A merchant deposited some valuable copper with a friend.
When he later asked for its return, the friend said, "Alas, the rats ate all your copper."
"Impossible! Rats can't eat copper."
"These rats can," said his friend.
The merchant went away, but his friend came to him the next day, desperate because his son was missing. The merchant had kidnapped him!
"I saw a raven carry him off," said the merchant.
"Impossible! A raven can't do that!"
"No more than rats eat copper."
The merchant had proved his point; his friend returned the copper, and the merchant returned the boy.
Inspired by: Fables of Aesop and Other Eminent Mythologists by Roger L'Estrange, 451.
Notes: This fable is not part of the classical Aesop tradition; find out more here.
Here is an illustration by Grandville: