
'The Hardest Logic Puzzle Ever' Made Even Harder - olalonde
http://www.technologyreview.com/view/428189/the-hardest-logic-puzzle-ever-made-even-harder/
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ColinWright

        There's a caveat, of course: you have to be
        talking to omniscient Gods who understand
        English but refuse to speak it. 
    

Another, perhaps bigger caveat is that they Gods have to be perfect logicians.

There's a simple version of this puzzle:

    
    
        Two doors are guarded, each by one sentry.
        One sentry always speaks the truth, the
        other always lies.  Behind one door lies
        death, behind the other, freedom.  You
        have one "Yes-No" question.  What do you
        ask?
    

The trick is to ask a double question in one:

    
    
        If I asked you if this is the door to freedom,
        would you answer "Yes"?
    

My experience is that most people can't answer that question correctly, even
when it's explained carefully in several different ways. People aren't logic
machines, and English (and probably _every_ natural language) is a poor
vehicle for such discussions.

