The most important of the Iranian religions is Zoroastrianism some times also called Mazdaism and Parsiism -which was founded by the prophet Zoroaster. The prophet of ancient Persia reformed the existing Aryan beliefs and established a religion, which soon became the official religion of the Achaemenian Empire. There is still no agreement about the dates of Zoroaster's life; some think that he lived about a thousand BC whereas many other noted scholars believe that he lived from 660 to 583 BC It is in any case known that at the age of twenty Zoroaster withdrew from the world and spent ten years in meditation. At the age of thirty he had a vision in which he was taken before the divine throne and directed to preach the new religion. At first Zoroaster had little success until, suddenly, a Persian king with all of his courtiers adopted the faith. From that moment on the religion became securely established not only in Persia but also in Central Asia. Zoroaster died having brought a religion that dominated the life of Persia for thirteen hundred years through the Sassanian period.
Zoroastrianism, like the other Iranian religions, is famous as being dualistic. Dualism, that is, belief in two opposing realities that dominate the universe, is in fact characteristic of the Iranian religious mind before the Islamic period. In Zoroastrianism there is a belief in Ahura Mazda, the source of all goodness, purity and light, and Ahriman, the source of all evil and darkness. There is a great ethical stress in this religion, and the Zoroastrians believe that these two forces of good and evil are in constant struggle until finally goodness become victorious. In fact, this world exists only as a stage for this important struggle and all human acts have a moral character which bear upon this cosmic battle. Although in the Sassanian period there was a tendency in the religious movement called Zurvanism to interpret Zoroastrianism in a unitary sense, the dualistic view of things was too deep- rooted not to continue to survive in one form or another.
The Zoroastrians also laid great emphasis on angels and had a firm belief in a purely spiritual world separated from matter that stood between Ahura Mazda and this world. They believed in an elaborate system of angelic beings and believed that an angel governs each species in this world. They moreover named each month after an angelic being. The Persian months to day bear the names of the Zoroastrian angels. Angels werconsidered as guardians of both nature and man and as the army of Ahura Mazda arrayed against the forces of Ahriman.

According to Zoroastrian teachings, before man's creation the forces of light and darkness were separate from each other. During the history of the world they engage in a fierce struggle which will terminate with the destruction of the forces of evil and final triumph of good. There was a firm belief in Zoroastrianism in life aher death, judgement of the soul, heaven and hell, and resurrection and the final day of judgement. In these respects, this religion bears a close resemblance to both Christianity and Islam. The moral teachings of Zoroastrianism have been summarized in the motto: "Good thoughts, good words, good deeds". The Zoroastrians laid great emphasis on purity, both inward and outward, and in their religious rites emphasized the purity of the elements. Indeed, in order not to defile the earth they even refused to bury their dead, preferring to leave their dead on top of certain hills set apart for this purpose.
The sacred book of the Zoroastrians is the Avesta. which they have always chanted in their rites. The A vestan language is one of the oldest Indo-European laguages, and the book itself is one of the great religious classics of the world. It is replete with moral teachings as well as instructions concerning religious rites and duties.
Since Ahura Mazda is light, the Zoroastrians considered fire as sacred. In their temples to this very day there is afire that burns continuously, and in general they have had a special love for light in all its forms. That is why they have sometimes been referred to as fire-worshippers. Actually they have never worshipped fire, but have respected it as a symbol of Ahura Mazda. With the rise of Islam and its spread in Persia, Zoroastrianism gradually lost ground until it became restricted to a small minority who still follow this ancient faith in modern Iran. Also a number of Zoroastrians immigrated to India where they thrive today and are known as Parsis. But there, too, their number is limited so that today Zoroastrianism, despite its great historical importance, has only a relatively modest following.