They don't have to know something in this case.

在这种情况下他们不需要知道一些东西。

哈佛公开课 - 计算机科学课程节选

Good, so in the standard story you've got these two crooks, or two accused crooks, and they're in separate cells and they're being interviewed separately--kept apart--and they're both told that if neither of them rats the other guy out, they'll go to jail for say a year.

在故事里有两个罪犯,他们都被指控了 被分别关进了牢房,他们俩被单独提审,两人都知道如果他们不坦白,他们都要只需要坐一年牢

耶鲁公开课 - 博弈论课程节选