As the Monad in religion is an expression of one infinite supreme presence, pervading all nature and life, so the Duad shows the antagonism and conflict between truth and falsehood, right and wrong, good and evil, the infinite perfection and the finite imperfection.  This is a conflict actually existing in the world, and one which religion must accept and account for.  Brahmanism does not accept it, but ignores it.  This whole conflict is Maya, a deception and illusion.  Yet, in this form of illusion, it makes itself so far felt, that it must be met by sacrifices, prayers, penances, and the law of transmigration; until all the apparent antagonism shall be swallowed up in the Infinite One, the only substance in the universe.

Buddhism recognizes the conflict more fully.  It frankly accepts the Duad as the true explanation of the actual universe.  The ideal universe as Nirvana may be one; but of this we know nothing.  The actual world is a twofold world, composed of souls and the natural laws.  The battle of life is with these laws.  Every soul, by learning to obey them, is able to conquer and use them, as steps in an ascent toward Nirvana.

But the belief of Zoroaster and that of Scandinavia regard the Duad as still more deeply rooted in the essence of existing things.  All life is battle,—­battle with moral or physical evil.  Courage is therefore the chief virtue in both systems.  The Devil first appears in theology in these two forms of faith.  The Persian devil is Ahriman; the Scandinavian devil is Loki.  Judaism, with its absolute and supreme God, could never admit such a rival to his power as the Persian Ahriman; yet as a being permitted, for wise purposes, to tempt and try men, he comes into their system as Satan.  Satan, on his first appearance in the Book of Job, is one of the angels of God.  He is the heavenly critic; his business is to test human virtue by trial, and see how deep it goes.  His object in testing Job was to find whether he loved virtue for its rewards, or for its own sake.  “Does Job serve God for naught?” According to this view, the man who is good merely for the sake of reward is not good at all.

In the Egyptian system, as in the later faith of India, the evil principle appears as a power of destruction.  Siva and Typhon are the destroying agencies from whom proceed all the mischief done in the world.  Nevertheless, they are gods, not devils, and have their worship and worshippers among those whose religious nature is more imbued with fear than with hope.  The timid worshipped the deadly and destructive powers, and their prayers were deprecations.  The bolder worshipped the good gods.  Similarly, in Greece, the Chtonic deities had their shrines and worshippers, as had the powers of Blight, Famine, and Pestilence at Rome.