Mind [waking experience] is the manifestation of the Atman, which is in the form of consciousness. Neither Atman can be separated from the mind [waking] nor the mind be separated from the Atman. Only one has to overcome the ignorance stop viewing and judging the worldview on the base of physical self and view and judge the worldview on the base of Atman as self in order to realize the mind[waking] is mere mirage created out of Atman and there is nothing exist other then Atman.
The witnessing happens, only when one learns to view and judge the worldview on the base of Atman. If one thinks the physical body or the `I' as witness, he will not be able to assimilate the self-knowledge. The witness is always apart in illusion. When ignorance disappears then the illusion also disappears. When there is no illusion then there is neither the witness, nor the witnessed, everything is one and prevails as Atman.
Atman is sentient and waking experience is insentient. Without the sentient the insentient is non-existent. The sentient is independent whereas the insentient is dependent.