Belling the Cat
Long ago, the mice had a general council to consider what measures they could take to outwit their common enemy, the cat. Some said this and some said that. Eventually a young mouse got up and said he had a proposal to make, which he thought would meet the case.
“You will all agree,” said he, “that our chief danger consists in the sly and treacherous manner in which the enemy approaches us. Now, if we could receive some signal of her approach, we could easily escape from her. I venture, therefore, to propose that a small bell be procured, and attached by a ribbon around the neck of the cat. By this means we should always know when she was about and could easily retire while she was in the neighbourhood.”
This proposal was greeted with general applause, until an old mouse got up and said: “That is all very well, but who is to bell the cat?” The mice looked at one another and no one spoke.
Then the old mouse said, “It is easy to propose impossible remedies”.
Aesop, 6th century BC