Marcel Duchamp fully appreciated the twentieth century's proclivity for certainty and classification and this attitude became an essential component of his art. In this he was not unlike Freud or Einstein or, in his immediate artistic milieu of belle ipoque Paris, Stravinsky or Raymond Roussel. Of the playwright Roussel, Duchamp once noted with admiration that "starting with a sentence ... he made a word game with kinds of parentheses ... His word play had a hidden meaning ... It was an obscurity of another order. Roussel had economically undermined the totalizing tendency of word order, throwing all of its accepted significance into question. He did so by employing, not destroying, the 'givens.' Duchamp's strategy would be similar as is evident in his readymades. Duchamp describes the readymades in terms of what they were not. They "weren't works of art ... weren't sketches" but rather objects, 'things' "to which no art terms applied." Like Roussel's parentheses which are not words but marks (not unlike letters in their most material sense), Duchamp's things were imbued with the accoutrements of art but were not 'retinal' art. Like bracketing, they are inserted into a highly structured world, and in the most economical manner question expose its fundamental nature.