Home > Riddles > The two doors
You are in a room with two doors. One leads to freedom, the other to death.
There are two guardians: one always tells the truth and the other always lies, but you don't know which is which. You can only ask ONE question to ONE of the guardians.
What question would you ask to know for sure which door to choose?
Answer: Ask any of the guardians:
"If I asked the other guardian which door led to freedom, what would he tell me?"
Then choose the opposite door to the one they tell you.
Explanation:
This question works because whatever guardian you choose will always point you to the wrong door. That's why, in the end, you choose the opposite.
Analysis by case:
| Case | Answer you get | Point out |
|---|---|---|
| Truthful | "The liar would say: right" | Right |
| Liar | "The truthful would say left; I lie" | Right |
Result: They both point you to the WRONG door → You choose the opposite → Freedom!
Key idea: The question “nests” one lie within another:
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