I was reading over the MPSIMS and came accross a post called riddles. Turned out it was some guy looking for good riddles he could incorporate into a game he was working on. I offered one, with the answer… and then thought “I wonder if any of the teeming millions at the Straight Dope could handle a riddle of this magnitude” So here I am, in a different message board (because those at the MPSIMS may have read it already) offering you this really difficult riddle. You must promise, however, that you do not go searching for the “Riddles” thread atthe MPSIMS. Here it is
You have died, (or something to that effect) and find yourself at the crossroads between heaven and hell. Before each of the paths stands a man. One man will always tell the truth, the other will always lie. You are granted one question that may be directed at either man, it’s your choice but you know not which of the men lies or tells the truth. What one question do you ask to determine the path to hell and the path to heaven?
Why path would the other man tell me goes to heaven?
Always liar will point to hell path.
Always truth teller, ditto.
Pick opposite.
What would you say if I were to ask you which road leads to heaven?
I heard that the first time a year ago, and I just figured it out.
How old are you?
:rolleyes:
How does that get any information from them?
Always liar will say:
“Path B” (which is really road to hell)
Always truth will say:
“Path A” (which is correct)
However, you stil don’t know who is who, and you’ve used up your one question?
ThisYearsGirl’s answer works, too. If you asked the liar which path leads to heaven, he would say “B”. However, you’re asking him what he would say if you asked him which path leads to heaven, he’ll lie and say he would answer “A”. So he basically “lies about his lie”, reverses himself, and gives you the correct path.
Interesting… I would have thought we’d run through a few more posts before someone got the answer. I liked ThisYearsGirl’s post though… it provided a different twist on the question that I thought was the answer. Had to think it through for a bit just to make sure it made sense 
Heres the answer I was aware of:
“If I ask the other man whether or not you guard the path to hell, will he say yes?”
If he answers ‘NO’ the man you asked the question to guards the path to hell, If he answers ‘YES’ he guards the path to heaven.
It takes a while to work out, so I’d rather leave it up to you if you wish to verify the answer.
And by the way, mavpace, I’m 17. Any particular reason for asking my age?
Nope. That answer works as well. Read the question carefully, and then go through the thought-process of each guard. The truth-teller is a no-brainer. The liar, who realizes he would point to the Hell road, must lie about his answer, and he would point to the Heaven road.
Well I’m not sure if you’re aware but in the movie Labyrinth
http://us.imdb.com/Title?0091369
this riddle comes up, and as you can see from the link the moive was made 14 years ago so this riddle has at least some time under its belt
You can find a slew of similar sorts of puzzles in the logic puzzle books of Raymond Smullyan. These sorts of questions are quite old.
I think Mavpace was just said “How old are you?” as a light-hearted answer to the riddle, not knowing a real answer. I doubt it was an actual question directed to you. I could be wrong.