Zoroastrianism Spreads

Zoroastrianism, one of the world's oldest continuously practiced faiths, grew from the teachings of the Iranian prophet Zarathustra (Zoroaster in Greek) and became the dominant religion of the Iranian peoples over the following centuries. Its emphasis on a single supreme god, a cosmic struggle between good and evil, and individual moral responsibility shaped religious thought well beyond Iran. The date of 600 BCE is a convenient approximation, since the true timeline of the faith's origins and spread is uncertain.

Zarathustra's own dates are among the most debated questions in the study of ancient religion. Traditional Zoroastrian and Greek sources place him around 600 BCE, but most modern scholars, relying on the archaic language of his hymns, argue he lived much earlier, perhaps between about 1500 and 1000 BCE, somewhere in Central Asia or the eastern Iranian world. Before his teachings, Iranian peoples worshipped a pantheon of nature and ritual deities, related to the gods of early Vedic India, and honored them through sacrifice and fire rites.

Zarathustra's message, preserved in the Gathas, the oldest part of the sacred text known as the Avesta, centered on Ahura Mazda, the "Wise Lord," as the creator of all that is good. Against him stood the destructive principle, later called Angra Mainyu. Humans, in this view, have free will and must choose between truth (asha) and falsehood (druj), a choice that shapes their fate after death. Fire became the central symbol of purity and divine light, and Zoroastrians worship in fire temples.

The spread of the religion was gradual and is poorly documented. It appears to have moved westward across the Iranian plateau, gaining ground in Media and Persia. Under the Achaemenid Empire, founded by Cyrus the Great in the mid-sixth century BCE, Ahura Mazda was clearly venerated by rulers such as Darius I, whose inscriptions praise him. Scholars still debate how far the early Achaemenid kings followed Zoroastrian doctrine as later tradition defines it, and the faith likely varied by region and period. Its status was strengthened under the Parthians and especially the Sasanian dynasty (third to seventh centuries CE), which made it a state religion and organized its priesthood and texts.

The legacy of Zoroastrianism is significant. Many historians see possible influence on Judaism, Christianity, and Islam in ideas such as a final judgment, heaven and hell, and angelic and demonic forces, though the extent of this borrowing is contested. After the Arab conquest of Persia in the seventh century CE, the religion declined in Iran, and some adherents emigrated to India, where they became known as Parsis. Today, small communities survive in Iran, India, and around the world.