ANEW nonliterary culture exists today, of whose existence, not to mention significance, most literary intellectuals are entirely unaware,” wrote Susan Sontag in her groundbreaking 1965 essay, “One Culture and the New Sensibility.” The new sensibility, she argued, collapsed the distinction between highbrow and lowbrow, embraced popular culture, celebrated modernist music and painting the masses had little taste for, and advanced a new understanding of the senses. In a milieu that took as its dictate to “modify consciousness” and to “organize new modes of sensibility,” Marshall McLuhan played the role of leading commentator, explaining the new world to the rest of us.