The Old Man and the Two Doors, A Philosophical Puzzle

Once upon a time, there was an old philosopher who stole some gold from the king. Obviously, the king was extremely mad and decided to execute the old man. On the day of the execution, the king thought over the situation and realized that it was a little harsh. Thus, he gave the old man a chance to live in riches (yay), or die a very slow and painful, sickening, bloody death (oh god what the fu~).

Alright! Lets get to the problem!

The old man was presented with two doors:

  • One door led to riches and life (that’s good).
  • One door led to inhumane torturous horrible bad death (that’s a bit much doncha think?).

Now, I know what you’re thinking(woah, is there some mind reading stuff going on here?). “But Austinnnn, that’s a 50–50 chance! Isn’t there some kind of twist?” Yep!. The king was wise and hence decided to give the philosopher something more than a mere 50–50 chance. So,he added a twist.

There were two guards,

  • One who always tells the truth(aw what an angel)
  • One who always tells lies,:and your commentary is getting annoying(listen here you sack of shi~)

The old man could ask one of them one question(only one?). Only one. Plus, he didn’t know which guard was guarding which door(I guess that would be a bit too easy).

The old man sat and thought for a very long time. An hour passed. 2 hours(I thought you said he was smart) passed. Finally, something clicked in his weary brain(finally). The first was that the commentary was bad(no he didn’t liar), and the second was that he had it figured out.

He realized that he could find which door was the right one, AND which guard was the liar. After realizing that just finding which guard was who wasn’t enough, he started thinking of other ways, until he finally realized that by asking a single question, he could do both. He could ask, “If I were to ask the other guard which one was the good door, what would he say?”.

  • If he asked the guard who always told the truth, the question, then of course he would have responded with the truth, and said that ‘the other guard would say that the good door is the bad one’.
  • If he asked the guard who always lied, the question, then he would have responded with a lie, and said that ‘the truth guard would say the good door is the bad door.’

So no matter which guard he asked, he would have been able to know which door to go through(the opposite one right?). Exactly! (I mean….unless he wanted to have some….fun)

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