In the fable of "carving a boat for a sword", the boat carver finally failed to find the sword, because the boat is moving relative to the river bank, and the sword sinking into the bottom of the river is static relative to the river bank. In other words, the boat has gone with the flow, but the sword has not gone, so it has not been fished out.

Carving a Boat for a Sword is an allegorical story described by Lv Buwei in Lv Chunqiu Chajin.

Original: A Chu man waded into the river, and his knife fell into the water from the boat. He agreed with the boat and said, "My knife fell from above." The ship stopped at the destination, and the Chu people jumped into the water from the marked place to find the sword. The boat works, but not the sword. If you want a sword, isn't it confusing? .

A Chu man crossed the river, and his sword fell from the boat into the water. He quickly carved a mark on the side of the boat and said, "This is where my sword fell." The ship stopped and (the Chu people) went into the water from the marked place to look for the sword. The ship goes forward, but the sword won't go with it. Isn't it silly to find a sword like this?