A man had two pairs of boots, one with thick soles and the other with thin soles. One morning, he made the mistake of putting one of each of the boots on. While walking, he felt very uncomfortable. "How strange! How is it that my legs aren't the same length today?" He said to himself in surprise.

A passer-by told him, "Your boots aren't a pair."

Hearing this he hurried home to change boots. But when he got home and saw the other boots, he thought for a moment and said," There's no need to change. These other two are not a pair either. One is thick and the other thin."