Just finished the biography of Paul Erdős by Paul Hoffman. He quotes an old joke from the American Mathematical Society: "A Physicist and a mathematician are flying cross-country together. Each is keeping a diary of the trip. They fly over a white horse in Iowa, The physicist writes, 'There is a white horse in Iowa.' The mathematician writes, 'There exists, somewhere in the Midwest, a horse, white on top.' "
Artrage painting. Click to enlarge.