Author Topic: The unexpected hanging.  (Read 598 times)

Online Mr.Obvious

The unexpected hanging.
« on: November 23, 2017, 05:40:16 PM »
I found this in a youtube clip and found it most interesting.
Just thought I'd share.
text taken from wikipedia

 
Quote
   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.

Was the prisoner's reasoning wrong, and why?
"If we have to go down, we go down together!"
- Your mum, requesting 69 last night.


Offline Shiranu

Re: The unexpected hanging.
« Reply #1 on: November 23, 2017, 05:55:26 PM »
He has reasoned that the hanging will not occur it at all, and yet it did. That in itself proves his reasoning was wrong, and it was unexpected.
« Last Edit: November 23, 2017, 09:17:52 PM by Shiranu »
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Offline Hakurei Reimu

Re: The unexpected hanging.
« Reply #2 on: November 23, 2017, 06:19:43 PM »
Because the prisoner's reasoning doesn't even hold for Friday, let alone the rest of the week. Once he's no longer expecting a hanging on that day, a hanging on that day will be unexpected as promised.
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Online Mr.Obvious

Re: The unexpected hanging.
« Reply #3 on: November 23, 2017, 06:38:40 PM »
Yes, but if he were to come to thursday noon and find himself uncalled, and we would go with the notion that the hanging will indeed happen, then he would indeed expect it to be on friday. In that case, it couldn't be an unexpected hanging, like the judge promised.
"If we have to go down, we go down together!"
- Your mum, requesting 69 last night.


Offline Hakurei Reimu

Re: The unexpected hanging.
« Reply #4 on: November 24, 2017, 09:10:00 PM »
Then I guess in your case this hinges on what it means to "expect" a hanging. But anyway, the prisoner's reasoning as stated is wrong.
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Offline Cavebear

Re: The unexpected hanging.
« Reply #5 on: November 26, 2017, 02:47:58 AM »
The whole question is moot if they jailers simply poisoned his food.
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