MovieChat Forums > Labyrinth (1986) Discussion > The Door Riddle , take two

The Door Riddle , take two

posted 2 years ago by moviechatterer (15638)
2 replies | jump to latest

Theres another thread with similar name but its become bloated with long winded and probably wrong explanations so i thought i'd start a nice new clean one .

I have a newer cleaner simpler way to solve it than the method used in the film , although its basicly the same method technically.

We know the setup:
Two doors (one to certain death , one to all good stuff), two guards , one always lies , one never lies , you get one question.

Traditionally you ask one of them which door the other one would say is good , and do the opposite , which works (regardless of which guard you end up asking - which is the point of the puzzle)
I think its simpler to understand the mechanics of how this works if you do this:

Ask either one of them what HE would say IF you asked him which is the correct door - and go through that same door .

The key thing to realize is you are not straight up just asking which door ,
you are asking "What would he say if you asked that" so if you are talking to the liar he will ALSO be lying about what he'd say - as well as which door to take.

[–] Freddy (1325) 2 years ago

wow might have to watch movie again have dvd old but still great movie agree sort of like the cat in box riddle any way I think whatever was in movie worked ha

[–] aavfreak (3322) a month ago

I've never thought about asking a single door what he himself would say, but it passes the logic test

Scenarios:
This is the door to the castle.
To the non-liar.
Simple and straightforward:
"If I asked you if this is the door to the castle, would you say 'yes?'"
Yes it is the door and since he always tells the truth, he would say yes that it is the door.

To the liar
1. If you asked him directly, "is this the door to the castle," he would say "no," because he's lying about it.
2. If you asked him, "if I asked you if this is the door to the castle, would you say 'yes?'"
3. The truthful answer to this is "no," as we established in #1. He would NOT say "yes."
4. However since he always lies, he would not answer truthfully as "no" and would therefore say "yes."