The word ‘atman’ is derived from ‘an’ – to breathe. It is the breath of life – atma te vatah (Rig Veda VII 87.2).
Gradually its meaning is extended to cover life, soul, self or essential being of the individual. Shankaracharya derives atman from the root which means ‘to obtain’ ‘to eat or enjoy or pervade all.’
Atman is the principle of man’s life, the soul that pervades his being, his breath (prana), his intellect (prajna), and transcends them.
Atman is what remains when everything that is not the self is eliminated.
The Rig Veda speaks of the unborn part ‘ajo bhagh’ (Rig Veda X 16. 4) – There is an unborn and so immortal element in man which is not to be confused with body, life, mind and intellect. These are not the self but its forms, its external expressions.
Our true self is pure existence, self-aware, unconditioned by the forms of mind and intellect. When we cast the self free from all outward events, there arises from the inward depths an experience, secret and wonderful strange and great. It is the miracle of self knowledge – atma jnana.
Just as in relation to the universe, the real is Brahman, while name and form are only a play of manifestation, so also the individual egos are the varied expressions of the One Universal Self.
As Brahman is the eternal quiet underneath the drive and activity of the universe, so Atman is the foundational reality underlying the conscious powers of the individual, the inward ground of the human soul.
There is an ultimate depth to our life below the plane of thinking and striving. The Atman is the super reality of the ‘jiva,’ the individual ego.
Dr S Radhakrishnan
(Source: The Principal Upanishads by