Abheda literally means non-difference or without difference. It is a near synonym for the concepts denoted by the English words ‘identity’, ‘non-dualism’, ‘monism’. It is an important term in Advaita, the non-dualist philosophy.
Abheda, non-difference of self and Brahman, and non-difference of Brahman and the world of multiplicity, are foundational concepts of the school of Advaita Vedanta, beginning with Gaudapada in the 7th century and established by Adi Shankaracharya in the 9th century CE. According to Gaudapada, “That the ananyatvam (identity) of jiva and atman without any abhedana (difference) is praised and diversity is censured – that is rational only (on this view).” (Karikas III.14). In his Karikas, the texts of Upanishads are divided into sayings that emphasize the absence of bheda (difference) and those of lesser significance that stress difference.
Adi Shankaracharya, in his Brahmasutra Bhashya, called his own system abheda darshana. If, for Advaita Vedanta, the self is ultimately non-dual and without difference, a complex dialectic must be employed to exclude all notions of difference and multiplicity. These invalid notions are produced by maya, and are obstructive of true vision of the non-dual self. To assert non-difference, Vedanta employed the epistemological distinction between two levels of truth, the absolute and the relative. Thus, Adi Shankaracharya, using ananyatvam as a synonym for abheda, states – that distinction (between the enjoyer and the enjoyed) does not exist because there is understood to be non-difference of cause and effect. The effect is this manifold world consisting of akasha, space, and so on; the cause is the highest Brahman.” (Brahmasutra Bhashya II.1.14) Absolute truth discerns non-difference, relative truth discerns difference, that is, the multiplicity of apparent reality. As Mandana Mishra states – Non-difference alone is ultimately real, and difference is imagined because of beginningless avidya having non-difference as the basis of reference of the imagination. (Brahma Siddhi II.12).