In all religions, when they have reached a certain stage of development, the impulse arises to find the unity of the divine being among the multifarious crowd of deities. On the Ganges the Brahmans or priests attained to this unity by elevating the power of the holy acts which controlled the deities, and was mightier than they, into the lord of the gods, by uniting with this conception the great breath or world-soul, the source of life springing up in nature. In Iran the reform did not look on nature as one, like the Brahmans on the Ganges, and owing to the character of the land and the strong contrasts there met with it could not easily perceive in it any single whole; on the contrary, it comprehended in unity, on the one hand, the good beneficent side of nature, which gives increase, light, and life to men; and, on the other, ranged the harmful powers together in opposition to the good. Hence it came about that the spirits which worked on either side were, so to speak, combined, and the two totals came forward in opposition. To these totals the reform sought to give unity by placing a chieftain at the head of each, the good and the bad. The chief of the good was Ahura, _i.e._ the lord, who is also denoted by the name Mazda, _i.e._ the wise, but he is generally invoked by the united title Ahura Mazda (Auramazda in the dialect of Western Iran), the wise lord; occasionally, in the Avesta, he is called Çpentomainyu, _i.e._ the spirit of holy mind, the holy spirit. In the Rigveda the name Ahura Mazda, in the form Asura Medha, is used for more than one god of light. The chief of the evil spirits was Angromainyu, _i.e._ he that thinks evil, the destroying spirit.