Abstract Is the world better off with nuclear weapons or without? Nuclear pessimists point to the potentially devastating costs of a nuclear war. Nuclear optimists argue that nuclear weapons reduce the likelihood of war and are thus beneficial. This debate is inconclusive in part because it misses an important conceptual point. We should care both about the cost of war and the likelihood of war, as they combine to form the expected cost of war, which is the product of the two. I discuss five implications of focusing on expected costs. Three support the pessimists: (1) nuclear weapons raise the upper limit on how destructive wars can be; (2) there may be a floor on how low the likelihood of war can go; and (3) risk aversion over damage will raise the expected cost of nuclear war. The remaining two support the optimists: (4) strategic models exhibit a declining expected cost of war; and (5) casualty data show that the expected cost of war is declining over its observed range in the past two hundred years.

中文翻译：

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坚强的孩子与达摩克利斯之剑：核武器和战争的预期成本

摘要 有核武器还是没有核武器世界会更好？核悲观主义者指出核战争的潜在破坏性成本。核乐观主义者认为，核武器降低了战争的可能性，因此是有益的。这场辩论没有定论，部分原因是它错过了一个重要的概念点。我们既要关心战争的成本，又要关心战争的可能性，因为它们结合起来就形成了预期的战争成本，是两者的乘积。我讨论了关注预期成本的五个含义。三人支持悲观主义者：（1）核武器提高了战争破坏性的上限；(2) 战争发生的可能性有多低可能有下限；(3) 对损害的风险规避会提高核战争的预期成本。剩下的两个支持乐观主义者：(4) 战略模型显示战争预期成本下降；(5) 伤亡数据显示，在过去 200 年的观测范围内，战争的预期成本正在下降。