"The historic avant-garde (but here I would also consider avant-garde a metahistorical category) tries to settle scores with the past. "Down with moonlight"--a futurist slogan--is a platform typical of every avant-garde; you have only to replace "moonlight" with whatever noun is suitable. The avant-garde destroys, defaces the past: Les Demoiselles d'Avignon is a typical avant-garde act. Then the avant-garde goes further, destroys the figure, cancels it, arrives at the abstract, the informal, the white canvas, the slashed canvas, the charred canvas. In architeture and the visual arts, it will be the curtain wall, the building as stele, pure parallelepiped, minimal art; in literature, the destruction of the flow of discourse, the Burroughs-like collage, silence, the white page; in music, the passage from atonality to noise to absolute silence (in this sense, the early Cage is modern).
But the moment comes when the avant-garde (the modern) can go no further; because it has produced a metalanguage that speaks of its impossible texts (conceptual art). The postmodern reply to the modern consists of recognizing that the past, since it cannot really be destroyed, because its destruction leads to silence, must be revisited: but with irony, not innocently."
Umberto Eco, "'I Love You Madly,' He Said Self-consciously", The Truth About the Truth, Pg. 32