As we shall see, the fundamental principle of the religion of Zarathrustra is that a supreme god stands over all gods, and to him is ascribed the work of creation. In entire belief in the power of this supreme deity, whom the Achæmenids invoke by the name which is given to him in the Avesta, "who has created heaven and earth and all that is good for men," Darius ascribes to Auramazda victory in battles, the power of granting or refusing success to the king's undertakings, of protecting the land against hostile invasions, blight, and lies. To those who live according to his commands he grants long life and numerous descendants. The rebellion of the provinces is with Darius the work of the lie, the lie of him who had given himself out to be the son of Cyrus, and the lie of those who had claimed to be the descendants of Nebuchadnezzar and Cyaxares. We have already observed what "the lie" meant in the Avesta. In the same spirit – the spirit of the principal rules of the Avesta – Darius adjures his Persians to think no evil, and not to leave the right path.

Nicolaus of Damascus assures us that the Persians were acquainted with the sayings of Zoroaster. He and others relate that Cyrus or his father was called Atradates, i. e. given by fire,¹⁶⁸ and that he had given to the Areians (p. 11), who provided his famished army with sustenance, the honourable title of Orosangians, i. e. Huverezànha (benefactors). It is in harmony with the doctrine of the Avesta that Cyrus should be represented by such a descent or name as the gift and nursling of fire, and we shall see with what emphasis the Avesta marks and distinguishes good thoughts, words, and actions. From these facts and the inscriptions of Darius there can be no doubt that Zarathrustra's doctrine was current among the Persians at the time of Cyrus. But if it was in force in the West of Iran in the sixth century B.C. the fact that Herodotus, in his account of the period during which the Medes obtained the dominion, down to the time of Cyrus, speaks of no change in religion, either among the Persians or the Medes, is evidence that this religion existed at any rate before the time of Phraortes. The statement found in Herodotus that Deioces had forbidden any one to spit in his presence, reminds us of the rules of the Avesta, by which no one was allowed to approach the sacred fire and gods with uncovered mouth, and on the sculptures of Persepolis the bearer of the fan stands with covered mouth beside Darius. The seven walls which Herodotus represents Deioces as building round Ecbatana, the seven tribes of the Persians, remind us of the seven girdles of the earth in the Avesta; the king of the Persians surrounded by the six tribal princes is the symbol of Auramazda and the six gods who are about him.

Hence we may assume that the doctrine of Zarathrustra had reached the West of Iran at the time when Phraortes united the tribes of the Medes (about 650 B.C.), and was known among the Medes when they were still living under their tribal chiefs and paid tribute to Asshur, or, in case of refusal, were attacked by the Assyrian armies, which, as we ascertained from the inscriptions of the kings of Asshur, was the case from the time of Tiglath Pilesar II. to the time of Assurbanipal, i. e. from the middle of the eighth to the middle of the seventh century B.C. A statement in Herodotus seems to lead us still further back. He calls the Magians a race or tribe of the Medes. According to his narrative this tribe was in existence in the time of Deioces, i. e. about the year 700 B.C. Herodotus could only speak of the Magians as a tribe or family when they had become an hereditary order. At that time, therefore, there must have been among the Medes a priesthood who perpetuated in their families their worship by sacrifice, their doctrine and wisdom, as well as their social importance. Like all Greeks, Herodotus ascribes the discharge of the religious functions among the Persians and Medes to the Magians, and we find that what Herodotus quotes of their rites agrees with the rules of the Avesta. The rise and separation of a peculiar order of priests, their more or less sharply marked distinction from the remaining orders, can never be the work of a short space of time, and such separation can only take place when the worship of the gods requires a knowledge which is not easily accessible or obtainable, when doctrine has obtained a place by the side of belief, when ritual has become developed, and particular duties and rules are prescribed for the life of the priests. When the worship of the gods requires the use of long and definite prayers, the knowledge of complicated usages, on which depends the effect of the sacrifices, and the observation of numerous rules of purification, – such knowledge is only perpetuated in families of hierophants or priests, or in schools which take the place of such families. The formation of a distinct hereditary order on such grounds can hardly have occupied less than a century from the time when the doctrine, on which it is formed, was introduced. Hence we may assume that the doctrine known as Zarathrustra's reached the Medes before the year 750 B.C., i. e. before the date of Tiglath Pilesar II. of Assyria.

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.

Can we go beyond the result thus gained by our investigation? – that the doctrine of Zoroaster flourished in Eastern Iran about 800 B.C., and advanced towards the West from this period; may we assume that at this date it was already in possession of written monuments, and even that the fragments of the Avesta which still remain were in existence then? We must first answer the question whether the use of writing in Iran, especially in the East, goes back so far.

According to the statements of Herodotus, the West of Iran was not only in possession of the art of writing by the year 700 B.C., but made considerable use of it. He tells us that Deioces required complaints to be sent in to him in writing, and gave out his decisions also in writing. If processes at law were conducted in writing in Media about the year 700 B.C., it cannot be surprising that Herodotus should also inform us that letters passed between Media and Persia about the year 560 B.C.¹⁷³ We learn from the Hebrew Scriptures that when Cyrus allowed the Jews, whom Nebuchadnezzar had removed to Babylon, to return to their homes, he gave his permission for the restoration of the temple in writing. This document was afterwards discovered in the archives of Ecbatana.¹⁷⁴ We know it for a fact that Darius I. gave his orders to the satraps in writing, and we are acquainted with the seal of Darius by which they were authenticated. The oldest inscriptions which have come down to us from the Achæmenids, not to mention a seal of Cyrus from Senkereh, belong, if not to Cyrus himself, to Darius, and begin about the last quarter of the sixth century B.C. It is the cuneiform writing of Assyria and Babylon which forms the basis of the writing in these inscriptions, but with considerable alterations. The highly complicated syllabarium of the Eastern Semites is reduced to a phonetic system; we might almost say to an alphabet of about 40 letters. A change of this kind can hardly have been made at one stroke. If it was after they entered into closer combination with Assyria, i. e. after their dependence on the king of Asshur, which began with the accession of Tiglath Pilesar II. (745 B.C.), that the Medes became acquainted with the Assyrian system of writing, this must have been completely mastered before it could be abbreviated and altered, as it was altered by the Medes, whose changes were adopted by the Persians. The cuneiform writing of Western Iran, as we find it in the inscriptions of Darius, can therefore hardly have been established before the year 600 B.C. However this may be, the facts mentioned prove that the writing of the Assyrians in the seventh century B.C. was not unknown in the West of Iran. This would therefore have passed into the East of Iran in its original or simplified form, either at some earlier period, or when the East came under the dominion of the Achæmenids. But it did not, and this is a plain proof that the East, when the cuneiform writing of the West came in that direction, was already in possession of another kind of writing. This Eastern mode of writing, the Arian, which rests on an entirely different basis from the cuneiform, is first known to us from coins and inscriptions of the third century B.C.; but it certainly would not have maintained its ground under the Achæmenids against the writing of the West, and of the rulers, magistrates, and dominant nation, unless it had been in vigorous use before, this period. We must therefore assume that the Arian character was in use in the East of Iran a considerable time before the date of Cyrus, and hence we have no reason to deny the existence of it in that region in the eighth century B.C., since we must allow the neighbouring Arians of India to have been in possession of their written characters from the year 800 B.C. at the least (IV. 155).

If we may assume that the Arian character was in use in the East of Iran about the year 800 B.C., the prayers and sayings of Zarathrustra might have been written down about this date, and the doctrine might have passed on to the West supported by written documents. But the fact that the prayers might have been written down is in no way a proof that they were so written.

It is true that at first sight it seems that the part of the law which has come down to us (the Vendidad) leads to the conclusion that it was written down long before the Persians gained the dominion over Iran, and Media became a powerful state under Cyaxares. The book does not mention the name of the Persians or the Medes, of Ecbatana or Persepolis, while Bactria is spoken of as the seat of the empire; the most westerly district mentioned in the Vendidad is Ragha in Eastern Media.¹⁷⁵ If we add that the book reproaches certain districts in the East, the land of the Arachoti and others, with deviations from the doctrine of Zarathrustra, and that Ragha is indeed Zoroastrian but wavering in its fidelity, we may easily conclude that the Vendidad was written when the doctrine of Zarathrustra had not as yet thoroughly penetrated the East, and was still unknown in the West, when it had just reached, but had not yet completely conquered, the district of Ragha. The Medes were still dependent on Asshur, living separately according to their tribes, Ecbatana was not yet the centre and metropolis of Media, and the kingdom of Bactra was still in existence in the East. This points to a date about 750 B.C. as the time when this doctrine must have spread widely over Media; at any rate to a date before the rise of the Median power, i. e.