A Journal of Philosophy, Applied to the Real World


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Jeff McMahan raises some valid concerns about the paper, and I am grateful both for his taking the time to do so, and for the opportunity to clarify my central argument. Rather than attempt a blow-by-blow defence, I’ll just concentrate on three major points, before summing up.

I elliptically misattributed to McMahan the Walzerian view that intentional killing in war is justified only when the target is liable to be killed. However, throughout McMahan’s work (until recently) the role of lesser evil justification has been radically circumscribed, confined to situations where intentionally killing the nonliable is necessary to avert an unusual catastrophe, of the sort that justified war does not typically aim to avert (of course Walzer too thought intentionally killing the nonliable permissible in supreme emergencies). Throughout his oeuvre, McMahan has argued that most combatants on the unjust side are sufficiently responsible for unjustified threats to be liable to be killed. I intended to target this thesis. In ordinary wars (which are not fought to avert supreme emergencies) many combatants who are intentionally killed are not liable to be killed, so if killing is justified, it is as a lesser evil. Since we do think that wars can sometimes be justified, even if not to avert an unusual catastrophe, this suggests that lesser evil justification must play a greater role in just war theory than Walzer, and until recently McMahan have thought. McMahan’s recent move towards a similar view is a welcome evolution, but an evolution nonetheless.

Seth Lazar’s “Associative Duties and the Ethics of Killing in War” is an original, rich, challenging, and intricately argued contribution to our understanding of the ethics of war. Its main aim is to explain how fighting in a war can be permissible when warfare inevitably involves the killing of people who are not liable to be killed—a problem that is more extensive than it may seem.

Civilians are almost inevitably killed in war and Lazar accepts that few if any civilians are liable to be killed in war. In principle, of course, a war could be fought without killing civilians, and certainly without killing them intentionally. Yet it is scarcely possible to fight a war, or at least a war in the familiar sense, without intending to kill enemy combatants. Lazar believes, however, that many combatants are not liable to be killed. As I and others have argued, those who fight for a just cause in a just war (“just combatants”), and by permissible means, do nothing to make themselves morally liable to be killed—that is, they do nothing to forfeit or lose their right not to be killed. And Lazar himself has argued, in previous work, that many combatants who fight in wars that lack a just cause (“unjust combatants”) are also not liable to be killed. This is because the harm that, as individuals, they threaten to cause is insufficiently great or because the degree to which they are responsible for the harm they threaten is too low. I think he is right about this, though I think the proportion of unjust combatants who are not liable to be killed is in most cases lower than he thinks it is.