Art.

“Grave this on your memory, lad: a world is supported by four things,” she held up four big-knuckled fingers.  “The learning of the wise, the justice of the great, the prayers of the righteous, and the valor of the brave. But all of these things are as nothing,” she closed her fingers into a fist, “without a ruler who knows the art of ruling. Make that the science of your tradition!”

Frank Herbert, Dune