"Han Feizi".

The Chu people who had shields and spears praised them by saying: "My shield is so strong that nothing can sink it." They also praised their spears by saying: "My spear is so sharp that nothing can sink it. ." Or say: "How about using Zi's spear to trap Zi's shield?" This person can't respond. Everyone laughed. A shield that cannot be trapped and a spear that cannot be trapped cannot exist in the same world.

During the Warring States Period, there was a spear and shield seller in Chu State. He first boasted that his shield was very hard and said: "No matter what you use, it can't be damaged." Then he boasted about himself. His spear was very sharp and he said: "Everything can be destroyed by it." The people in the market asked him: "If you use your spear to pierce your shield, what will happen to them?", the man could not answer. Everyone laughed at him. A shield that cannot be pierced and a spear that cannot pierce the shield cannot coexist.