Has natural selection designed human beings to cooperate? Can selfishness really be more ‘rational’ than cooperation? Ken and John ask us to consider a thought experiment (credited to Hume) where two neighboring farmers, Ethan and Duncan, each have to plow their fields. Ethan suggests that he help Duncan plow his field today, then Duncan can help Ethan the next day. But, as John points out, is it reallyrationalfor Duncan to help Ethan the next day, after his own field has already been plowed? In the cost-benefit analysis, Duncan does not get any benefit from taking on the cost of helping Ethan. This situation is modeled by game theorists as the “Prisoner’s Dilemma,” where two players must cooperate to achieve the group-optimal solution, although each individually rationally benefits from choosing to not cooperate. Cristina Bicchieri, an expert on ‘fairness’ in game theory, joins Ken and John to discuss the philosophical puzzle of cooperation versus conflict.

为什么博弈论是如此强大的工具?Cristina将博弈论描述为“描述互动情境的简单方法”。在我们的世界中，选择往往是相互依赖的，它们取决于我们对别人将如何做出选择的预期。克里斯蒂娜认为，像“靠右行驶”这样的社会习俗可以从博弈论提供的模型中受益。

Cristina argues that what drives apparently rational agents is their belief in the ‘norm’ of fairness, as well as their belief that other agents will act according to that norm. An astute listener (Lee) asks our hosts to fully define what they mean by fairness. Cristina offers what she considers the three standard definitions: dividing equally, according to need, or according to deserved merit. Of course she readily admits that these three definitions often come into conflict. Do the Wall Street ‘one-percenters’ really deserve their unequal share? How much charity is fair to those below the poverty line?

John points out that we may be motivated to cooperate regardless of what we consider to be fair. After all, he says, if Ethan and Duncan are married it may definitely be in Duncan’s best interests to plow Ethan’s field, if only so that he will be able to sleep in peace. These issues and more are explored in depth, and Cristina argues that we are ‘hard-wired’ to understand norms of fairness but not to cooperate unconditionally, and these fairness preferences can be successfully preserved in a game-theoretic framework. Thus our rationality is preserved in the face of selfishness’ short-term allure.

• Roving Philosophical Reporter (seek to 5:30):Caitlin Esch explores the Prisoner’s Dilemma as it arises in ‘real-life’ scenarios. In the cancelled British game showGolden Balls, in which players compete to win a pool of money, then must eventually choose whether to ‘split’ or ‘steal’ against their competitor. If both split, then they each walk home with half the money. If they both steal, neither get anything. But if one splits and one steals, the stealer gets the entirety of the money. This situation perfectly captures the essence of the Prisoner’s Dilemma.

• 60-Second Philosopher (seek to 49:00):Ian Shoales reminds us that cooperation often appears in unpopular ways, from kindergarten teachers to corporate teamwork building exercises. After all, he says, there may be no ‘I’ in “team,” but there is most certainly a ‘u’ in “suck.”