Maverick, innovator, desecrator. These terms and more have been used to describe French artist Marcel Duchamp, a man whose ideas on what does and what does not constitute art have been ultimately more influential than his artwork. Creator of Nude Descending a Staircase--perhaps the most famous of all cubist paintings--and inventor of ready-made art, Duchamp was known throughout his life as a resolute challenger of artistic convention. He scrawled a moustache and goatee on a postcard reproduction of the Mona Lisa and called it art; an ordinary ceramic urinal was submitted to a major art exhibition under the title "Fountain"--then sold in the year 2000 for $1.76 million. These sorts of antics foreshadowed the work of later artists, including Andy Warhol, but for Duchamp they were a statement; refusing to accept the standards of the traditional art community, he eschewed line and color for more theoretical and even...