"Sontag seems correct to me when she concludes the essay by reminding us that "In the strictest sense, all the contents of consciousness are ineffable," that "Every work of art, therefore, needs to be understood not only as something rendered, but also as a certain handling of the ineffable."
In the greatest art, one is always aware of things that cannot be said. . ., of the contradiction between expression and the presence of the inexpressible. Stylistic devices are also techniques of avoidance. The most potent elements in a work of art are, often, its silences.
I would only add that the "silences" cultivated by great art are "present" because the work makes room for them in a concrete way. They are incorporated into the work as "ineffable" but real. (The New Critics might have called this ineffable quality "ambiguity," something half-said but not fully said.) The specific way in which, through its style, the work of art invokes a fruitful silence is always still worth attention."
Which recalls Beckett in Endgame: " Yes, in my life, since we must call it so, there were three things, the inability to speak, the inability to be silent, and solitude, that’s what I’ve had to make the best of."