Dada. This onomatopoeia suggesting a child's babbling started one of the most important mutations in the history of art. But what is Dada? Born of the First World War, Dada is a movement bringing together both artists and writers. From Zurich in 1916, it spread rapidly to New York, Berlin, Hanover, Cologne and finally to Paris, where it died in 1924. Because of the diversity of its creations, the Dada movement is not an "ism" of the art world: there...