A young man in a village was considered a half-wit.
Whenever he was offered a choice between a dime and a nickel, he always chose the nickel. After this had happened many times, a kind old man explained that a dime was worth twice as much as a nickel, advising him to choose the dime in the future.
The half-wit replied, "Oh, I know the difference. But if I chose the dime, they'd stop offering me the choice, and then I'd never even get the nickel."