Very little is known as to the religion of the Parthians. It seems probable that during the Persian period they submitted to the Zoroastrian system, which was generally maintained by the Achaemenian kings, acquiescing, like the great bulk of the conquered nations, in the religious views of their conquerors; but as this was not their own religion, we may conclude that they were at no time very zealous followers of the Bactrian prophet, and that as age succeeded age they became continually more lukewarm in their feelings, and more lax in their religious practice. The essence of Zoroastrian belief was dualism--recognition of Ormazd as the great Principle of Good, and of Ahriman as the Principle of Evil. We need not doubt that, in word, the Parthians from first to last admitted this antagonism, and professed a belief in Ormazd as the supreme god, and a dread of Ahriman and his ministers. But practically, their religious aspirations rested, not on these dim abstractions, but on beings whose existence they could better realize, and whom they could feel to be less remote from themselves. The actual devotion of the Parthians was offered to the Sun and Moon, to deities who were supposed to preside over the royal house, and to ancestral idols which each family possessed, and conveyed with it from place to place with every change of habitation. The Sun was saluted at his rising, was worshipped in temples, under the name of Mithra, with sacrifices and offerings; had statues erected in his honor, and was usually associated with the lesser luminary. The deities of the royal house were probably either genii, ministers of Ormazd, to whom was committed the special protection of the monarchs and their families, like the _bagaha vithiya_ of the Persians, or else the ancestors of the reigning monarch, to whom a qualified divinity seems to have been assigned in the later times of the empire. The Parthians kings usually swore by these deities on solemn occasions; and other members of the royal family made use of the same oath. The main worship, however, of the great mass of the people, even when they were of the royal stock, was concentrated upon ancestral images, which had a place sacred to them in each house, and received the constant adoration of the household.