Good AGM question: The Unexpected Hanging. Can the Wrath solve it?

On Monday, a prisoner is sentenced to hang. The judge tells him that he will be hanged by the end of Friday (of the same week), at noon on whichever day it is, and in the morning of that day he will not know he is to be hanged that day.

The prisoner thinks: so, I definitely can't be hanged on Friday, because by Thursday night I will know it's definitely Friday if I'm still alive. So the last day I can logically be hanged is on Thursday.

But hang on - that means they can't hang me Thursday either, because by Wednesday evening if I'm still alive I'll know it can't be Friday so must be Thursday. So the last day I can logically be hanged is on Wednesday.

Using the same argument, I can't be hanged on Wednesday or Tuesday either and it's already after noon today. So they can't hang me and I'll live on. Yay!

He is then totally surprised when the hangman arrives Wednesday at noon. As the judge promised, he didn't know that the hangman was coming that morning.

Where is the flaw in the prisoner's argument?

(this is probably my favourite paradox)

Posted By: Old Man on November 23rd 2016 at 11:08:35

Message Thread

Good AGM question: The Unexpected Hanging. Can the Wrath solve it? (General Chat) - Old Man, Nov 23, 11:08:35
- Hanging's too good for him (n/m) (General Chat) - Jumbo1, Nov 23, 13:00:52
- My Answer is once he'd used logic to work out he couldn't be hung at all then each morning (General Chat) - megson, Nov 23, 12:21:18
- Pierrepoint's secretary liked to keep his Wednesdays free for ad-hoc hangings? (n/m) (General Chat) - MIKEWALKER, Nov 23, 11:36:04
- Because (General Chat) - Jim, Nov 23, 11:35:08
- Has he gone yet though? (n/m) (General Chat) - CauldRon, Nov 23, 11:34:29
- The judge (n/m) (General Chat) - Adster, Nov 23, 11:31:58
  - Try again. The Ju (n/m) (General Chat) - Adster, Nov 23, 11:32:40
    - Push Pinapple shake the tree (n/m) (General Chat) - Tombs, Nov 23, 11:34:47
      - Pen Pineapple Apple Pen (General Chat) - Ralf Scrampton, Nov 23, 12:11:43
- For all his figuring out and deductions he ignored that (General Chat) - Dunney, Nov 23, 11:30:10
  - case closed. next (n/m) (General Chat) - Tombs, Nov 23, 11:33:28
- Maths graduate sitting this one out. (General Chat) - Arizona Bay, Nov 23, 11:16:46
- quiche or flan? (n/m) (General Chat) - Ralf Scrampton, Nov 23, 11:14:57
  - oh, and yes it can (n/m) (General Chat) - Ralf Scrampton, Nov 23, 11:16:14
- I think the flaw in his argument doesn't really matter much (General Chat) - Tombs, Nov 23, 11:11:25

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