In 1949 an aristocratic bohemian named Jacques Mah? de La Villegl? was walking down the Boulevard Montparnasse in Paris when a billboard of shredded posters caught his eye. The colors and jagged shapes looked like an abstract painting. So he ripped them down, mounted them on canvas, and pronounced it Art. "You see the street was really my at?lier", says Villegl?, now 95- years-old and still making art in Paris. His work hangs in every major contemporary...