After the fourth-century CE, Zoroastrianism was the official and publicly supported religion of the Sasanian empire, and the creed to which conquered peoples occasionally were converted by force. Zoroastrianism, just as Christianity, Judaism and Islam, is a monotheistic religion, a religion with only one god, and Zoroastrians call their deity Ahura Mazda, translated as “enlightened wisdom.” Zoroaster, or Zarathustra, the original founder of the faith, came from a line of Persian priests, and was born northeast of the Caspian Sea, most probably some 1,200 BCE. Zoroaster was the author of the Yazna, a book of hymns and incantations. The religion taught in the Yazna makes a sharp distinction between good and evil, and the task of the faithful is to learn to distinguish the two and to choose the good. Like other monotheistic religions, Zoroastrianism grapples with the question of how the belief in one god can be combined with the existence of evil in the world. After all, an all-powerful god should not allow evil to exist. The Zoroastrian answer is that good and evil are choices which confront human beings and not entities that compete for power. Ethical questions, questions of correct conduct, are consequently a crucial part of the faith. Zoroastrianism teaches that all human beings one day will be judged on the basis of the choices they make and either saved or condemned. Zoroastrian rituals rely heavily on fire which is regarded as a holy force, and fire temples, attended by priests, were constructed and officially sponsored throughout the Sasanian empire.
Zoroastrianism had a powerful influence on the other monotheistic religions of the Middle East. Indeed by making the earlier Persian gods into aspects of Ahura Mazda – into spirits through which Ahura Mazda is expressed – Zoroastrianism became the very first monotheistic religion. Its main themes – questions of the afterlife and the end of the world, issues of judgment and salvation – feature prominently in Judaism, Christianity and Islam too, and they all have the same obsession with questions of ethics and good conduct. Moreover, Zoroastrianism was the first religion which regarded people as equals before god, and gave every believer the opportunity to attain salvation. Zarathustra talked about himself as the “savior” much as Jesus Christ was later to do. Yet Christianity and Islam were to become far more popular than Zoroastrianism, not least since the empires that embraced them were more militarily successful than the Sasanians. Although the conversion took several centuries to accomplish, some 95 percent of Zoroastrians eventually switched to Islam. And yet Shia Islam, which is the dominant denomination in Iran, has retained important features of Zoroastrianism, above all the insistence that one day a new imam, the twelfth imam, will appear to judge and save mankind.
There are still Zoroastrians today, although they are not many. In Iran an official census has counted less than 30,000 believers. Today India is the country with the largest official population of Zoroastrians but even here they are less than 70,000 believers. In addition, Iraq has a population of some 700,000 Yazidis, a community of Kurds who practice their own heterodox version of Zoroastrianism. The Yazidis have often been accused by their Muslim neighbors of being worshipers of Satan and persecuted for their beliefs. Yet the Persian new year, Nouruz, which was central to the Zoroastrian faith, is still the most important holiday in Iran and in all other areas once dominated by Zoroastrianism. Indeed, on occasions when the mandatory fasting required by the Muslim holy month of Ramadan has come into conflict with the 18 days of festive celebrations required by Nouruz, the Zoroastrian tradition has prevailed.