(November 23, 2017 at 7:01 pm)Mr.Obvious Wrote: The Unexpected Hanging Paradox
Taken from wikipedia:
A judge tells a condemned prisoner that he will be hanged at noon on one weekday in the following week but that the execution will be a surprise to the prisoner. He will not know the day of the hanging until the executioner knocks on his cell door at noon that day.
Having reflected on his sentence, the prisoner draws the conclusion that he will escape from the hanging. His reasoning is in several parts. He begins by concluding that the "surprise hanging" can't be on Friday, as if he hasn't been hanged by Thursday, there is only one day left - and so it won't be a surprise if he's hanged on Friday. Since the judge's sentence stipulated that the hanging would be a surprise to him, he concludes it cannot occur on Friday.
He then reasons that the surprise hanging cannot be on Thursday either, because Friday has already been eliminated and if he hasn't been hanged by Wednesday noon, the hanging must occur on Thursday, making a Thursday hanging not a surprise either. By similar reasoning he concludes that the hanging can also not occur on Wednesday, Tuesday or Monday. Joyfully he retires to his cell confident that the hanging will not occur at all.
The next week, the executioner knocks on the prisoner's door at noon on Wednesday — which, despite all the above, was an utter surprise to him. Everything the judge said came true.
Where did the prisoner's reasoning go wrong.
What the prisoner didn't realize was that the judge was indeed going to let him off - the prisoner's reasoning was flawless.
Unbeknownst to the prisoner, however, was that the judge received a telegram on Wednesday morning informing him that the prisoner was in fact the Mysterious Stranger who had robbed the Greenland Express mail train 11 years earlier, making off with kr14 and a tin of pickled lumpfish. Escaping on foot was arduous (to say the least), so the robber hitched a lift on a milk cart drawn by a pair of fighting bull merinos. Deciding to hold onto his kr14 for a rainy day, he gave the lumpfish to the cart driver to thank him for his trouble.
Delighted at his good fortune, the cartsman arrived home and asked his wife (Babette) to prepare the fish for that evening's supper. Sadly, a few hours after eating their meal, both the cartsman and his good lady succumbed to botulism due to consuming tainted fish.
Babette, it transpired, was actually the judge's twin sister, and he had been mourning his loss for more than a decade. Realizing that he had his sister's killer within his power at long last, the judge went back on his word to the prisoner, and had him executed forthwith.
I fucking love logic puzzles.
Boru
‘But it does me no injury for my neighbour to say there are twenty gods or no gods. It neither picks my pocket nor breaks my leg.’ - Thomas Jefferson
