Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The Solution To The Hardest Logic Puzzle Ever!

  1. Feb 16, 2005 #1
    Seems like no one got it so here it is without further adieu (sp?) http://people.ucsc.edu/~jburke/three_gods.pdf [Broken]
    Last edited by a moderator: May 1, 2017
  2. jcsd
  3. Feb 16, 2005 #2


    User Avatar
    Science Advisor
    Homework Helper

    Ouch,mamma,that was...hm...2 smart for me...:cry:

  4. Feb 17, 2005 #3
    I understand how the puzzle was solved, but I have two problems with it.
    1. shouldn't be able to make up words "iff"
    2. the second question "...iff Rome is in Italy" isn't logically correct. Can't assume Rome is in Italy
  5. Feb 17, 2005 #4

    iff=if and only if is standard vocabulary in math and philosophy
  6. Feb 17, 2005 #5
    new one for me, why not say if and only if
  7. Feb 17, 2005 #6
    because mathematicians are notoriously lazy
  8. Feb 17, 2005 #7


    User Avatar
    Science Advisor
    Homework Helper

    There's a Rome in NY state as well,if i'm not mistaking...:wink:So Trib's right...

  9. Feb 17, 2005 #8
    I figured out the 3 component puzzles before reading on and got answers using XOR instead. Being a computer science major, I thought of XOR before XNOR (XNOR is iff). It works out the same, just reversed.

    Still, Boolos limited himself in his choice of questions; if you ask True or False what Random says next, they can only be silent.
  10. Feb 17, 2005 #9
    Ok, that is one brilliant puzzle.
  11. Feb 17, 2005 #10
    so by this iff reasoning we can ask things like:
    Are you goign to say yes, the 2nd guy no, and the thrd guy yes to the question "blah blah"

    I think thats sort of a copout, like asking multiple questions in one.

    The original problem should not limit you to asking "only 3 questions" but getting only 3 responses.
  12. Feb 17, 2005 #11
    You still get 3 responses.
  13. Feb 18, 2005 #12


    User Avatar
    Gold Member

    I don't know why he assumes the False god would lie about a biconditional (or, for that matter, any compound proposition) but not about its constituent propositions. In [S <-> P], there are 3 propositions in question: S, P, and [S <-> P]. It makes as much sense, if not more, to assume False would lie about all 3. It doesn't effect his conclusion, but still...
    Eh, I was going to maybe write and ask him but I see that's unfortunately not possible. Great puzzle still.
    Last edited: Feb 18, 2005
  14. Oct 4, 2006 #13
    Bump. I still keep getting PM's asking for the solution to this problem all the time.
  15. Nov 10, 2006 #14
    Last edited by a moderator: Apr 22, 2017
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook