Mind - The wind is not moving

"Once when the wind was whipping the banner of a temple, the Sixth Patriarch of Zen witnessed two monks debating about it. One said the banner was moving, one said the wind was moving. They argued back and forth without attaining the principle, so the Patriarch said, 'This is not the movement of the wind, nor the movement of the banner; it is the movement of your minds.'The two monks were both awestruck."