Zoroastrian . A follower of Zoroastrianism, a monotheistic religion founded approximately four to nine thousand years ago by the Persian philosopher Zarathustra . Traditionally, both lay membership and membership in its priesthood were hereditary; the religion did not accept outside worshippers, nor did it admit children whose parents were not both members of the faith . In 2047, the religion had fewer than 20,000 practitioners, most of them in the Indian city of Bombay .