The questions which Upanishadic thinkers wanted to answer were the following:
(1) They wanted to know about life after death.
(2) They wanted to know why sacrifices should be performed.
(3) They believed that there were something permanent in the universe that would last even after death. They described this as 'atman' or 'individual soul 'and the 'brahman' or the 'universal soul'.
(4) They believed that ultimately both the atman and the brahman were one.
