One day a man, hearing that glasses are useful for reading, went to

 a shop to buy glasses.

The shopkeeper showed him a pair of glasses, but he asked for

 another pair. In this way, he continued trying on many pairs of

 glasses, but every time he said. " These are not good. Give me

 another pair, please."

At last the shopkeeper, who was getting angry, said," Sir, can you

 read at all?" The man answered:" If I could read, why would I want

 glasses?"