What is that becomes waking? What is it that becomes dream? What is that becomes deep sleep

Chandogya Upanishad:-
 

"When a person is sleeping soundly, free from dreams, with a still mind, that is the Self, fearless and deathless. That is Brahman, the supreme."


One has to find answers for: - What is that becomes waking? What is it that becomes dream? What is that becomes deep sleep. As one goes in deeper self-search he becomes aware of the fact that the consciousness alone is the cause of the three states and it itself is uncaused. Until one thinks the self is limited to an individual and it is within the heart he will never be able to come out of physicality. The self is not an individual because it pervades in all the three states and it is formless substance and witness of the here states. The individual experiences of birth, life, death and the world are nothing to do with the self because the self is birth -less and deathless. The form, time and space are nothing to do with the self, because it is formless, timeless and space less existence. Thus judging the truth on the bases of form, time and space is erroneous. Thus ‘I’ or ‘I AM’, which is limited to physicality, will yield only half truth.

That is why Sri, Sankara says in VivekaChudamani :-

63. Without causing the objective universe to vanish and without knowing the truth of the Self how is one to achieve Liberation by the mere utterance of the word Brahman? — It would result merely in an effort of speech.


65. As a treasure hidden underground requires (for its extraction) competent instruction, excavation, the removal of stones and other such things lying above it and (finally) grasping, but never comes out by being (merely) called out by name, so the transparent Truth of the self, which is hidden by Maya and its effects, is to be attained through the instructions of a knower of Brahman, followed by reflection, meditation and so forth, but not through perverted arguments.

-FORMLESS PATH