In 1917, Marcel Duchamp sent out a 'telegram' in the guise of a urinal signed R. Mutt. When it arrived at its destination a good forty years later it was both celebrated and vilified as proclaiming that anything could be art; from that point on, the whole Western art world reconfigured itself as 'post-Duchamp'. This book offers a reading of Duchamp's telegram that sheds new light onto its first reception, corrects some historical mistakes and reveals that Duchamp's urinal in fact heralds the demise of the fine arts system and the advent of what Thierry de Duve calls the 'Art-in-General' system. Further, the author shows that this new system does not date from the 1960s but rather from the 1880s. Duchamp was neither its author nor its agent, but rather its brilliant messenger.