Zoroastrianism is a religion that developed in Iran from about the sixth century BC, generally ascribed to Zoroaster (Zarathustra), who was born in Iran '258 years before Alexander.' The date of Zoroaster's birth has been given variously as 6000 BC, 1400 BC, and 1000 BC, but Herzfeld accepts the traditional date, approximately, as now confirmed (Herzfeld, (570 - 500 BC); Jackson, 660 - 583 BC). Accordingly, Zoroaster was contemporary with other great religious personages, including Buddha, Confucius, Lao Tze, and several Hebrew prophets. That Zoroaster used Vedic materials found in early Hinduism can hardly be denied; that he was a polytheist like Darius, Xerxes, and others who were probably Zoroastrians (at least, their inscriptions pay homage to Ahura Mazda) seems most likely.
But Zoroaster was protesting against the false and cruel in religion, and followed the principle, "If the gods do aught shameful, they are not gods." Accordingly, he exalted Ahura Mazda ("wise Lord," often improperly translated "Lord of light") as supreme among the gods or spirits, and viewed the world as an agelong struggle between Ahura Mazda and Angra Mainy (or Ahramanyus, Ahriman, "Spirit of evil"), both of whom came into existence independently in the distant past. Zoroastrianism is therefore called a dualism, but it is a limited dualism.
Zoroaster calls upon human beings to join in this conflict on the side of Ahura Mazda, the key words of such religion being "good thoughts, good works, good deeds." The ultimate victory of Ahura Mazda, however, was not to be accomplished by human assistance but by the advent of a messiahlike figure, the Saoshyant. The duration of the struggle was to be six thousand years (three thousand had already passed when Zoroaster was born), following which was to be the resurrection and judgment. Many of the details of Zoroastrianism are later developments, some post Christian and even post Mohammedan, and scholars are divided on what elements are to be traced to Zoroaster's own teaching.
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