Zarathustra taught that the universe is ruled by two great powers, Truth and the Lie, or Light and Dark, which battle constantly for control over the world and over the souls of each person. Morality consists in choosing the side of truth and light. So far as we know, Zarathustra was the first to imagine the universe as the battleground of good and evil. He was also the first to imagine that at the end of time there would be a great battle in which good would triumph, ushering in a perfect age. He also taught that there were two different afterlives, and that followers of the Lie would end up in a pit of darkness, while followers of Truth would reside forever in paradise -- which is just the ancient Persian word for garden. You might think, no, that is an obvious idea known around the world, it is part of the human inheritance and can't have been invented by one person. But that is not so. Good and evil have no part in most human cosmologies. This view of the universe was unknown to most civilizations until Zarathustra's teachings entered post-exile Judaism and spread from there to Christianity and Islam and thence around the world. American Indians had no such notion, nor did the Greeks, the Romans, the Australian Aborigines, or anyone else I know of. Most Chinese people still find it puzzling, while advanced Hindu thinkers consider it childish.
This is on my mind because I just finished reading In Search of Zarathustra by Paul Kriwaczek (2002). I loved his more recent book, Babylon, and when I heard about this book I immediately ordered a copy. In Zarathustra Kriwaczek combines history with travelogue, giving us equal parts historical exposition and accounts of visits to archaeological sites from Afghanistan to France. In places it is delightful, but on the whole it does not hold together very well. Breaking up the history according to how it relates to various sites makes for a jumble, and I kept wishing for a narrative in chronological order. Some of the travelogue is also kind of tedious, and only a few of the places really come alive. They also seemed random, more a series of separate visits than one journey. I found the scholarship uneven. Kriwaczek tends to build his narration around the works of one scholar, which sometimes left me with no sense of what is accepted and what controversial. I was unimpressed by his treatment of Roman Mithraism, which devoted more space to his boyhood visit to a temple of Mithras uncovered in 1950s London than to the question of whether Mithraism really had anything to do with Zarathustra's teachings.
(Picture at top shows an ancient Iranian fire temple, the one below a Parsi or Zoroastrian temple in Mumbai, India, built in the eighteenth century.)