The one which appears as the duality and disappears as nonduality is the invisible Soul, which is present in the form of consciousness.=

The ‘I’ hides the truth of the whole. The realization of the ultimate truth or Brahman is possible only when the seeker inquires into the nature of the ‘I’. The ‘I’ is present in the form of the mind.

The mind is present in the form of the universe, and the universe appears as waking or dream (duality) and disappears as deep sleep (nonduality).

The one that appears as the duality and disappears as nonduality is the invisible Soul, which is present in the form of consciousness.

Do not try to know who you are? By inquiring ‘Who am ‘I’, you will never reach the ultimate end of understanding. ‘Who am ‘I?’-inquiry is inadequate to realize the truth, which is beyond form, time, and space.

Try to find out what this ‘I’ is that appears and disappears. What is it that knows this appearance and disappearance of the ‘I’?

Bhagavad Gita: ~ The permanent is always there, only the transient ‘I’ comes and goes. (2.18)

That is why Ashtavakra Gita 16:10:~ If you desire liberation, but you still say 'I'. If you feel the Self is the ‘I’, you are not a wise man or a seeker. You are simply a man who suffers.

The universe is merely an illusion created out of consciousness. The water is the cause of the ice block. An ice block melts in the presence of heat and becomes one with the cause, which is the water.

In the same way, the illusory universe melts and becomes consciousness when the cause of the illusory universe is unfolded

Māyā:~

Maya, or illusion, is the most important contribution of Sage Sankara. Maya or illusion is that complex illusory power of the Atman (Soul), which is present in the form of consciousness. Consciousness is the ultimate reality or Brahman.

Ignorance is the cause of experiencing the dualistic illusion as a reality.

Maya, or the dualistic illusion, is present in the form of the mind (I). And the mind (I) is in the form of the universe. And universe appears as waking or dream (duality) and disappears as deep sleep (Nonduality).

The waking experience is real from the standpoint of the waking entity (ego). The waking experience is unreal from the standpoint of the invisible Soul, the Self.

The cause of the three states is consciousness (Brahman but consciousness itself is untouched by the profanity of illusion (Maya).

Dualistic Illusion (Maya) is temporary and is destroyed with Self-knowledge, or Brahma Gnana or Atma Gnana. :~Santthosh Kumaar