1 What experiences the dream when the Waking experience is totally absent?
2 When ‘Self’ is not the physical, what is it that witnesses the three states in succession?
When ‘Mind’ subsides then the waking or dream experience also subsidies and whatever prevails without the waking or dream is identified as deep sleep. Therefore, the waking or dream is mere mental experience and they subside and become one with the source from where they have erupted from.
Until and unless one becomes aware of the fact that, the waking or dream rises and subsides from this formless source, which is the soul, he is bound to prevail in illusion experiencing it as reality. And he will continue to view and judge the worldview on the base of waking entity or physical self (ego).
When one realizes the formless substance and witness is the soul,which is present in the form of consciousness and and the soul is the true self then he will realize the fact that, the duality or diversity is mere mirage. And there is no second thing other then soul, which is in the form of consciousness. That is second less existence.
One has to come to firm conviction that the soul or consciousness itself is the formless substance and witness of the three states, in order to realize the fact that, experience of diversity is mere illusion. There is no division in the soul or consciousness in its true nature.
On the standpoint of the soul as self, the physical body, world, and concept of God and religious affiliations are nonexistent. Take the illustration of Deep Sleep. The nature of the soul, the innermost self is like deep sleep. Thus, remembering the nature of soul, the innermost self like deep sleep experience, where there is no scope for duality. Therefore, the nature of the soul/self is non-dual without the beginning and end. Thus, the whole experience of duality is rises, sustained and subsides in soul. The formless substance and witness of the three states is the soul. Realizing the soul as self is “Self-Realization”.