The core of the Aryans' religion was its focus on sacrifice. By giving valued things to the gods, people strengthened them and established relationships with them. As in anceint Persia, the god of fire was particularly important. Agni, the Aryan fire-god, ahd three forms: fire, lightning, and the sun. In his capacity as the sacrificial fire of the priests, he served as a liaison between human beings and the gods, carrying to the gods the offerings made by the Brahamn priests. The fire sacrifice was the most elaborate of the sacrifices, but all the Aryan gods enjoyed having offerings made to them. Under the priestly monopoly of the Brahmans, correct sacrifice and proper ritual became so important that most Brahmans believed that a properly performed ritual would force a god to grant a worshiper's wish.
These Brahmanic thinkers also developed ideas about the nature of the cosmos. Ancient Indian cosmology focused not on a creator who made the universe out of nothing, but rather on endlessly repeating cycles. Key ideas were samsara, the transmigration of souls by a continual process of rebirth, and karma, the tally of good and bad deeds that determined the status of an individual's next life. Good deeds led to better future lives, evil deeds to worse future lives-even to reincarnation as an animal. Gradually arose the concept of a wheel of life that included human beings, animals, and even gods. Reward and punishment worked automatically; there was no all-knowing god who judged people and could be petitioned to forgive sin, and each individual was responsible for his or her own destiny in a just and impartial world.
To most people, ecpecially those on the low end of the economic and social scale, these concepts were attractive. All existence, no matter how harsh and bitter, could lead to better things. By living righteously and doing good deeds, people could improve their lot in the next life. There was another side to these ideas: the wheel of life could be seen as a treadmill, giving rise to a wanting for release from the relentless cycle of birth and death. One solution offered in the Upanishads was moksha, or release from the wheel of life. Brahmanic mystics claimed that life in the world was actually an illusion and that the only way to escape the wheel of life was to realize that the ultimate reality was unchanging.
This unchanging, ultimate reality was called brahman. The multitude of things in the world were all fleeting; the only true reality was brahman. Even the individual soul or self, atman, is ultimately the same substance as teh universal brahman, in the same way that each spark is in substance the same as a large fire. Equating the individual self with the ultimate reality suggested that the apparent duality in the world is in some sense unreal. At the same time it conveyed that all people had in themselves an eternal truth, which corresponded to an identical reality.
The Upanishads gave the Brahmans a high status to which the poor and lowly could aspire in a future life. The Brahmans greeted the concepts and those who taught them with tolerance and understanding and made a place for them in traditional religious practice. The rulers of Indian society also encouraged new trends, since the doctrines of samsara and karma encouraged the poor and oppressed to labor peacfully adn dutifully. In other words, although the new doctrines were intellectually revolutionary, in social and political terms they supported the existing power structure.