1803-1882 1817-1862 1874-1954 1887-1968 1912- 20thcentury arts avant-garde(aesthetics) avant-garde(music) cage charles criticismandinterpretationduchamp exhibitions henrydavid history influencecage influenceemerson influenceives influencethoreau john marcel modern musicandliterature postmodernism ralphwaldo silenceinart silenceinmusic unitedstates