Zarathustra

No major religious founder has a less certain date. Estimates for Zarathushtra range from roughly 1500 BCE to the sixth century BCE, and the gap is not a rounding error.

The traditional Zoroastrian date places him 258 years before Alexander, which yields the early sixth century BCE. That figure appears in late sources and is widely regarded as a construction, possibly built backward from the Seleucid era. Against it stands the linguistic argument, which most specialists now find decisive: the Gathas, the seventeen hymns attributed to him personally, are in an archaic Avestan closely comparable in grammar and vocabulary to the language of the Rig Veda. If the Rig Veda belongs to the second millennium BCE, so plausibly does Gathic Avestan. The society the Gathas describe, pastoral, chariot-using, with no cities, no writing, no Persians and no Medes, points the same way.

Mary Boyce argued for a date as early as 1500-1200 BCE. Others place him around 1000 BCE. A minority continue to defend a later date, and Almut Hintze and others have argued the linguistic evidence is less conclusive than it appears because archaic religious language can be preserved artificially.

The place is equally open, somewhere in eastern Iran or Central Asia rather than in the Persian southwest.

What is not in doubt is the Gathas themselves. They are difficult, dense, and in the first person, and they present a man arguing with rival priests, complaining that he has no support and few cattle, and asking Ahura Mazda direct and rather aggrieved questions.

Zoroastrianism is regularly credited with supplying Judaism, Christianity and Islam with a cluster of ideas, a cosmic opponent of God, angels and demons in ranks, a final judgement, resurrection of the body, heaven and hell, a saviour to come at the end. The claim is old, it is not baseless, and it is asserted far more confidently than the evidence supports.

The difficulty is dating on both sides. The distinctively Zoroastrian eschatology is fully documented only in Middle Persian texts of the ninth century CE and later, written after the Islamic conquest, by which time contact and mutual influence had been running for a very long time. The Avestan material is earlier but much of it is liturgical rather than systematic, and the great compendia are lost. Meanwhile the Jewish material develops in the Persian period and after, which is when the two communities were in contact under the Achaemenids, so the chronology is compatible with influence, and compatible with the reverse, and compatible with parallel development.

Angra Mainyu in the Gathas is not the mirror of Ahura Mazda. He is opposed to Spenta Mainyu, the beneficent spirit, and the two are presented as twin mentalities choosing between truth and the lie. The strict two-power cosmology of later Zoroastrianism is a development, and Zurvanism is a further variant that the tradition later repudiated.

The defensible statement is that the parallels are real and the direction of borrowing is not established for any specific doctrine. Specific claims should be attributed to whoever is making them.