In this situation, do we assume as a given that one of the doors leads to Heaven and that one of the guards is honest?
Because if they're both liars...
But yeah, assuming that, I think Jaden hit the nail on the head, it's actually the sort of thing police use to gauge lie detectors by asking things that are easily answered as true or false (is the sky green?), watch out for anyone who can say 'yes, the sky is green' without the polygraph going nuts 😛