“A common reaction of someone caught in a Prisoner’s Dilemma is that “there ought to be a law against this sort of thing.” In fact, getting out of Prisoner’s Dilemmas is one of the primary functions of government: to make sure that when individuals do not have private incentives to cooperate, they will be required to do the socially useful thing anyway. Laws are passed to cause people to pay their taxes, not to steal, and to honor contracts with strangers. Each of these activities could be regarded as a giant Prisoner’s Dilemma game with many players. No one wants to pay taxes because the benefits are so diffuse and the costs are so direct. But everyone may be better off if each person has to pay so that each can share the benefits of schools, roads, and other collective goods (Schelling 1973). This is a major part of what Rousseau meant when he said that government’s role is to make sure that each citizen “will be forced to be free”

其实还可以从法律改变了囚徒困境的payout，让背叛的收益相比较合作来说没有那么大，甚至低于合作的收益。就比如收税，如果逃税被抓会被罚到破产，那就会降低逃税的欲望。

“The question about the value of information can also be turned around: what is the value (or cost) of having other players know your strategy? The answer, of course, depends on exactly what strategy you are using. If you are using an exploitable strategy, such as TIT FOR TWO TATS, the cost can be substantial. On the other hand, if you are using a strategy that is best met with complete cooperation, then you might be glad to have your strategy known to the other. For example, if you were using TIT FOR TAT, you would be happy to have the other player appreciate this fact and adapt to it, provided, of course, that the shadow of the future is large enough so that the best response is a nice strategy. In fact, as has been said, one of the advantages of TIT FOR TAT is that it is easy for it to be recognized in the course of a game even if the player using it has not yet established a reputation.”

当策略是有可以被剥削的时候，不让别人知道你的策略很重要，但一个策略如果是不能被剥削的，那就是“阳谋”，即使别人知道你下一步会怎么做，仍然得选择合作

“A government must deter its citizens from breaking the law. For example, to collect taxes effectively, a government must maintain a reputation for prosecuting tax evaders. The government often spends far more investigating and prosecuting evaders than it acquires from the penalties levied against them. The government’s goal, of course, is to maintain a reputation for catching and prosecuting evaders to deter anyone contemplating tax evasion in the future. And what is true for tax collection is also true for many forms of policing: the key to maintaining compliant behavior from the citizenry is that the government remains able and willing to devote resources far out of proportion to the stakes of the current issue in order to maintain its reputation for toughness.”

杀鸡儆猴的作用，有时候动用的资源和成本远大于收益，但为了预防大面积的背叛，还是有必要做的。就比如现在中国队立陶宛的策略。