The Vishnuism and Sivaism of the south go back to the early centuries of our era, but the chronology is difficult.  In both there is a line of poet-saints followed by philosophers and teachers and in both a considerable collection of Tamil hymns esteemed as equivalent to the Veda.  Perhaps Sivaism was dominant first and Vishnuism somewhat later but at no epoch did either extinguish the other.  It was the object of Sankara to bring these valuable but dangerous forces, as well as much Buddhist doctrine and practice, into harmony with Brahmanism.

Islam first entered India in 712 but it was some time before it passed beyond the frontier provinces and for many centuries it was too hostile and aggressive to invite imitation, but the spectacle of a strong community pledged to the worship of a single personal God produced an effect.  In the period extending from the eighth to the twelfth centuries, in which Buddhism practically disappeared and Islam came to the front as a formidable though not irresistible antagonist, the dominant form of Hinduism was that which finds expression in the older Puranas, in the temples of Orissa and Khajarao and the Kailasa at Ellora.  It is the worship of one god, either Siva or Vishnu, but a monotheism adorned with a luxuriant mythology and delighting in the manifold shapes which the one deity assumes.  It freely used the terminology of the Sankhya but the first place in philosophy belonged to the severe pantheism of Sankara which, in contrast to this riotous exuberance of legend and sculpture, sees the highest truth in one Being to whom no epithets can be applied.

In the next epoch, say the twelfth to the seventeenth centuries, Indian thought clearly hankers after theism in the western sense and yet never completely acquiesces in it.  Mythology, if still rampant according to our taste, at least becomes subsidiary and more detachable from the supreme deity, and this deity, if less anthropomorphic than Allah or Jehovah, is still a being who loves and helps souls, and these souls are explained in varying formulae as being identical with him and yet distinct.

It can hardly be by chance that as the Hindus became more familiar with Islam their sects grew more definite in doctrine and organization especially among the Vishnuites who showed a greater disposition to form sects than the Sivaites, partly because the incarnations of Vishnu offer an obvious ground for diversity.  About 1100 A.D.[27] the first great Vaishnava sect was founded by Ramanuja.  He was a native of the Madras country and claimed to be the spiritual descendant of the early Tamil saints.  In doctrine he expressly accepted the views of the ancient Bhagavatas, which had been condemned by Sankara, and he affirmed the existence of one personal deity commonly spoken of as Narayana or Vasudeva.