Between the 7th and 5th centuries B.C.E., the early texts of the Upanishads were composed. They are the last texts of the Vedas and are known as the Vedanta or Conclusion of the Vedas. The tone of these treatises and poems is philosophical and mystical, and there is no longer an interest in ritual sacrifice.

While the Vedas were hymns to the outer world of creation, to nature and its forces, the Upanishads provide a transformation of thought, in which the Divine or transcending principle is searched for from within. The self-training for this is yoga.

The Upanishads, like the Vedas, were not written down to begin with, but memorized and handed down from teacher to pupil. The Sanskrit term Upanishad refers to sitting for instruction at the feet of a master, and the Sanskrit word guru means a spiritual teacher. This method of transferring knowledge by teaching yoga on a one-to-one basis has been employed up to the present day. However, increased communication and translation of the texts are no changing this approach.

The teaching of the Upanishads was concerned with the desire for release (moksha) from the round of births and deaths through reincarnation that had been accepted as a concept by the time of the Upanishads’ conception. This release, the writings taught, was to be gained through meditation, yoga, and asceticism, which would unite the soul (atman) within with the absolute spirit (brahman) without.

The concept of karma, by which every action, good or bad, has a cause and therefore a reaction that is impossible to escape, was also accepted. Because of their reincarnation, it is believed, actions in our present lives determine our fate in lives that follow through the karmic memory in our higher consciousness. Desire is the cause of karma and, because of the desire to live in the ordinary world, the cycle of samsara, the endless chain of rebirth, cannot be escaped. Actions without desires for reward or attainment free the soul from the effects of karma.

The thoughts contained in the Upanishads, counteracting the ritualism of the Vedas, were enormously influential. By 500 B.C.E., religion and society were changing. Cities had begun to grown again, and a strong merchant class was upsetting the old orders of priest, warrior, trader, and serf. The Vedic-Aryans had taken over northern India, and the center of their culture was in the north-eastern delta of the Ganges.

An aggressive empire of the Maghada dynasty led a number of disaffected groups to follow their own paths of beliefs away from the increasingly rigid interpretation of the Brahmin priests. Breakaway sects of ascentics, mystics, and renuciants began to follow new teachers, such as Siddartha Gautoma (c.563 - 483 B.C.E.), the Buddha, and Vardhamana (c. 599-527 B.C.E.), who became the Mahavira and founded Jainism.