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Two Paths, Two Angels, One Question
You have died (sorry!). In front of you are two paths, one goes left and the other goes right. There is also a sign which reads:
" One path before you leads to Hell, the other to Heaven. You must choose between them. The paths are guarded by two angels [at this point they miraculously appear]. The angels are identical except that one angel will always tell the truth and the other will always lie. You are allowed to ask one question, to which both will answer."
What question do you ask to work out which is the right path?
To gain any information about which path to choose, you must ask a question to which both angels give identical replies. A question to which one angel replies "Left" and the other "Right" is no use, because you don't know which angel is telling the truth.
With a dichotomy (a question with only two answers), lying about the correct answer is the same as telling the truth about the wrong answer.
"Which path would would the other angel say was the path to Heaven?"
(or something similar)
Here is the correct question again:
Which path would would the other angel say was the path to Heaven?
Break that down into two parts. Firstly, what does each angel think the answer is and secondly, what does each angel actually say the answer is.
To make things clearer, we will also assume that the path to Heaven is on the left.
Truthful Angel
1) This angel knows that the path to Heaven is on the left and that therefore the lying angel, if asked which was the path to Heaven, would respond with a lie and say that it was the one to the right.
2) As this angel tells the truth, he says what he thinks the other angel would say i.e. "Right".
Lying Angel
1) This angel also knows that the path to Heaven is on the left and that therefore the truthful angel would respond with the truth and say that it was the one to the left.
2) As this angel always lies, he says the opposite of what he actually thinks the other angel would say i.e. "Right"
We can see that both answers are the same which was is essential (see clue one). We can also see that the truth about a lie and a lie about the truth have both given a lie (see clue two). Although both angels have said "Right", we can deduce that the path to heaven is actually the one to the left. Of course, if it starts heading steeply downhill, we might want to reconsider.
(Thanks to a fellow 'intloafer' for sending this in.)
Know any other questions? E-mail them to WebMaster@IntellectualLoafing.com
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