The right way to heaven
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The right way to heaven is a riddle involving strong logical considerations. It seems unsolvable on first examination but features a surprisingly elegant solution.
[edit] The riddle
You are dead and walk on a way in the sky. Eventually you reach a parting of the ways. One way leads to heaven, one to hell. At the parting you see three ghosts, marked with the letters A, B and C. Those ghosts are the ghosts of Gandhi, Goebbels and Hitler but you don’t know which one is which. You know that Gandhi always tells the truth, Hitler always lies and Göbbels lies and tells the truth randomly. Since you don’t know which way is the right way to heaven you have two (yes/no) questions to find out. Each question must be addressed to one ghost.
[edit] The hint
The biggest problem in this riddle is Goebbels, because his answers are random and therefore useless. So a good strategy would be to eliminate him with the first question. If that could be achieved, the second question may be comparably simple, since one has only to devise a question containing a possible “double lie” by Hitler, yielding the same answer as Gandhi would give.
[edit] The solution
The first question to C could be: ”Is A more honest than B?”
If the answer is “yes”, the second question is directed to B, if “no” the second question is addressed to A.
If C is Gandhi, he will say that Goebbels is more honest than Hitler; so a yes means A is Goebbels and a no means B is Goebbels. If C is Hitler he will lie and say Goebbels is more honest than Gandhi and the same answers apply. Either way you have identified Goebbels so you can be certain that your second question will be to Gandhi or Hitler, (note that if C is Goebbels it does not matter who you are directed to for the second quesion as it will be either Gandhi or Hitler).
The second question (addressed to A or B, which has to be Hitler or Gandhi) could be: “Do I assume right, that if I ask you, whether the left way leads to heaven, you would answer “yes”?”
If the guess is right, Gandhi would answer “yes” and leads us to heaven. Hitler would reason, that his answer to ”is the left way the right way” is “no” because he has to lie. So the assumption, that he would answer “yes” is false. The very question about the assumption “Do I assume right…” he has to answer with “yes” because he’s again forced to lie. So both answers are the same and both lead us to heaven. If the guess is false, we also get the same right answer “no”.
