In view of the mixed good and evil in the world, thinkers of antiquity, outside of Israel and before the rise of the Stoic philosophy in Greece, could not conceive the universe as being set in motion and directed by one God infinite at once in power and goodness. Even the most penetrating intellect of Greece faltered in his search for unity: “We cannot suppose,” says Plato, “that the universe is ordered by one soul; there must be more than one, probably not less than two--one the author of good, and the other of evil.”[302] The seers of Israel alone reached with perfect conviction the height of the great argument, and announced confidently that He who is the author of the good in the world is the author likewise of the evil: “I form the light and create the darkness; I make peace and create evil,” are the words which the prophet Isaiah puts in the mouth of Yahweh.[303] The religious thinkers of Persia never reached this lofty viewpoint. It seemed to them, as it seemed to the Greek philosopher, that at least two deities must have been concerned in the creation and ordering of the universe. They believed in the existence of two great powers: a good being, Ahura Mazda, the creator of light and of all beneficent things; and an evil being, Ahriman, the author of darkness and of all baneful creatures. Between these two powers they conceived to be going on a fierce struggle for the mastery, in which ultimate victory was assured to the good Ahura.[304] This Persian world philosophy reacted favorably upon the moral character, and, as we shall see further on, contributed to create in ancient Persia a deep consciousness of the eternal distinction between good and evil, a profound sentiment of duty, and an active, strenuous morality.[305] It is when contrasted with the world philosophy of Brahmanism and Buddhism that the ethical value of this dualistic philosophy of the old Persian thinkers is best disclosed. [Sidenote: Conception of the character of the supreme god, Ahura Mazda] While it is true that the moral qualities attributed by a people to their gods are nothing more nor less than the moral qualities possessed or revered by this people themselves, still it is also true that the moral nature thus given to the gods reacts powerfully upon the ethical life of their worshipers and tends to mold their moral character after the heavenly type. In a word, celestial morality is at once effect and cause.