According to Indian tradition, the worship of Vishnu is of immemorial antiquity. Vishnu is mentioned in the Vedas. Western scholars find a gradual evolution of the Vishnu cult from the Vedas downwards, while orthodox opinion holds that Vaishnavism is well expounded in the Vedic scriptures. It is argued by European and American students of our ancient texts that Vishnu is a minor god in the Vedic pantheon, less important than Indra or Varuna and associated with the Adityas. They seem to ignore a well-known Vedic declaration that Vishnu is the greatest and Agni the least among the gods. The Katha Upanishad identifies final release with attaining the world of Vishnu. It is supposed that Vishnu gained the importance by becoming the protector of sacrifices and that later Bhaga, Bhagavan, Narayana and Vasudeva became amalgamated with him in course of time.
Later still, Krishna is held to have been identified with Vasudeva. The Bhagavatas, a sect of worshippers of Bhagavat (Bhagavan), are said to have swelled the number of Vaishnavas. It is well-known that the epics celebrate the incarnations of Vishnu as Rama and Krishna. The Puranas elaborate the other incarnations. The prominent place occupied by Vishnu in the epics and the Puranas has been regarded as both the cause and the result of the popularity of the cult. Another factor to be taken into consideration is the contribution of texts of semi-scriptural validity known as the Agamas. Works of this kind are available glorifying Vishnu, Siva and Sakti.
The Vaishnava Agamas form the basis of the worship of Vishnu in temples. They prescribe how the idols are to be made, how temples are to be constructed, how the daily worship and festivals are to be conducted and so on. It should also be noted that they lay down rules for carrying on domestic worship also and that the religious life of the Hindus is today largely governed by the Agamas of the three sects. The Vaishnava Agamas belong to two slightly different schools of thought and practice-the Vaikhanasa and the Pancharatra. The former uses Vedic mantras to a greater degree and its followers are confined to a small hereditary caste. The Pancharatra has no such restriction.