if we even were to admit this as an abstract position, the actual existence of evil would still be unnecessary to the idea, and still more to the existence, of good. For the conception of evil, the bare idea of its possibility, would be quite sufficient, and there would be no occasion for a single example of it. The other doctrine, that of two opposite principles, was embraced by most of the other sects, as it should seem, at some period or other of their inquiries. Plato himself, in his later works, was clearly a supporter of the system; for he held that there were at least two principles, a good and an evil; to which he added a third, the moderator or mediator between them. Whether this doctrine was, like many others, imported into Greece from the East, or was the natural growth of the schools, we cannot ascertain. Certain it is that the Greeks themselves believed it to have been taught by Zoroaster in Asia, at least five centuries before the Trojan war; so that it had an existence there long before the name of philosophy was known in the western world. Zoroaster’s doctrine agreed in every respect with Plato’s; for besides Oomazes, the good, and Arimanius, the evil principle, he taught that there was a third, or mediatory one, called Mithras. That it never became any part of the popular belief in Greece or Italy is quite clear. All the polytheism of those countries recognized each of the gods as authors alike of good and evil. Nor did even the chief of the divinities, under whose power the rest were placed, offer any exception to the general rule; for Jupiter not only gave good from one urn and ill from another, but he was also, according to the barbarous mythology of classical antiquity, himself a model at once of human perfections and of human vices.