Author Topic: The unexpected hanging.  (Read 108 times)

Offline Mr.Obvious (OP)

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?
E = Mc²

In the end, we are all standing in the dark,
trying to figure out why we are here.
But let us not choose one direction
without proof of where it is headed.

Check your pocket for matches
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as fast friends and relative idiots.

Online 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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Online 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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Offline Mr.Obvious (OP)

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.
E = Mc²

In the end, we are all standing in the dark,
trying to figure out why we are here.
But let us not choose one direction
without proof of where it is headed.

Check your pocket for matches
so we can observe and learn together
as fast friends and relative idiots.

Online 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.
Warning: Don't Tease The Miko!
(she bites!)
Spinny Miko Avatar shamelessly ripped off from Iosys' Neko Miko Reimu

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.
Atheist born, atheist bred.  And when I die, atheist dead!  b 1950