Self is not ‘you’ but the self is that witnesses ‘you and the world’ together without the physical apparatus. You are the false self(ego or waking entity) within the false experience(waking) bound by birth, life and death and form, time and space whereas the ‘Self ‘ is birthless and deathless because it is formless. Thus self is not limited to waking state alone because it pervades in everything and everywhere in all the three states. Thus limiting the ‘self’ to waking entity alone is cause of the ignorance.
The dream entity (you) and the dream world becomes falsehood when waking takes place. Similarly the waking entity (you) and the waking world become falsehood when wisdom dawns. Wisdom dawns when waking entity (you) realizes it itself is not the self but the self is that which witnesses the coming and going of the three states. The witness and the three states are one in essence. That essence is consciousness (Atman). Thus consciousness is ultimate truth or Brahman. Atman is second to none.
Thus one has to know ‘What is mind? ‘What is the substance of the mind?’ and ‘What is the source of the mind?’ in order to realize the non-dualistic or Advaitic truth.
The ultimate truth is one without the second, the one is not in the sense half or two, but the one that remain forever One, without the second. The consciousness is all pervading. There is no place where consciousness is not.
Consciousness is in everyone, consciousness is in everything .consciousness is one behind many. Consciousness alone is. It means the universe and its contents are the visible form of consciousness. And consciousness in turn is invisible form of the universe, which appears as mind.
That is why Sage Sri, Sankara says in commentary in Vedanta sutra that what is accepted without proper enquiry will not lead a person to the final goal. On the contrary, such acceptance will result only in evil, in something which is detrimental to our spiritual progress. Seeker of truth should not believe blindly in traditional orthodox nonduality without verifying all the facts from every angle. One has to reflect through reasoning over and over again without getting tired of the process.
Everything is made of the same substance, whether it be inside--as in dreams--or outside as in waking. Whatever is seen as object, heard as sound or name is of the same substance. Many have begun to suspect this truth. This is the great lesson to be learnt. Consciousness is all this."
Reason should not be interpreted to mean intellect. Reason is that which finally distinguishes between real and unreal, false and true, and therefore it takes all the three states into account.