hardlogic

There are two doors and there is one guard for each door. One door leads to life and the other leads to death. You have only one question to ask and you can only ask one guard. One of the guards always tells the truth and the other always lies. What question would you ask to find out which door is the door to life?

You would ask: "If I were to ask the other guard which door leads to life, what would he say?" The guard that tells the truth knows that the other guard would lie. So he tells the truth and points to the door that leads to death. The guard that lies knows that the other guard would tell the truth. So he lies and points to the door that leads to death. Both guards point to the death door.

Why this works

This riddle cleverly uses the concept of indirect questioning to navigate the truth and lies of the guards. By asking, "If I were to ask the other guard which door leads to life, what would he say?", you create a scenario where the truth-telling guard reveals the lie, and the lying guard distorts the truth. In both cases, the answer given will always point to the door that leads to death, allowing you to confidently choose the opposite door for life. This riddle showcases the power of logical reasoning and the clever use of opposites!

Common Wrong Answers

“Which door leads to life?”

Asking which door leads to life does not account for the possibility of deception. The truthful guard would point to the correct door, but the lying guard would point to the wrong one, leaving you unsure which door actually leads to life.

“Is the left door the one that leads to life?”

This question can lead to confusion because the truthful guard would say 'yes' or 'no' based on the actual situation, but the liar would respond in the opposite manner. You would still not have a clear indication of which door is safe.

“Can you tell me the truth about the other guard?”

This question does not directly help you identify the correct door. The truthful guard would give an accurate description of the liar, but it wouldn’t provide any information about which door leads to life, leaving you without a definitive answer.

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