Lazar: Necessity in Self-Defense and War

Seth Lazar (Australian National Univ. - Philosophy) has published Necessity in Self-Defense and War (Philosophy & Public Affairs, Vol. 40, no. 1, pp. 3–44, Winter 2012). Here's the introduction:

Philosophers generally agree that justified self-defense must meet four conditions. First, the defender must face an unjustified threat. Second, there must be some grounds to prefer the defender's interests to those of his target (“Attacker,” though in some cases that name is not apposite). Third, the force used must be proportionate to the threat averted: the threat must be of sufficient magnitude to justify that much force. And fourth, the force used must be necessary to avert the threat. Much has been written on the first three conditions, each of which is subject to widely varying interpretations. The necessity constraint, however, has been generally neglected.

This neglect would be less troubling if necessity were either immediately perspicuous, or peripheral to the ethics of self-defense. Unfortunately, closer examination proves the simple, pretheoretical account of necessity to be inadequate. And if defensive harm can be justified only if it is necessary, this constraint could hardly be more important. Nor is this only a problem in self-defense: necessity plays a crucial role in both popular and philosophical thinking about the ethics of war. We standardly think that, regardless of whether the other criteria for permissible harm in war are met, unless force is necessary to avert an unjustified threat, we should refrain. Indeed, for one prominent school of just war theorists, necessity underpins the principle of noncombatant immunity, perhaps the single most important moral constraint on the use of force in war. These philosophers think that permissible killing in war is identical to permissible killing in self- and other-defense, indeed, that justified wars reduce to justified acts of self- and other-defense. They argue that, even if the other conditions that would make noncombatants legitimate targets of lethal force were satisfied, since killing noncombatants will never satisfy the necessity constraint, they are immune from attack on those grounds alone.

The necessity constraint, then, is at the heart of the ethics of both self-defense and war, and yet we know little about it. This article seeks to remedy that defect. It proceeds in two stages: first, an analysis of the concept of necessity in self-defense (Sections II and III); second, an application of this analysis to war, looking at both its implications for just war theory (Section IV) and its application in the laws of war (Section V).