The teacher announces a surprise quiz next week, one whose particular date won’t be predictable in advance. It can’t be given on Friday, since then the students would know on Thursday night that it was coming the next day. But then it can’t be on Thursday, since then students would know on Wednesday night that it was coming the next day. And so on. So the quiz cannot be given on any day. The solution is to introduce intermediate degrees of belief. Each day that the quiz does not occur, the students increase their credence that it will occur the following day, up till Thursday night, when they should still be unsure whether the quiz will come on Friday or instead be cancelled.
- Rescher, Nicholas. 2001. Paradoxes: Their Roots, Range, and Resolution. Chicago, Ill.: Open Court.Google Scholar