Can you solve the three gods riddle? – Alex Gendler

Can you solve the three gods riddle? – Alex Gendler

View full lesson: http://ed.ted.com/lessons/can-you-solve-the-three-gods-riddle-alex-gendler

You and your team have crash-landed on an ancient planet. Can you appease the three alien overlords who rule it and get your team safely home? Created by logician Raymond Smullyan, and popularized by his colleague George Boolos, this riddle has been called the hardest logic puzzle ever. Alex Gendler shows how to solve it.

Lesson by Alex Gendler, animation by Artrake Studio.

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20 Responses

  1. All animals are just Slightly different horses says:

    Actually he told you that it was a long way to earth with the final question

  2. billy bob says:

    Hmm the gimmick of this puzzle seems to be the assumption that the aliens are able to stand in a straight line. What if they are inter-dimensional extra-terrestrials without bodies? Is the problem still solvable?

    My 3 questions were:

    1) Does this Artifact belong to You?
    2) Does this Artifact belong to Arr?
    3) Are you Arr?

  3. SaNaTo Sky says:

    I hope this comment can be a Little Help to understand the Riddle.
    and dont forget correct me if im wrong.. let learn together.. haha
    =================================================================
    If I Asked “…” Would you answer “ozo” means:
    ozo = yes
    ulu = no

    *basicly adding “Would you answer ‘ozo’ ” is making Tee and Eff always say the truth
    *explain how to get ozo = yes for us in first comment
    =================================================================
    1 = Tee , using ozo for yes, ulu for no
    2 = Eff , using ozo for yes, ulu for no
    3 = Arr , unpredic answer
    o = yes
    u = no

    – = mean answer for the side,

    -o : means answer for left side yes
    o- : means answer for right side yes
    -u : means answer for left side no
    u- : means answer for right side no
    o : means answer for own side yes
    u : means answer for own side no

    ==================================================================
    Test Case for the answer:
    1. The key is, ask is the other lord is Arr first (becase Arr Can NOT be trusted)
    2. Choose lord who is not Arr based on first question and ask is that lord is Tee ( If the first lord give wrong answer, this second lord will give u a right answer and who is. Because the secord lord is always Tee or Eff, who already traped with right answer, and if the first lord already giving the right answer so this secord lord will give right answer too)
    3. Ask Same lord based on first answer, is lord with first answer is arr ( This question make u know, is that lord was Arr)

    *anyway with first answer from the first lord u will never asking Arr for next question. so the second lord will give u right information.

    +++++++++++++++
    IF Arr in the mid. +
    +++++++++++++++
    1 3 2 – ozo – ulu – ozo –
    -o asking number 3 : num 1 is arr ? and if the answer is o (means yes),
    choose num 2 for next question (because predicted is not arr)
    u asking number 2 : are u Tee? and its will answer u (means no)
    -o asking number 2 : num 3 is arr? and its will answer o (means yes)

    1 3 2 – ulu – ozo – ozo –
    -u asking number 3 : num 1 is arr ? and if the answer is u (means no),
    choose num 1 for next question (because predicted is not arr)
    o asking number 1 : are u Tee? and its will answer o (means yes)
    o- asking number 1 : num 3 is arr? and its will answer o (means yes)

    2 3 1 – ozo – ozo – ozo –
    -o asking number 3 : num 2 is arr ? and if the answer is o (means yes),
    choose num 1 for next question (because predicted is not arr)
    o asking number 1 : are u Tee? and its will answer o (means yes)
    -o asking number 1 : num 3 is arr? and its will answer o (means yes)

    2 3 1 – ulu – ulu – ozo –
    -u asking number 3 : num 2 is arr ? and if the answer is u (means no),
    choose num 2 for next question (because predicted is not arr)
    u asking number 2 : are u Tee? and its will answer u (means no)
    o- asking number 2 : num 3 is arr? and its will answer o (means yes)

    +++++++++++++++++++++++
    If in the middle is tee or eff +
    +++++++++++++++++++++++

    1 2 3 – ulu – ozo – ulu –
    -u asking number 2 : num 1 is arr ? and if the answer is u (means no),
    choose num 1 for next question (because predicted is not arr)
    o asking number 1 : are u Tee? and its will answer o (means yes)
    u- asking number 1 : num 2 is arr? and its will answer u (means no)

    3 2 1 – ozo – ozo – ulu –
    -o asking number 2 : num 3 is arr ? and if the answer is o (means yes),
    choose num 1 for next question (because predicted is not arr)
    o asking number 1 : are u Tee? and its will answer o (means yes)
    -u asking number 1 : num 2 is arr? and its will answer u (means no)

    2 1 3 – ulu – ulu – ulu –
    -u asking number 1 : num 2 is arr ? and if the answer is u (means no),
    choose num 2 for next question (because predicted is not arr)
    u asking number 2 : are u Tee? and its will answer u (means no)
    u- asking number 2 : num 1 is arr? and its will answer u (means no)

    3 1 2 – ozo – ulu – ulu –
    -o asking number 1 : num 3 is arr ? and if the answer is o (means yes),
    choose num 2 for next question (because predicted is not arr)
    u asking number 2 : are u Tee? and its will answer u (means no)
    -u asking number 2 : num 1 is arr? and its will answer u (means no)

    *in the end video (4:30) , there is an explanation that impossible to know what is ozo or ulu mean,
    even with this logic we already find who is Tee, Eff, and Arr.

    ====================================================================
    This reading just my opinion. if u guys have another opinion, please correct my ready.. 🙂
    The genius one is people who make this riddle -> Raymond Smullyan. (based on video)

  4. Wade-Kun Damones says:

    My question is: why would the overload who lies answer yes? That whole explanation about two negatives making a positive works in math equations, but doesn’t make sense here. Why would the alien who lies simply not lie?

  5. Sarah Grogan says:

    I was going to say “point to my rocket” and then I have one who points in the right direction and one that points on the wrong, say 2 pointed to the right one and one pointed to the wrong one, I know that he lies, then I ask the two who told the truth “point to the rocket” and one will point and one maybe won’t, if they both point to the rocket I will repeat the question until one doesn’t point, then I know who is who

  6. Nadine says:

    wanna hear a joke?

    >>Read more<<

  7. Y2E gaming says:

    this was so easy that it would pissed me off if someone said it was the hardest riddle.

  8. Diorno Diovanna says:

    But… Just knowing who is who doesn’t help you figure out who the artifact belongs to, does it?

  9. Ara 101 says:

    Hi Random Person scrolling through the comments!😁

  10. Aqua Warriorcat says:

    To Be Honest, I would just ask Tee if he knew how to talk – if he said Ulu, Ulu means yes, if he said Ozo, Ozo means yes, yeah…

  11. Jack Raftery says:

    4:36 When you ask a question in math class and the teacher’s answer just confuses you even more

  12. Flare Strider says:

    Ask each one what the square root of 25 is?

  13. Meow Meow says:

    How I would identify the words ” ozo” or “ulu” would be by telling the truth alien that my doggy is white, and asking it if it agrees with me. If it responds with “OZo”, it would mean “yes”.

  14. Sally Tse says:

    Today is. My birthday

    Can I get some likes plz

  15. Matthew Harrity says:

    I think I solved this another way with one assumption. That is, if you ask one of the aliens a question they do not know the answer to, they will remain silent. This is because if the liar or truth teller were to try and take a guess, they could be telling the truth or lying (respectively), thus break their own law.

    The way I solved it, you ask one of the aliens (say alien 1), “if you were to answer a question ulu, would alien 2 agree with you?” Essentially, I am asking if they would have the same response. Now, unless he is silent (meaning that alien 2 is the alien that lies sometimes because neither of the other two know whether he will lie or not), we move to alien 2 and ask him a similar question, “if you were to answer a question with ulu, would alien 3 agree with you?” We do this to identify if either of these aliens are the alien that lies sometimes. If we get two answers, that means that alien 1 is the one that lies sometimes. Now, we know which alien is the sometimes liar (from either one or two questions- if it is one question, we just ask alien 3 about alien 1) so, from here, we determine if ulu is yes or no from asking one of the aliens that isn’t the sometimes liar “would [the other alien that isn’t the sometimes liar] say that [the alien we identified as the sometimes liar] is the sometimes liar?”
    Going back to the answers we would get from the initial two questions: the liar will always answer incorrectly while the truth teller will always answer correctly. If we were to ask the truth teller and he says ulu, the liar would say ozo. They always have opposite responses (liar would say yes and truth teller would say no). Now, if we were to ask either the liar or the truth teller to answer the final question, BOTH of their responses would be the same. This is because the truth teller knows that the liar would not say that the sometimes liar is the sometimes liar (thus answer negatively) and the liar, knowing that the truth teller would answer correctly, would lie and say that the other non-sometimes liar would not identify the sometimes liar (also answering negatively). So, from this, we can deduce that whichever alien answered identically from one of the first two questions to the third is truth teller and if they were different answers, it is the liar. Thus, we have identified all three aliens.

    Thoughts?

  16. Sjk Rofl says:

    If they speak english just ask them what “ulu” means

  17. Gaurav Youtube says:

    A BETTER SOLUTION!!!
    Plz go though it once… these are even better and simpler ques..
    since they can only answer in yes or no but they have to answer …
    Case I: Let him not be Arr.
    ask the first alien lord, “have u stopped fucking Arr’s lady? he would reply no matter what.. Arr will kill him and u would know who is Arr and since only one of them is left.. as third is dead.. u can use your IQ and identify who is that alien..
    Case II: Let the first one be Arr..
    ask the same ques and if nothing happens… u get that he is Arr…ask the second one two ques that are always positive..like are you alien and if 2+2=4??
    AND U R DONE…
    NOTE: this is the basic method… feel free to alter the ques itself by add.. say..”have u stopped fucking Arr and Tee’s ladies”.. thanks for reading…

  18. Antonio Luna The Badass Philippine General says:

    What if I asked any one of them “This statement is false, ozo or ulu?”

  19. krtek says:

    these lessons used to be good, now it’s just crap. Sad out of ideas

  20. Loki Love says:

    So you learned the language but don’t know yes from no? Hmmmmmmm

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