The illusion is present in the form of ‘I’ or mind.

The experiencing birth, life, death and the world are within the illusion.  Due to ignorance, the illusion is experienced as reality. The illusion is present in the form of ‘I’ or mind. Mind is present in the form of universe. Universe appears as waking or dream and disappears as deep sleep.   The three states are one in essence and that essence is consciousness. The consciousness (soul) is the innermost self. On the standpoint of the innermost self the three states are illusory.

Thus experiencing the birth, life, death and the world within the illusion (waking or universe) with the illusory self (waking entity or ego), within the illusory experience (waking), has to be illusion.

The illusion is created, and sustained, and finally dissolves as consciousness, which is the innermost Self.  Since, there is no second thing other than the consciousness (soul); the consciousness itself is ultimate truth or Brahman.   The one who has realized this truth for him this illusion is passing show because he is fully aware of the fact that his body, his ego and his experience of the world to be consciousness. Practical peoples approach is more practical, and they are stuck with the reality of the practical life within the practical world, they take it as real whereas Gnani sees   his body his ego and his experience of the world as consciousness.  

Realizing the difference between the seen (duality or waking or dream) and the formless witness(soul), when the soul gets disunited from `seen (duality or waking or dream) and established in identity with it self, which is the formless soul. The soul  is present in the form of consciousness  one is said to have known liberation from duality.  

While dreaming one is being reminded his waking state, he comes to recognize the dream, therefore, he wake up. Immediately he realizes that waking is the only means of escape from the woes of the dream state.

Even so the seeker of truth following the path of self-Knowledge or Brahma Gnana or Atma Gnana, while perceiving the difference between the Seen (duality or waking or dream) and the Formless Witness (soul), comes to realize the apparent connection with the Seen was due to mistaken identity.

The seeker is able to reestablish the real connection and recognizes real identity (soul). – The Truth, Consciousness and Bliss solidified. Such a seeker is said to have come to know his /her liberation from duality. The moment this truth is realized, the entire realm of objective reality becomes unreality along with ignorance and Truth -Realization takes place immediately.