One day a farmer went out for a walk with his little son. The farmer wore a pair of wrong shoes. One had thick sole(厚鞋底) but the other didn't. He began to walk and then his feet hurt. When he was just out of the house, he turned to his son and said, “Why is one of my legs longer than the other today?”
The son looked at his father's legs carefully as he was walking and then laughed, “Oh, no, Daddy. Your legs are all right. You're wearing the wrong shoes.” The farmer was very happy to hear that and said to himself, “What a clever son!” Then he asked his son to go back and got the other pair of shoes for him. The farmer had only two pairs of shoes.
When the son ran back to the house, he found that the other pair was also a wrong pair. He had to return to his father with nothing in his hands and said, “It's no use changing them, Daddy! The shoes at home are not a pair, either!”