What did Zoroastrians believe, and did their ideas shape other religions?

Zoroastrians believe in one supreme, wise god, Ahura Mazda, and in a struggle between truth and the lie in which every person must choose a side. Whether those ideas shaped other religions is debated: some scholars say yes, others say the link is much weaker than often claimed.

Zoroastrianism is an Iranian religion centred on the Avesta and the teachings of Zarathushtra Spitama, better known by the Greek form of his name, Zoroaster. Its followers revere Ahura Mazda as an uncreated, benevolent and all-wise being. We do not know when Zoroaster lived: estimates of the religion's founding range from 2000 BCE to "200 years before Alexander".

In the Gathas, the oldest hymns, the central dualism is a moral one. It is the choice between Asha, truth and order, and Druj, chaos and the lie. The central moral precepts are good thoughts, good words and good deeds. A stricter picture, with an evil spirit as a co-equal enemy of Ahura Mazda, appears later, in Middle Persian texts such as the 9th-century Bundahishn.

Fire is particularly sacred as a symbol of Ahura Mazda, and it gives Zoroastrian places of worship their name: fire temples. But the temples came late. According to Herodotus, in the mid-5th century BCE Zoroastrians worshipped under the open sky, climbing mounds to light their fires.

For about a thousand years it was the official religion of Iranian states, from the Achaemenid Empire to the Sasanian Empire. As for influence, Mary Boyce wrote that Zoroaster was the first to teach individual judgement, Heaven and Hell, resurrection and a last judgement. Other scholars disagree, finding its influence much more limited and no link in Jewish or Christian texts.