This Great Teaching occurs in the Aitareya Upanishad. It is known as the swaroopa vakya, because it indicates the swaroopa or true nature of the Ultimate Reality. Brahman in this teaching means Truth, or Reality, or God or whatever we may choose to call it. The verse states “Whatever exists here, whether moving or unmoving, all is supported by Consciousness. The basis (of the universe) is Consciousness. Consciousness is Brahman.”
Brahman is the one Consciousness in all manifested forms. As gold remains gold alone, whether it is molded into coins, jewellery, idols or anything else, the universal Consciousness remains the same, no matter in which form it is manifested. Whatever we see or know as this universe, as God and as ourselves, is nothing but the play of this one Consciousness. It is the light of Consciousness that illumines everything, both within and without. Sankara retells a story from the Upanishads, which is actually a dialogue between a guru and his disciple.
The guru asks the disciple, by what light do you see? The disciple replies, by sunlight in the daytime, and by lamplight at night.
G: By what light do you see these lights?
D: By the light of my eyes, naturally.
(Without the eyes, all other lights prove useless for the purpose.)
G: And by what light do your eyes see?
D: By the light of consciousness, indeed!
(Even when the eyes are open, one can miss seeing an object right before one’s eyes if the
awareness is directed elsewhere.)
G: That is true!
Thus, know that Consciousness is the Light by which all else is seen.
Prajnanam Brahma means, Consciousness is the Reality, Consciousness is All. For the spiritual seeker, perhaps it may be easier to start from the opposite direction. In the beginning, one can meditate on the truth that All is Consciousness. Whatever we perceive through the senses, whatever we understand through the mind, all that we are aware of in the outer world and in the inner world – all these are manifestations of the one Consciousness. When we are in tune with this truth, we can meditate on the ultimate truth that Consciousness is All. Consciousness is all there is! All names, forms and qualities are nothing but superimpositions on Brahman, the unchanging Consciousness. Consciousness alone exists as All.