On the night of 29 May 1913, the audience at the Théâtre des Champs-Élysées in Paris began rioting during the premiere of Stravinsky's Rite of Spring — the rhythms and dissonances were sufficiently aggressive that the noise of the crowd reportedly drowned out the orchestra, and Diaghilev had the houselights flickered to try to keep order. Six years earlier Picasso had finished Les Demoiselles d'Avignon, a canvas of five women whose African-mask faces and impossible angularity broke pictorial conventions in force since the Renaissance; nine years later Joyce would publish Ulysses in Paris and Eliot would publish The Waste Land in London. The movement these works belong to — modernism — is the self-conscious attempt by Europeans and Americans, between roughly 1880 and 1960, to make the art of a century whose technologies, politics, and self-understanding had broken with everything before it.
What modernism diagnosed was displacement: photography had taken painting's documentary function, recorded sound was taking music's local-performance function, film was taking theater's once-only function, Freud had taken the surface-rational picture of the self, and Einstein had taken absolute space and time. The older artistic conventions had been built for a world that no longer described the audience's experience — and the modernist response, sharpened across very different media, was a single shared move: stop pretending the work is a transparent window onto something else and let the medium be the medium. Cézanne had begun this in his Provençal landscapes of the 1880s and 1890s, structuring the canvas as a built thing rather than a glimpse, and Cubism (Picasso and Braque, 1907–14) extended it by breaking the single viewpoint and admitting that sight itself is constructive. Schoenberg abandoned the tonic in 1909 and devised twelve-tone technique by 1923; Joyce gave a Dublin day six hundred pages of stream of consciousness in Ulysses (1922); Loos in Vienna declared ornament is crime in 1908, and the Bauhaus (Weimar/Dessau, 1919–33) carried the same austerity into furniture, typography, and the glass-and-steel skyscrapers Mies van der Rohe would build for a generation. The unifying claim across painting, music, literature, and architecture was the autonomy of the medium — paint as paint, sound as sound, words as words, the building as a built thing rather than a stage set for civic life. The movement was not univocal (the Russian avant-garde was Bolshevik, the Italian futurists were proto-fascist, the Bauhaus was social-democratic, the surrealists were variously Trotskyist and apolitical), but it was recognizably one historical formation, and most of its signature avant-gardes happened in the four decades 1900–1940. A peculiar feature ran through nearly all of it: a primitivism that reached back — to African masks in Picasso, pre-Christian Russia in Stravinsky, Sanskrit in Eliot, Provençal form in Cézanne — as if the way past the nineteenth century lay through whatever predated it.
Modernism's institutional victory is total: the Museum of Modern Art defines the twentieth-century canon, every art and architecture school teaches modernist work as foundational, concert halls programme Stravinsky and Schoenberg as repertoire, and literature departments have made Joyce, Woolf, Faulkner, and Beckett standard. Its commercial reception lags — most listeners and viewers still prefer pre-modernist or selectively-modernist work, and modernism's appeal is mediated by education rather than by direct popular embrace. Postmodernism (1960s–) defined itself against modernism's seriousness and primitivism, and yet viewed at distance its pluralism, irony, and quotation are recognizably modernist moves continued — the hundred-year break with what came before is now itself the inherited tradition.