The mystery behind the most famous mutilation in art history may finally have been solved. A scholar has found evidence that a distraught Vincent van Gogh slashed his ear after learning that his brother, Theo, on whom he depended financially and emotionally, was about to get married. Martin Bailey, who has written a book on van Gogh and curated two exhibitions of his work, devised his theory after meticulous detective work on a letter in a painting...