Waking experience also as unreal as dream.

 Deeper self-search reveals:-

The dream or Waking experiences are absent, in deep sleep.  The witness can remain with or without the dream or waking experiences.

The deep sleep experience proves that the witness can remain without the experience of duality.  Therefore, one can come to firm conclusion to get the conviction that the witness is formless and apart.

One  has to hold on to the formless  witness, which is the soul, as Self and  learn to view and judge the three states  on the base of soul as self,  to realize the fact that  Waking experience also as unreal as dream.