I know I said that the final one had been posted... I may have lied
Angels tell the truth, demons lie. Mortals can do either.
Suppose you visit a high society party. No mortals there, only angels and demons. Now, this is a very very high society party, so half of the guests are completely insane. This means that everything that's true they believe to be false and vice versa.
So, if I asked a sane angel whether 2+2 was 4, they'd say "
Yes"
If I asked an insane angel whether 2+2 was 4, they'd think it wasn't and answer "
No"
If I asked a sane demon whether 2+2 was 4, they'd know it was, but lie and say "
No"
If I asked an insane demon whether 2+2 was 4, they'd think it wasn't, but lie and say "
Yes"
There is a box that contains either a green piece of paper or a red piece of paper, you do not know which. If you can guess correctly what colour the paper is, you win a rather large diamond. If you guess wrongly, you must listen to the Greatest Hits of George Bush Volumes 1-100,000. So understandably, you do not want to guess randomly, but be absolutely sure what colour the paper is before you guess.
But it gets worse. The people at the party are speaking in code! There are two words they're using - "
Mushroom"
and "
Artichoke"
. One of them means yes, and one of them means no, and you don't know which is which.
So the riddle is this. What *single* yes/no question could you ask to an inhabitant of the party to find out conclusively what colour the paper is in the box? Bear in mind that you don't know which word means yes and which means no (and they're going to answer with one of the words). And that you don't know whether the person you're talking to is angel or demon. And you don't know whether they're sane or insane.
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