The Mazdean system, or worship of Ahura Mazda (Ormazd), of which we find in Herodotos positive historical record as an anti-idolatrous and nominally monotheistic creed90 in the fifth century B.C., is the first to which these aspects can be ascribed with certainty. As the Jews are found represented in the Book of Jeremiah91 (assumed to have been written in the sixth century B.C.) worshipping numerous Gods with images: and as polytheistic and idolatrous practices are still described in the Book of Ezekiel92 (assumed to have been written during or after the Babylonian Captivity), it is inadmissible to accept the unauthenticated writings of ostensibly earlier prophets as proving even a propaganda of monotheism on their part, the so-called Mosaic law being known to be in large part of late invention and of Babylonian derivation.93 In any case, the mass of the people were clearly image-worshippers. The Persians, on the other hand, can be taken with certainty to have had in the sixth century an imageless worship (though images existed for other purposes), with a supreme God set above all others. The Magian or Mazdean creed, as we have seen, was not very devoutly held by Cyrus; but Dareios a generation later is found holding it with zeal; and it cannot have grown in a generation to the form it then bore. It must therefore be regarded as a development of the religion of some section of the “Iranian” race, centering as it does round some deities common to the Vedic Aryans.

The Mazdean system, as we first trace it in history, was the religion of the Medes, a people joined with the Persians proper under Cyrus; and the Magi or priests were one of the seven tribes of the Medes,94 as the Levites were one of the tribes of Israel. It may then be conjectured that the Magi were the priests of a people who previously conquered or were conquered by the Medes, who had then adopted their religion, as did the Persians after their conquest by or union with the Medes. Cyrus, a semi-Persian, may well have regarded the Medes with some racial distrust, and, while using them as the national priests, would naturally not be devout in his adherence at a time when the two peoples were still mutually jealous. When, later, after the assassination of his son Smerdis (Bardes or Bardija) by the elder son, King Cambyses, and the death of the latter, the Median and Magian interest set up the “false Smerdis,” Persian conspirators overthrew the pretender and crowned the Persian Dareios Hystaspis, marking their sense of hostility to the Median and Magian element by a general massacre of Magi.95 Those Magi who survived would naturally cultivate the more their priestly influence, the political being thus for the time destroyed; though they seem to have stirred up a Median insurrection in the next century against Dareios II.96 However that may be, Dareios I became a zealous devotee of their creed,97 doubtless finding that a useful means of conciliating the Medes in general, who at the outset of his reign seem to have given him much trouble.98 The richest part of his dominions99 was East-Iran, which appears to have been the original home of the worship of Ahura-Mazda.100

The religion thus imposed on the Persians seems to have been imageless by reason of the simple defect of art among its cultivators;101 and to have been monotheistic only in the sense that its chief deity was supreme over all others, including even the great Evil Power, Ahriman (Angra Mainyu). Its God-group included Mithra, once the equal of Ahura-Mazda,102 and later more prominent than he;103 as well as a Goddess, Anahita, apparently of Akkadian origin. Before the period of Cyrus, the eastern part of Persia seems to have been but little civilized;104 and it was probably there that its original lack of images became an essential element in the doctrine of its priests. As we find it in history, and still more in its sacred book, the Zendavesta, which as we have it represents a late liturgical compilation,105 Mazdeism is a priest-made religion rather than the work of one Zarathustra or any one reformer; and its rejection of images, however originated, is to be counted to the credit of its priests, like the pantheism or nominal monotheism of the Mesopotamian, Brahmanic, and Egyptian religions. The original popular faith had clearly been a normal polytheism.106 For the rest, the Mazdean ethic has the usual priestly character as regards the virtue it assigns to sacrifice;107 but otherwise compares favourably with Brahmanism.

There is no reason to believe, however, that among the Persian peoples the higher view of things fared any better than elsewhere.108 The priesthood, however enlightened it may have been in its inner culture, never slackened the practice of sacrifice and ceremonial; and the worship of subordinate spirits and the propitiation of demons figured as largely in their beliefs as in any other. In time the cult of the Saviour-God Mithra came to the front very much as did that of Jesus later; and in the one case as in the other, despite ethical elements, superstition was furthered. When, still later, the recognition of Ahriman was found to endanger the monotheistic principle, an attempt seems to have been made under the Sassanian dynasty, in our own era, to save it by positing a deity who was father of both Ahura-Mazda and Angra-mainyu;109 but this last slight effort of freethinking speculation came to nothing. Social and political obstacles determined the fate of Magian as of other ancient rationalism.