The waking experience [mind or `I'] is a created and sustained by Ataman. Ataman is the essence which pervades the whole experience of diversity. Without Ataman [consciousness] the waking or dream is dead Material [matter].
When Atman [consciousness] remains in its formless true nature there is no individuality, no World and no God or any sort of experience. Ataman can only be conscious of objects when it has manifested in a physical form within the illusion. Ataman [Consciousness] is latent in everything in the waking experience [mind] as its formless substance and witness, in all the three states - it is universal, non-personal, and all-pervading.
Everything within n the three states is Ataman, and that is what we all are and also the world, presently. Ataman becomes ignorant of its formless nature within the illusion. When waking or dream disappears then "it merges with the Ataman. This is all a process of happening. Becoming dual and nondual is the nature of Ataman. Thus, duality and non duality is the play of Ataman. The duality is reality only in ignorance. In reality there is neither duality nor non duality everything is one and absolute.
Therefore the individual experience of birth, life and death are reality only on the base of physical self or `I'. And it is becomes a greatest obstacle if one seeks truth on the false physical identity within the false experience. Therefore, the seeker of truth has to consider the whole waking experience as illusion in order to acquire nondual wisdom.