The Key to the Castle

[Tomm]

Prince X was trying to save Princess Y who was imprisoned in a castle, he needed to enter the castle. At the entrance, there were two boxes. One of the boxes contained the key while the other did not.

They each displayed a message: box A's message was "this box has the key", box B's message was "this box doesn't have the key". You know that either one or both of the messages was lying.

Which box contained the key?

 

[Sabertooth]

Assuming there is only one key, I will go with box B.

Spoiler: No Peeking...

There are three possibilities,

1. Neither is lying,
2. Just one is lying, or
3. Both are lying.

#1 was out per the instructions.
#2 creates a scenario where there are either two keys or none.
#3 yields box B.

 

[Hoaur]

Neither. I swallowed the key.

 

[Sabertooth]

Neither. I swallowed the key.

Whatever you do, don't swallow a fly.
You just might die...

I Know an Old Lady Who Swallowed a Fly

 

[John Bowen]

Going beyond duality is the key to unlock the prison of the mind .