The Inquiry and Reasoning reveals:-
The witness is the Soul, which is in the form of consciousness. Without the Soul or consciousness the three states cease to exist. Therefore, Soul or consciousness itself is the formless substance and witness of the three states.
On the standpoint of Soul/Spirit, the three states are non-existent. Since Soul is formless and non-dual in its nature. In waking and dream the self becomes ignorant of its own non-dual nature and it experiences the duality as reality.
The fact that ‘Self’ is not the physical and analyzing the three states on the base of physical self creates the ignorance and leads the seeker towards imagination or intellectuality. Intellectuality is mere speculation derived on the base of physical self.