In its origins Zoroastrianism appears to have been the religious expression of the peaceful, sedentary communities of N Iran as opposed to the animistic polytheism of their enemies, the nomadic horsemen. Zoroaster consistently contrasts these two peoples as the People of Righteousness ( asha ) and the People of the Lie ( druj ). The religion was concerned with increasing the harvest and with protecting and treating kindly the domestic animals whose labors accomplished the production of food.
Gradually certain practices that Zoroaster appears to have deplored, such as the use of haoma (a narcotic intoxicant) in prayer and the sacrifice of bulls in connection with the cult of the god Mithra (a lesser god in Zoroastrianism), became features of the religion. It is not surprising, however, that former customs should be thus revived, because Zoroaster appears to have incorporated in his religion the old Persian pantheon, although very much refined. Instead of tolerating the worship of all the deities, however, he divided them into those who were beneficent and truthful and those whose malevolence and falseness made them abhorrent.
Heading the good spirits was Ahura Mazdah (also Ormazd or Ormuzd) [sovereign knowledge], in primitive Zoroastrianism the only god. Six attendant deities, the Amesha Spentas, surround him. These abstract representations, formerly the personal aspects of Ahura Mazdah, are Vohu Manah [good thought], Asha Vahista [highest righteousness], Khshathra Vairya [divine kingdom], Spenta Armaiti [pious devotion], Haurvatat [salvation], and Ameretat [immortality]. In time the Amesha Spentas became archangelic in character and less abstract. Opposing the good ahuras were the evil spirits, the daevas or divs, led by Ahriman. The war between these two supernatural hosts is the subject matter of the fully developed cosmogony and eschatology of Zoroastrianism.
The entire history of the universe, past, present, and future, the religion teaches, is divided into four periods, each of 3,000 years. In the first period there was no matter; the second preceded the coming of Zoroaster; and in the third his faith is propagated. The struggle between good and evil rages during the first nine millennia, and humans help Ahura Mazdah or Ahriman according to whether their conduct is good or evil. Each person after death crosses the Chinvato Peretav [bridge of the separator], which spans hell. If he is reprobate, the bridge narrows and he tumbles to perdition, but if he is worthy of salvation he finds a wide road to the realm of light. In the fourth period of the universe a savior, Saoshyant, will appear, the dead will rise for their final reward or punishment, and good will reign eternally.
Zoroastrianism should be regarded as quasi-dualistic, rather than (as sometimes described) wholly dualistic, since it predicts the ultimate triumph of Ahura Mazdah. This god may be represented in the form of the pure natural substances that he has created, notably fire but also water and earth. The special veneration shown to fire and its use in religious ceremonies has led to the erroneous belief that the Zoroastrians were fire worshipers. The care taken to avoid contaminating these natural substances led to great elaboration of the purification ritual.