There is not one Marcel Duchamp, but several. Within this oeuvre Duchamp practiced a variety of modernist idioms and invented an array of contradictory personas - artist and art dealer, conceptualist and craftsman, chess champion and dreamer. This book considers the plurality of identities and practices within Duchamp’s life and art between 1910 and 1941, conducting a synthetic reading of his early and middle career. Taking into account underacknowledged works and focusing on the conjunction of the machine and the commodity in Duchamp’s art, the author notes a consistent opposition between the material world and various forms of measurement, inscription and quantification. Challenging conventional accounts, he describes the readymade strategy not merely as a rejection of painting, but as a means of producing new models of the modern self.