Human physical causation.

Inner chatter, unfocussed, becomes staring at externals, and reacting thereto. The line becomes blurred between the inner and the outer, and as such, the human diffuses, becoming just an amorphous outline, hue-less, in the background of existence.

Consciousness on the external, attention on the inner chatter, realization of the absolute unbridgeable distinction between the two, may eventually lead one, to realizing what the realization is.

You can wring more out of the words than Life meant to put into them, but only by intentionally aiming to do so. That pressure squeezes out energy that was not originally meant to be there, and it fuels the realization.

Waking up, and staying awake, is the intentional fueling of the realization.