Silence, regarded metaphysically, is considerably different from conventional silence, dualistically defined, silence as one element in a comparison of opposites, silence as the opposite and complement of noise. The silence which the Maharshi states is more powerful than speech, a more potent medium of instruction than words, the silence in which, and by which, occurs the transmission of mind via mind in which the ultimate doctrine of the Buddha was handed down from patriarch to patriarch according to the Ch'an Masters, is rather the background of the time-illusion, the interval between thoughts that is normally imperceptible to divided mind, of infinitesimal duration, but which is in itself intemporal, of no, or of infinite duration. If we can seize it, so we are told, and hold it, the mind stays open, and we are awake at last.
What, then, is it - this metaphysical silence? Clearly it is the 'Buddha-mind' of Ch'an, the 'Witness' of Vedanta, the 'Father' of Christianity, i.e. whole-mind. The mechanism of dualism seems to be that of the escapement of a clock, which is also an instrument for recording time. One half momentarily stops the flow of time, and then the other, tic-toc, tic-toc. So does each half of split-mind, tic-toc, tic-toc, and the interval between each tick is pure movement, the background, the intemporal reality which, measured by each alternative tick, becomes time as we know it. And the tic-toc, the alternative stoppage, is the comparison of opposites, the activity of split-mind, which we know as thought and mentation.
We can now see why every one of the awakened tells us ad nauseam that all we need to do is to arrest the movement of thought in order to know whole-mind and find ourselves awake. It explains also why wu or satori is always precipitated by a sudden sound, anything from a clap of thunder to the snapping of a twig, or, indeed, any other sensory perception whatever. Such perception momentarily arrests the eternal tic-toc of thought and, the subject being ripe, whole-mind takes possession and is no longer split.
That the awakened continue to know divided mind, in communicating with those who remain identified, is evident, but for them that condition is the abnormal, and the state of whole-mind the normal, instead of the contrary as with the rest of us. But it is surely an error to suppose that we do not know whole-mind in our daily life - for the consciousness that is aware of our having thought is certainly that, a consciousness that is ever awake, is always present, and that alone is 'real'.