Question 594958: Transylvania is inhabited by humans, vampires, and werewolves. You cannot tell simply by looking at someone what he or she is. However, humans always tell the truth, vampires always lie, and werewolves sometimes tell the truth and sometimes lie.
In addition, some inhabitants are quite insane and think all true statements are false and all false statements are true. The other inhabitants are sane and correctly distinguish between true and false statements.
So, in Transylvania a false statement could be made out of malice or simply out of honest delusion. For example, a sane human knows the earth is (approximately) round and says so, while an insane vampire believes the earth is not round so will lie and say that the earth is round.
Cody Compton and Bill Devereaux are two Transylvanian friends. One is human and the other is a vampire. Cody says, "I am human" then Bill tells you, "I am human." Cody then tells you that Bill is sane. Which one is the vampire?
Cody, Compton, or Devereaux
Found 2 solutions by jim_thompson5910, tonyclarke:
Answer by jim_thompson5910(35256)   (Show Source):
You can put this solution on YOUR website! Assume that Cody is the vampire
So that would make Bill human (who always tells the truth -- from his point of view)
Cody then states that Bill is sane. Since all vampires lie, this means Bill is an insane human. So he thinks that he's NOT human and does NOT lie.
Therefore, Bill would not say that he was human if he were insane. He would say that he was a vampire. So we have a contradiction.
This means that Bill must be the vampire.
Answer by tonyclarke(17)  (Show Source):
You can put this solution on YOUR website! Cody is the vampire
So that would make Bill human (who always tells the truth from his point of view)
Cody then states that Bill is sane. Since all vampires lie, this means Bill is an insane human. So he thinks that he's NOT human and does NOT lie.
Therefore, Bill would not say that he was human if he were insane. He would say that he was a vampire. So we have a contradiction.
So Bill must be the vampire.
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