Every morning, immediately after waking, just the feeling “I am” is felt. After that, witnessing of the world happens. First you witness the “I am” sensation, the feeling that you are, that you exist. This primary witnessing is the prerequisite for all subsequent witnessing. But to whom is witnessing occurring? This is what Robert and Nisargadatta ask.
It occurs to one that ever is, even without waking, to the ever present substratum.
The mystery of the worldly experience is at this point. Now you have woken up, and the witnessing of waking happens. The primary witnessing is of my own presence, my existence. The waking state, or the sense of existence, is a temporary state, alternating with the deep sleep, waking and dream states which together constitute consciousness.
So, you need to become acquainted with that witnessing substratum, the invisible, formless, intangible self that is the listener, the seer, the feeler, who itself is not of this world, but prior to it. This is That which ever is, who responds to his/her name being called when asleep, who hears the sounds of wind, rain, and thunder.