A man has died and he sees two doors. One leading to hell, one leading to heaven. The door to heaven is guarded by an angel that only tells the truth. De door to hell is guarded by a demon that only tells lies. But you can't tell who's the angel, or who's the demon,- they both look the same to you. You may only ask one question to one of them. And thats the only question you can ask before going into a door. They can only answer with yes and no.