This country was situated in an upper valley of the Oxus, formed by the Hissar mountains on the north, and at the south the Hindu-Kush, extending from the Pamir plateau on the east to the great desert of Chorasmin on the west, a fruitful valley, well watered, affording on the hill slopes of the southern range favorable pasturage for flocks and herds. From this region the Iranian branch finally spread westward and southerly throughout the lands later known as Iran or Persia. It has been suggested that the separation of the Indo-Iranians was the result of religious differences. The schism indicated in the Rig Vedas and Avesta seems to have grown out of the distinction which finally arose between the signification of the words “Asura” or “Ahura,” as applied to Deity. The earlier faith of these people seems to have been a pure nature worship, the sun, the sky, light, fire, the elements, throughout which appears also a spiritual conception of a Supreme Being, Lord of the Sky, the Sun, Creator of all things, who was known as “Asura,” or “Ahura.” The most ancient signification of this word is “The Broad and Enfolding,” its earliest application as Lord of the Sky, is, perhaps, a reminiscence of that remote period in the history of these people when they roamed the vast steppes of northern central Asia. In the spiritual conception which grew from this, Asura became the Lord of the Broad Heavens, the God of Light, the Infinite. The word Deva, from the Sanskrit Div, signified “brilliant,” “shining.” In its spiritual sense, the “Shining Ones” applied originally to the ministering spirits, the bright messengers of Asura. From the word Deva, we have the word Deus, God; Divus, divine; dæmons, and other similar forms in various branches of Aryan speech. At first, Asura is the most sacred name used for Deity. Later on, with the increase of gods in the Hindu pantheon, the term Asura is conferred as a highest dignity upon the greater gods, as Asura-Varuna, Asura-Indra. There came a time, however, as appears in the Vedas, when the Asuras signified a class of spirits inferior to the Devas, and finally as spirits opposed to the gods. As the Asuras were degraded, the Devas were exalted. With the Iranian branch, there was no such change. The ancient “Asura,” in Persian, “Ahura,” remained from first to last their great divine One; nor throughout the whole history of Persian mythology are there “any gods before” him. The word Dævas, with them came to signify evil spirits—devils. That a schism arose, is apparent; and also that it was local. “Hard by the believers in Ahura,” says Zoroaster, “dwell the worshippers of the dævas.” Such were the conditions when the great prophet and sage appears upon the scene, not as the apostle of a new religion; but as a teacher of the higher meanings of their ancient faith.