A man from the state of Chu was taking a boat across a river when he dropped his sword into the water carelessly. Immediately he made a mark on the side of the boat where the sword dropped, hoping to find it later. When the boat stopped moving, he went into the water to search for his sword at the place where he had marked the boat. As we know, the boat had moved but the sword had not. Isn’t this a very foolish way to look for a sword?