Two men were arguing about a flag flapping in the wind. "It's the wind that is really moving," stated the first one. "No, it is the flag that is moving," contended the second. A Zen master, who happened to be walking by, overheard the debate and interrupted them. "Neither the flag nor the wind is moving," he said, "It is MIND that moves."

(In other versions of this story,
the master says it is the HEART
that flaps)