The rishis of the Vedic times who had communion with the gods gave place to the great devotees who surrendered themselves to the gods. There evolved a new literature relating to Hinduism, distinct from the Vedic literature. These are the Agamas relating to temple worship. Tamil has an immense literature of the Saiva School. The earliest religious literature in Tamil consists of devotional songs of the saints called the Alvars. They are all collected together into what is called Tiru-murai. Names of works like Nal-adiyar, Tiru-vacakam, Tevaram etc. are very famous in South India. Similarly there are the Divya-prabandhas of the Vaishnavas. These works, along with epics like Manimekhalai, all belonging to the early centuries of the Christian era, contain much of philosophy and controvert many of the Buddhistic and the Jaina doctrines. The saints were able to convert the rulers back to Hinduism from Buddhism and Jainism, but it cannot be said that the conversion was to Vedic Hinduism.
From the Brahmanas and the Upanishads, which interpret the ritualism and the philosophy of the Vedas respectively, to the works of Kumarila Bhatta and Samkaracarya it is a long leap. These two thousand years are covered on the one hand by the sutras of the Mimansa and the Vedanta, and on the other by the Epics with the Bhagavad-Gita as a part of the Mahabharata in Sanskit, and an immense literature of worship in Tamil.
This literature paved the way for the revival of Vedic religion, but it may be pointed out that the southern languages also developed a mass of literature relating to the higher aspects of non-Vedic religions. There are also Schools like Saiva-siddhanta and some sections of the Vaishnava religion that accord an independent authority to their basic texts without recognizing them as part of the Vedas. It is also interesting to note that the revival of Vedic religion was almost entirely due to the contribution of men speaking the four main Dravidian languages. Kumarila Bhatta was an Andhra, Sankaracarya came from Kerala, Ramanujacarya belonged to Tamil-land and Madhvacarya had his home in the Kannada area.
It is true that the revival was in the name of the Vedas and not in the name of the new religion of temple worship. The texts relating to the latter accepted the supremacy of the Vedas and their own literature was given a place in the religion as forming parts of the Vedas. Sankara's monism may be Upanisadic but his theology is certainly not Vedic. In the systems of Ramanuja and of Madhva, only the texts are taken from the Vedic store. The entire interpretation is based on the latter-day religion of temple worship and the Agamas.
Vishnu of the Vedas has only the name in common with the Vishnu of latter-day Hinduism, along with the attribute of the three strides (tri-vikrama). Rudra of the Veda has little resemblance to the Siva of later Hinduism, except that the name Rudra continued as synonymous with Siva. The multitude of village gods and goddesses with their various functions and legends and attributes brought about a revolution in the whole of the Vedic religion, though the new religion professed its allegiance to the Vedas.
Within the last thirty years, our knowledge of the non-Vedic elements in the evolution of Indian thought has greatly increased from the discovery of the remnants of an ancient civilization in the Indus Valley, in places known as Mohenjo Daro and Harappa. The archaeological finds in these regions reveal the existence of cities there as early as about 3000 B.C. The study of this civilization is still in its early stage and its chronological relation to Vedic civilization is still a matter of dispute. Nevertheless, valuable information regarding the civil, the social and the religious life of these people has helped to remove some of the gaps in our knowledge of ancient India.
There is no evidence of the existence of anything corresponding to Vedic ritualism in the Indus valley civilization. We, however, find many of the features of the non-Vedic civilization that contributed to the growth of later Hinduism. Thus phallus worship was a prominent feature of the religion of the Indus peoples. It represents the creative aspect of the Divine, a feature that is very indistinct in the Vedic conception of gods. Certain powers relating to the early stages of the world are attributed to the various gods in the Vedas, but God as creator is not an aspect of the Vedic texts. The Vedas speak with scorn of those; who do not perform sacrifices and those who do not make gifts. This may well be a reference to the Indus valley civilization.
Another prominent feature of the Indus valley civilization was the worship of the Mother Goddess. Various forms of the deity have been found in this region, but there is no doubt about the identity of these forms. Thus the predominance of the female aspect of the Divine in this civilization is another non-Vedic element which influenced the Indian civilization of later times. Temple worship was also prominent in this civilization. These two aspects are common to the Dravidian civilization already dealt with above. But this civilization was essentially a city civilization and it could not be otherwise in so far as the remnants are available only from the city sites. The appearance of animals and birds is another feature in this civilization that is common with the Dravidian civilization. Various figures have been discovered, but it is uncertain whether they were decorations or objects of worship. They may even form only a system of alphabet of the picture-writing type. There is much that is uncertain, but the predominance of animals is a feature that demands our attention.
Another important non-Vedic element which can be clearly discovered in the Indus valley civilization is the mode of the disposal of the dead body. Burial urns have been unearthed in the Indus valley which indicate that the dead bodies were buried and not cremated. This is distinct from the Vedic practice where dead bodies were cremated. It is interesting to speculate on the reasons for burying the dead. Is it in the hope of the soul returning to the earth, and perhaps occupying the same body that the body was not destroyed? Is this the beginning of the doctrine of transmigration? Traces of a belief in the return of the soul to the earth after death are not totally absent in the Vedic texts, but the life of the soul in a higher and happier world is the more dominant feature of the Vedic religion and not the return of the soul for another span of life in this world.
The doctrine of karman too is very faint in the early Vedic texts. The doctrine of karman is not merely a belief in the attainment of happiness as a fruit of good deeds. The essence of the doctrine is that while man in the present may be the product of his own past, he is also the sole architect of his own future. The Shraddha and various other Vedic rites show that there is a remedy in the hands of others for the evil effects of one's own actions. The doctrine of reincarnation and the doctrine of karman are interlocked and prominent in the Upanisads, but in the earlier texts they are very faint, if traceable at all. The belief that the dead person can mould his own destiny and return to this world may be at the root of not burning the dead body in this non-Vedic civilization. The idea of man being his own architect fits in better with the non-Vedic religion than with the Vedic religion of ritualism where man performs the sacrifices to propitiate gods who bestow benefits on man. The system of burying the dead bodies is based on the belief of the ability of the dead person to work out his own destiny and to return to life. The literatures of the Southern languages mention various kinds of disposal of the dead body of which one is burial of the dead body. But cremation is not unknown.
Perhaps the literary evidences are influenced by the admixture of the Vedic custom of cremation. The Sanyasa is not an institution that has developed independently from the early Vedic civilization. According to custom that has continued till today, the Sanyasis are buried after death and their bodies are not cremated. Perhaps this may be a survival of all bodies being buried instead of being cremated, and the Sanyasis, with their yogic powers, may be able to return to life and as such their bodies are not destroyed in fire through cremation.
It is doubtful whether the Indus valley civilization is distinct from the Dravidian civilization. Scholars have declared that there is great affinity between the two. It is for this reason that the Dravidian contribution to Indian thought has been discussed in detail because nearly everything said about that civilization applies to Indus valley civilization as well.