The flag.

Three monks are sitting outside their Zendo on a beautiful day. The flag at the top of the building is blowing softly in the wind.

The young monk says, "The flag is moving harmoniously."

The older, wiser monk says, "It is the air which is moving. The flag only reacts passively."

For a long moment, the Zen master sits quietly. Finally he says, "It is the mind which is moving."

—Zen Kōan