Folk Theorem更多地译为“无名氏定理”，即在重复博弈中，只要博弈人具有足够的耐心（贴现因子足够大），那么在满足博弈人个人理性约束的前提下，博弈人之间就总有多种可能达成合作均衡。无名氏定理有好几个版本，比如两个长寿者之间的博弈，一个长寿者与多个短寿者之间的博弈，也都有类似结论。

参见本版[Young's研讨班主题11]中的笔记。

Exactly. Taking repeated prisioners' dilemma for example, that is why cooperation & cooperation could be one of the Nash in the long run. However, another important implication of the folk theorem is that the Nash in one-short game is still Nash in the repeated game. In other words, Cheat-Cheat is still Nash for repeated PD game.

楼上的补充得对，我前面说得都是无限重复博弈。在有限重复博弈中，只有当事人一方的行为或类型存在某种不确定性时，合作才能发生。否则，无限囚徒困境的纳什均衡仍是不合作。

3楼多次发言，奖励积分100！

Right. In finitely repeated game, again taking PD as an example, player at the last round has no reason to cooperate just as in a one-short game. With backward induction, they have no reason to cooperate at any previous round of the game.

Thank you for your generosity!