Any of 108 speculative texts of the
They are believed to have been composed since 500 BC, based on teachings circulated since 1000 BC. They represent the final stage in the tradition of the Vedas, and the teaching based on them is called {{link=Vedanta">Vedanta . Generally the Upanishads are concerned with the nature of reality, the individual soul ( atman ), and the universal soul ( Brahman ) and with the theory of the transmigration of souls and the nature of morality.