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Self-defensive war uses violence to transfer risks from one’s own people to others. We argue that central questions in just war theory may fruitfully be analyzed as issues about the morality of risk transfer. That includes the jus ex bello question of when states are required to accept a ceasefire in an otherwise-just war. In particular, a “war on terror” that ups the risks to outsiders cannot continue until the risk of terrorism has been reduced to zero or near zero. Some degree of security risk is inevitable when coexisting with others in the international community, just as citizens within a state must accept some ineradicable degree of crime as a fact of community life.

We define a conception of morally legitimate bearable risk by contrasting it with two alternatives, and argue that states must stop fighting when they have achieved that level. We call this requirement the Principle of Just Management of Military Risk. We also argue that states should avoid exaggerated emphasis on security risks over equivalent risks from other sources—the Principle of Minimum Consistency Toward Risks. This latter principle is not a moral requirement. Rather, it is a heuristic intended to correct against well-known fallacies of risk perception that may lead states to overemphasize security risks and wrongly export the costs of their security onto others. In conclusion, we suggest that states must invest in non-violent defensive means as a precondition for legitimately using force externally.

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Ethics (forthcoming)