AHRIMAN. - In the Mazdean religion he is the evil principle, the one from which every evil originates, also called in older forms angro mainyush. The second part of the compound mainyush means "spirit"; the meaning of the first part, angro, is still disputed, probably it is equivalent to "tormentor, maleficent," as opposed to spento mainyush "beneficent spirit."
In the ancient Avesta he is opposed not directly to Ahuramazda, but rather to his "beneficent spirit." The one and the other, the tormentor and the beneficent one, are called "twins" (Yasna 30, 3), yet they always stand in opposition, agreeing neither in thought, nor in decisions, nor in speech, nor in action (Yasna 45, 2). In the later development of the religion the beneficent spirit came to be identified with Ahuramazda, a development whose beginnings can be noted even in the ancient hymns; and then there arose a direct dualism between Ahuramazda and A. Aristotle already knows this stage of development, when he directly opposes Oromasdes and Areimanus (Diogenes Laertius, Vita philos., proem. 5). The name Angro mainyush occurs a couple of times in the ancient Avesta; more often evil is represented in it by druj, "lie," from which the evil teacher, that is the heretic, and the mendacious tongue draw inspiration, and from which ignorance of right doctrine takes its origin. No creation is attributed to the evil spirit; by free choice men determine themselves for the one or the other spirit, and thus there is on earth dualism and the struggle between good and evil. The devas, that is the deities of the ancient Iranian polytheism that Zarathustra fought against, chose the evil principle and became demons.
In the course of the cosmic age, the one and the other spirit each have their own power, but at the end of the world the good principle will triumph definitively over the evil one.
In the recent Avesta and in the later religious literature A. is given a creation opposed to that of Ahuramazda; while the latter creates life and light, he creates death and darkness. To annihilate the good creatures he makes use of a frightful monster, Azhi Dahaka, he throws the course of the stars and that of the waters into confusion in order to make the earth barren, he sends countless diseases to torment men. He dwells in the darkness, and on earth he gathers his diabolical hosts on Mount Arezura, draws them up for the assault and hurls them into the world. He can transform himself into a horse, a toad and a serpent. In the Pahlavi literature, which draws on lost books of the Avesta, his struggle against Ahuramazda is enclosed within a chronological system of twelve thousand years, divided into four periods of three thousand years. With the beginning of the third period of three thousand years the struggle is kindled, and A. succeeds in killing the first man, Gayomart, and the first-born bull, the prototype of animal and vegetable life, and there is on earth a mixture of good and evil following the irruption of the evil spirit. At the end of the last period of three thousand years he will be defeated, evil destroyed; good, on the other hand, will have uncontested dominion.