define atman-brahman
Atman is that which makes the other organs and faculties function and for which indeed they function; it also underlies all the activities of a person, as brahman (the Absolute) underlies the workings of the universe. Atman is part of the universal brahman, with which it can commune or even fuse. So fundamental was the atman deemed to be that certain circles identified it with brahman. Of the various systems (darshans) of Hindu thought, Vedanta is the one that is particularly concerned with the atman.