Oldest riddle I know. Anyone know the answer?

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TIMMAAYY!!

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There are two doors--one that leads to complete paradise, and one leads to endless pain and suffering.
The doors themselves are identical in every way.

The doors are guarded by two men, one of which cannot lie and one of which cannot tell the truth. These men are also identical in every other way.
You can ask the men any question about the doors, but you can only ask 1 question. What question do you ask to determine which door is which?
 
Well noone is explaining their answers very well, so ill do it.

You ask "If you were the other guard, which door is the one that leads to complete paradise?"

Then take the opposite of whatever the guard is pointing at because,

If the lying guard answered that, he would point to the door to endless pain and suffering because the other guard would answer with the correct door, so he must answer with the wrong one because he always lies.

If the truthful guard answered that he must answer that with the wrong door, because you asked him what would the other guard say is the door of complete happiness. The truthful guard knows the lying guard would lie and give you the wrong answer, so the truthful guard tells the wrong answer as well.

Thus you take the opposite door and your safe.
 
You ask, "If I were to ask the other man which door led to paradise, which door would he point to?" And whichever door he points to, take the other door.
(Because if you asked the liar, he would lie, and point to the pain and suffering door. If you asked the one who tells the truth, he would tell the truth and still point to the pain and suffering door.)
 
i would ask something like what color is my shirt or something along those lines that you can tell immediately if it's true or false
 
This is a logic question and can be answered if one realizes that the TRUTH of a LIE is a LIE, and the LIE of a TRUTH is a LIE. You need one guard to give you the other guard’s answer. Knowing this one could ask a question like, “If I were to ask the other guard which door leads to freedom, what would he say?”
If you ask the guard who always tells the truth, he would tell you the other guard would point you to the door of death. If you ask the guard who always lies, he would tell you the opposite door of the truth-telling guard and point you to the door of death. In either case, both guards will point to the door of death so you should choose the other one.
 
Ask one of them "If I were to ask the OTHER man which door would lead to endless pain and suffering, which door would HE point to?"

After that, take the door that man points to. Why?

If I were talking to the man that cannot lie (i.e. always tells the truth), he'll say that the other man (the liar) will point to the door leading to paradise, since it is not the door that leads to suffering and thus a lie.

If I were talking to the man that cannot tell the truth (i.e. a habitual liar), he'll THINK that the other man (the truth teller) will point to the door that goes to pain and suffering, and knowing that, will point to the door leading to paradise (because he'd be lying about where the truth teller would point).
 
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