When Marcel Duchamp met Joseph Cornell in New York in the early 1930s, they exchanged vivid recollections of Paris. In the course of the conversation, it came out that the New York-born Cornell had never visited the French capital, but had got all his knowledge of its topography from old travel guides. Duchamp was not easily astonished, but this had him stumped.Cornell (1903-72) is a unique figure in art history: someone who hardly thought of himself as an artist – more as a maker of things in “a kind of Sunday spirit” – yet arguably had a wider influence on later art than any other artist of the twentieth century. His trademark arrangements of ephemera in “shadow boxes” left their mark on Pop, installation and conceptual art. Duchamp followed his lead