1. A prose passage from the Prashna Upanishad explains the meaning of the word “AUM”.
If man meditates on the first letter “A” then he attains to knowledge. This is the world of Riks. Here he experiences the greatness of the spirit.
If man meditates on the second letter “U” he is led to the middle world of the Soma by the Yajus and such a man is accomplished in mind. Here he experiences the majesty of the spirit.
If man meditates on the third letter “M” he reaches the highest Purusha and is perfected in the light that is the Sun. As a snake puts off his skin so will man be relieved from sin and evil. This is the world of Samans.
The man who utters “AUM” is led to the inner,outer and middle action of the spirit. The man who possesses the knowledge of AUM is led to the supreme spirit which is calm, ageless, fearless and immortal.
2. The symbols described above in the passage of the Prashna Upanishad are obscure to our intelligence but represent a psychical experience leading to different states of spiritual realisation. Later in Mandukya Upanishad these symbols are cast aside and the true significance of these three letters is brought forth before us.
3. Our modern thought is returning to the knowledge that behind the operations of our outward physical consciousness are other operations that are subliminal of which our waking mind is the surface action.