Susan Sontag, "The Aesthetics of Silence", Styles of Radical Will.
"Silence" never ceases to imply its opposite and to depend on its presence: just as there can’t be "up" without "down" or "left" without "right," so one must acknowledge a surrounding environment of sound or language in order to recognize silence. Not only does silence exist in a world full of speech and other sounds, but any given silence has its identity as a stretch of time being perforated by sound.
A genuine emptiness, a pure silence is not feasible-either conceptually or in fact. Silence remains, inescapably, a form of speech (in many instances, of complaint or indictment) and an element in a dialogue.