Editing 246: Labyrinth Puzzle

{{comic
| number    = 246
| date      = April 9, 2007
| title     = Labyrinth Puzzle
| image     = labyrinth_puzzle.png
| titletext = And the whole setup is just a trap to capture escaping logicians. None of the doors actually lead out.
}}

==Explanation==
This comic alludes to a famous {{w|Knights and Knaves}} logic puzzle, and specifically to the version featured in the Jim Henson movie {{w|Labyrinth (film)|Labyrinth}}, with ''two'' doors and ''two'' guards. One guard always lies, and the other always tells the truth. One of the doors leads to freedom, and you can only ask one guard one question. The solutions to this riddle (and there are several, though all are somewhat similar) involve a tricky question indeed. If you want to give the original puzzle a try for yourself, don't read the spoilers below.
*Solution 1: Ask one guard (it doesn't matter which one) which door the ''other'' guard would say leads out. ''Both'' guards will indicate the same door, which will be the door that ''doesn't'' lead out: the truthful guard knows the lying guard would point to the door that leads to certain death, and says so, while the lying guard, knowing the truthful guard would point to the right door, says the opposite, indicating the door to certain death.
*Solution 2: Ask one guard (it doesn't matter which one) what his answer would be if asked what door leads to freedom. Again, both guards will indicate the same door, which is indeed the door to freedom: the truth guard would, straightforwardly, tell you the truth, while the liar, if asked what door leads to freedom, would point to the opposite, and, if asked his answer, must give the opposite of ''that'' — the true door.

Notably enough, both solutions require that the guards be aware of each other's practice regarding truth and lies, which is not stated in the riddle itself. There's another unspoken rule: that the lie is either a yes or a no. If you asked the liar something, he could lie and say, "I don't know," which would leave you with nothing.

[[Black Hat]] added a third guard here who would stab his spear to [[Cueball]] on every tricky question. But even if the questions from before are not tricky enough to get stabbed, there would be no helpful answer. And if Cueball asks one of the other guards, the answers can't help to find the correct door. The only saving grace is that Black Hat has seemingly forgotten to impose the limit of a single question, but depending on how stab-happy the third guard is or is not, this may not be enough.

The title text presents a typical behavior of Black Hat — no door in fact does lead out of this labyrinth. (Neither door is correct in ''Labyrinth'', either; people paying close attention will note that since ''the guards themselves'' explain the premise, even though one of them supposedly always lies, they can't possibly be taken at face value.)

==Transcript==
:[Three guards with spears stand in front of three doors. Black Hat and Cueball stand in front of the guards.]
:Black Hat: And over here we have the labyrinth guards. One always lies, one always tells the truth, and one stabs people who ask tricky questions.

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Black Hat]]
[[Category:Logic]]
[[Category:Language]]