Day-knights tell the truth in the day and lie at night. Night-knights lie in the day and tell the truth at night.
A:B is a day-knight.
B:A is a night-knight, and it is night.
What are A and B, and is it day or night?

Outside of the twilight hours, it must be day.
A is a night-knight, and, it being day, A's statement,
"B is a day-knight", is a lie. B is a night-knight.
As B is a night-knight, and, it being day, B's statement,
"A is a night-knight, and it is night", is a lie.
Though A is indeed a night-knight, the compound statement
is a lie as it is day.

 

Posted by Dej Mar on 2011-03-21 14:16:16