Just War Theory

A tradition of Western, mainly Christian ethical reflection that articulates conditions under which the state's engaging in armed conflict might be judged the right thing to do. The considered tradition never confuses this with judging war a good thing. Saint Augustine of Hippo, authoritative precursor for the medieval thinkers who developed a more systematic [Page 791]approach, believed war at best to be an unhappy necessity. In a world fundamentally disordered by human sin, a war that limited the effects of that disorder might be just.

The medieval systematizers, followed by the great Humanist jurists, developed two sets of criteria. The first set, ius ad bellum, suggests usually six conditions for testing a decision to go to war. They are (1) that the cause invoked is just (traditionally, only self-defense against prior aggression qualifies, though strong arguments have been made to include assisting victims of aggression, as regarding NATO's intervention against Serbia in former Yugoslavia), (2) that the party declaring war has legitimate authority to do so, (3) that the party intends only to halt aggression and secure peace, (4) that war is only entered upon as a last resort, (5) that victory—and peace—is a likely outcome, and (6) proportionality, such that the right secured by fighting outweighs the wrong which making war inevitably entails.

The second set of criteria, ius in bello, addresses justifiable conduct in warfare: (1) there should be discrimination between combatants, who may be attacked, and noncombatants, who should be immune; (2) when noncombatants are injured or killed, it may be excused provided it was not intended (the principle of “double effect”); and (3) there should be proportionality in any particular act of war.

Some critics of just war reasoning argue that the mere suggestion of the possibility of a war being justified plays into the hands of warmongers, who will claim that “threats to the state” require shooting first and asking questions later. Worse, modern warfare, whether waged with nuclear or conventional weapons, is so indiscriminate in its carnage, and so disproportionate to any imaginable offense, that just war conditions simply no longer touch reality.

For Augustine and those living in medieval times, the crucial issue of right was tied to a theological doctrine of sin. There was a particularly rigorous expectation, admittedly in light of an ideal, that all conditions must be met for a war to be deemed just. If the theological background has become less formative, nevertheless the just war tradition continues to be influential—witness the international controversy over justifications offered for the 2003 U.S.-led invasion of Iraq. International law of war, such as the Geneva Conventions, is significantly influenced by just war criteria. Recent thinkers have proposed a third set of conditions, ius post bellum, reflecting a more modern point of view that peace is not the natural state of society, which just war restores, but rather that belligerents have an obligation to build peace in the wake of war. Furthermore, important resonances with religions besides Christianity have been discovered, creating a greater community to which just war thinking must answer.

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