Duality is mere mirage created out of nondual stuff. That stuff is soul . The soul is present in the form of consciousness. Consciousness is The formless substance and witness of the three states,which comes and goes in sucssion. The three states are mere mirage created out of consciousness.
The man and world are present within the mirage. Thus whatever is felt as real within the mirage is unreal, only the substance of the mirage is real. Thus man and the world are unreal and consciousness alone is real and eternal.
Man and his experience of the world exist within the waking or dream. All the objects are present when the mind is present . And the mind is present when the universe is present. The universe is present when the waking or dream is present. The universe or the waking or the dream is nothing but Mind because without the mind they ceases to exist.
Till man thinks he and the all other objects of the world are apart from him, the duality wills persist, and there will be no unity in diversity. mind cannot exist independent of consciousness.
Thus it is necessary for the seeking mind to realize whatever exists in waking or dream is created out of consciousness , therefore, the universe(mind) as a whole is the consciousness. Thus, whatever exists within the mind is bound to be the consciousness . Thus no second thing exists other than the consciousness knowing and realizing this fact, brings unity in diversity.
Consciousness (soul) is the substance and witness of the duality. The duality is present in the form of mind. Mind is present in the form of universe. The universe appears as waking or dream and diapers as deep sleep. The one which is aware of the coming and going of the three states is neither the waking entity nor the dream entity but the formless soul, which is present in the form of consciousness. When the soul becomes aware of its formless nondual true nature in the midst of duality it is called self –awareness. It is foolish to limit the consciousness only to duality because the consciousness pervades all the three states.