One day, a man named Ai Zi said to a rich man, "Your sons are foolish and know nothing of the world. How will they manage your property after you're gone?"
The rich man grew angry. "Everyone praises my sons for their intelligence and good virtue," he retorted. "What you say is nonsense!"
"Then let's test them," Ai Zi suggested. The rich man agreed.
The father summoned his two sons. Ai Zi asked them, "Do you know where rice comes from?"
The elder son smiled confidently. "Anyone with sense knows that," he said. "It comes from the kitchen."
The younger son blinked. "You're wrong!" he exclaimed. "It doesn't come from the kitchen. It comes from the bag."
The rich man looked at his sons and flushed with anger. "You fools!" he shouted. "Why didn't you ask me if you didn't know? You're both wrong! Rice comes neither from the kitchen nor from the bag. It comes from the barn!"
The moral of the story is that pretending to know something you are ignorant of often leads to foolish actions.