"In the Vedas as well as in the older portions of the Zind-Avesta (see the Gathas), there are sufficient traces to be discovered that the Zoroastrian religion arose out of a vital struggle against a form which the Brahminical religion had assumed at a certain early period.‘ ... “These facts throw some light upon the age in which that great religious struggle took place, the consequence of which was the entire separation of the Ancient Iranians from the Brahmans and the foundation of the Zoroastrian religion. It must have occurred at the time when Indra was the chief god of the Brahmans."