From the angle of Atman(soul) as self, the three states are unreal.

It is like the sea water is forgetting its own impurities and is thinking that it is the pure water, which is a component of the sea water. By such thinking, the impurities are not filtered and the saltiness does not disappear. To remove the impurities, work (filtration) should be done. Then the sea water can really become the pure water. Thinking is not work. Filtration is the work.

 From the angle of Atman(soul) as self, the three states are unreal.  The man and the world are reality within the waking. The mind or I appear as waking and dream, and disappear as deep sleep.  The one which is aware of the three states is within the three states, and it is apart from the three states. it is within the three states   as  their formless substance, and it is without the three states as their  formless witness.  It is apart from the three states because it is not an entity or identity within the waking or dream.  The three states are mere object to the soul or consciousness, the innermost self.

Oneness is possible only when we become aware of the fact that, the formless soul  is the true self, and able to view and judge the three states , on the standpoint of formless soul  as self.  The diversity (duality/illusion) is reality, only on the base of  the ego or waking entity as self.

Therefore it is necessary to discover and realize the fact that, the source of the three states is soul, and soul is the true self, and witness of the three states, which appear and disappear in succession.  The three states are unreal, on the standpoint of the formless soul as self; this helps the seeker to realize the fact that the world is unreal.

 The world is reality only within the waking experience, but waking is as real as dream.  Therefore the substance and witness of the three states, which is soul or consciousness is the true self, and real. And the formless   soul itself is ultimate truth or Brahman.