There is a land where every inhabitant is either a day-knight or a night-knight. Day-knights tell the truth in the day and lie at night. Night-knights lie in the day and tell the truth at night. One inhabitant once said, "It is day." Is the inhabitant a day-knight or a night-knight?

(In reply to Solution by Kenny M)

As we neither are given that the statement was made independent of an answer to a question nor what the pronoun "it" is in reference to (such as "When is it that your statements are lies, day or night?"), or even if the statement was uttered during the time of twilight (a period of time when it is neither day nor night) as we are not given the veracity of how day-knights and night-knights would speak during such time, we can not be 100% sure it was made by a day-knight, but it would be most probable that it was made by one.

As the English language can be unclear, it also can be said that the inhabitants are "knights", who, by definition, tell only the truth, and both can lie (be in a position in which one's body is flat on a surface, as they might be if they are abed for sleep), thus it could have been made by any of the inhabitants.

Posted by Dej Mar on 2011-03-09 00:17:35