The primitive, base of this religion is difficult to discern clearly: but we may recognise in it most of those beings or personifications of natural phenomena which were the chief objects of worship among all the ancient nations of Western Asia--the stars, Sirius, the moon, the sun, water and fire, plants, animals beneficial to mankind, such as the cow and the dog, good and evil spirits everywhere present, and beneficent or malevolent souls of mortal men, but all systematised, graduated, and reduced to sacerdotal principles, according to the prescriptions of a powerful priesthood. Families consecrated to the service of the altar had ended, as among the Hebrews, by separating themselves from the rest of the nation and forming a special tribe, that of the Magi, which was the last to enter into the composition of the nation in historic times. All the Magi were not necessarily devoted to the service of religion, but all who did so devote themselves sprang from the Magian tribe; the Avesta, in its oldest form, was the sacred book of the Magi, as well as that of the priests who handed down their religious tradition under the various dynasties, native or foreign, who bore rule over Iran. The Creator was described as "the whole circle of the heavens," "the most steadfast among the gods," for "he clothes himself with the solid vault of the firmament as his raiment," "the most beautiful, the most intelligent, he whose members are most harmoniously proportioned; his body was the light and the sovereign glory, the sun and the moon were his eyes." The theologians had gradually spiritualised the conception of this deity without absolutely disconnecting him from the material universe. [Illustration: 012.jpg THE AHURA-MAZDA OF THE BAS-RELIEFS OF PERSEPOLIS] Drawn by Faucher-Gudin, from Flandin and Coste. He remained under ordinary circumstances invisible to mortal eyes, and he could conceal his identity even from the highest gods, but he occasionally manifested himself in human form. He borrowed in such case from Assyria the symbol of Assur, and the sculptors depict him with the upper part of his body rising above that winged disk which is carved in a hovering attitude on the pediments of Assyrian monuments or stelae. [Illustration: 012b.jpg HYPOSTYLE OF HALL OF XERXES: DETAIL OF ENTABLATURE] In later days he was portrayed under the form of a king of imposing stature and majestic mien, who revealed himself from time to time to the princes of Iran.* * In a passage of Philo of Byblos the god is described as having the head of a falcon or an eagle, perhaps by confusion with one of the genii represented on the walls of the palaces. [Illustration: 013.jpg AN IRANIAN GENIUS IN FORM OF A WINGED BULL] Drawn by Boudier, from a photograph. He was named Ahuro-mazdao or Ahura-mazda, the omniscient lord,* _Spento-mainyus_, the spirit of good, _Mainyus-spenishto_** the most beneficent of spirits.