Let us hold firmly to the facts that the worship of Auramazda was current among the Persians about the middle of the sixth century B.C., that the same worship was in force among the Medes at least a century earlier, about 650 B.C., and that if an hereditary priesthood was in existence about this time among the Medes who performed and conducted the worship, the doctrine which this priesthood represented must have been adopted before the year 750 B.C. In this way we obtain a proof that the doctrine of Zarathrustra was not only in existence in the East of Iran about the year 800 B.C., but was the dominant creed there, and had force enough to penetrate to the West, and win over the neighbouring tribes of the Medes and Persians. We cannot explain more exactly how the doctrine of Zarathrustra reached the nations of the West of Iran. Pliny, it is true, exclaims: "Who knows the Medes, who were taught by Zoroaster, Apusorus, and Zaratus, even by hearsay, for no memorials of them are left?"[169] According to this the religion of Zoroaster spread even in the West by the influence of eminent men among the Medes. But the date of the persons mentioned cannot be fixed, though Porphyry represents Pythagoras as going to the Chaldæans and Zabratus, by whom he was purified from the evil of his former life, and instructed as to the things from which the disciple should restrain himself, and about the nature and beginning of all things,[170] and this Zaratus or Zabratus may be intended for Zarathrustra himself. Hermodorus tells us that Zarathrustra had been followed by many Magians as teachers, one after the other, down to the time when Alexander marched against Persia: these teachers were Osthanes, Astrampsychus, Gobryas, and Pazates.[171] Others also assert that Zoroaster was followed "by Osthanes and Astrampsychus."[172] Pliny observes that so far as he could discover, Osthanes who accompanied Xerxes in the war against the Hellenes, was the first who had written on the doctrine of the Magians. The second Osthanes, whom Alexander had received among his followers, had caused this religion to be of great importance. From the work of one of these two persons, Philo of Byblus quotes a passage--the work he calls the Octateuch--and Pliny notes down apparently some of the doctrines of the first Osthanes. If then there were men under the Achæmenids in the West of Iran who could write on the doctrine of Zarathrustra from the beginning of the fifth century B.C., we can without hesitation believe the statement that long before this time there were prophets and teachers of the doctrine among the Medes and the Persians.