A small village farmer owed a large sum of money to a very unkind and ugly old man.
The farmer, unable to pay, had a very beautiful daughter that the old lender was attracted to. So, the lender proposed a bargain.

He said he would forgive the debt if he could marry the farmer's daughter. The farmer and his daughter were both horrified at this proposition so the old lender suggested another way to determine the outcome of his proposal. He would put two pebbles, one black and one white, into an empty money bag. Then, without looking, the daughter would pick one of the two pebbles.

If she picked a black one, she must marry the lender, and the debt to her father is eliminated.

If she picked the white pebble, she wouldn't have to marry him and the debt is also eliminated.

If she refused to pick a pebble, her father will go to jail.

As it happens, this was taking place on the road in front of the farmer’s house and the road was paved with many pebbles. While speaking, the old lender leaned forward and picked up two pebbles. As he did this, the daughter noticed he had picked up two black pebbles and put them in the money bag.

In this dilemma, the girl faced three options each with a disastrous outcome.

- She could refuse to take a pebble and have her father imprisoned.
- She could show there were two black pebbles and expose the money-lender as a cheat.
- She could pick a black pebble and sacrifice herself to save her father from his debt.

Instead, she plunged her hand in the bag, picked a pebble and intentionally fumbled with it, whereupon it fell onto the pebble-strewn path and immediately became lost among all the other pebbles.

"Oh, how clumsy of me," she said. "But never mind. If you remove the pebble that is left, you will be able to tell which one I picked."

Since the second pebble was black, the first had to have been white. The old lender, surprised and angry at being beaten at his own game didn’t dare admit to his cheating and was forced to relieve the farmer of his obligation.