The Persian was an active people, making war on surrounding nations and fighting to extend the dominion of Ahura-Mazda and to gain a victory over Ahrimanes. The Hindu, on the other hand, in his education, cultivates abstract contemplation and meditation, and does not believe in wars or conflict. The child must be taught how to attain the blessedness of passivity and repose. No active duties for him—no struggles to overcome nature, to slay wild beasts or exterminate the pests of the earth, but he must be mild, and spare animal life, even in tigers, serpents, scorpions, and vermin. The Persian education fits the youth for a career of active warfare against wild beasts and all unclean animals. Clean animals are such as are in the service of light and truth and purity and cleanliness. The unclean do not serve Ahura-Mazda, but darkness and evil and filth and foulness. Unclean beasts are supposed to be tenanted by evil spirits in the service of Ahriman. Not only the horse and cow, but the hedgehog, who roams about at night when evil spirits are abroad, and the beaver, who kills the evil beings in the water, are clean animals. All scavenger animals—all carrion birds also serve Ahura-Mazda. This principle of good and evil seems to have been at first the principle of light and darkness only. It would seem that Zoroaster converted what was a principle of nature into a spiritual principle. The religion of the Brahmins was also a religion based chiefly on the same distinction of light and darkness, in the early times before their migration from the high table-lands of Bactria, to the southeast, to the Indus valley. But the Brahmin, given to abstract thinking, ascended to the idea of a supreme unity as the origin and final destiny of his Vedic gods of the sky, while the Persian changed light and darkness to moral principles of good and evil, and made their difference more substantial than their unity.