Are you insane?

If you want your answer to have any effect at all, it has got to be "Yes".

"No" doesn't prove anything. Its rather inconclusive. An insane person thinks he/she is not crazy, as would any sane person. Dont trust a person just because he/she says he/she is not insane.

A person who replies that he/she is crazy is aware of his/her (alleged) insanity. However this clearly indicates an absence of insanity for he/she knows what he/she is. Therefore he/she is definitely not insane (albeit a liar. You may not wanna trust these kind of people either).

I first came across this kind of reasoning in the book Catch-22 by, well, its author. Set during the World War 2(?), the only way for a guy to get out of service(Air force, I think), alive, was to become insane. Once he lost his marbles, he could apply for immediate dischargement. All he needed to do was fill out a form, stating that he had become insane.

BUT, this process clearly indicates that he is in full possession of his wits and, therefore, has to report to work the next day.