The Dog and the Meat.
A dog with a piece of meat in his mouth was crossing a bridge over a placid stream. On looking down he saw another dog with a precisely similar piece of meat in the water below him. "That's a singular incident," he thought to himself as he prepared to jump in. "But hold a minute! The angle of incidence is always equal to the angle of reflection. Upon reflection, I find that the other dog and the meat are only optical phenomena." And he trotted on his way to Boston without further thought about the matter.
