Preemptive war: what would Aquinas say?

War is among the most terrible of human realities. Yet Catholicism has never condemned all participation in war as morally impermissible. From the early Middle Ages to our own time, the church has consistently asserted that some evils or threats are so grave that they merit a vigorous armed response. "It is the other side's wrongdoing that compels the wise man to wage just wars," wrote Augustine, one of the earliest exponents of what is now termed "just-war theory."

The intense debate over the U.S. invasion of Iraq, in which prominent neoconservative Catholics such as Michael Novak and George Weigel used just-war arguments to defend U.S. actions, has put the just-war theory under renewed scrutiny. This has called attention to the ongoing debate among just-war theorists about the correct starting point for moral reflection on war. Some thinkers, such as James Childress and Richard Miller as well as the United States Conference of Catholic Bishops, maintain that moral reasoning about war should begin with the imperative "Do no harm." From this obligation, they argue, there derives a strong presumption against the use of force, a presumption that can be overridden only in very exceptional circumstances. By contrast, Rutgers scholar James Turner Johnson, Weigel, and others have argued for a more proactive stance. Moral thinking about war should begin, they say, with the duty of civic leadership to oppose grave wrongdoing. Its true starting point is a presumption against injustice.

On one side we have those who view participation in war as morally suspect. Military force should therefore be resorted to only in the most pressing circumstances. It should not be deemed part of the ordinary functioning of political leadership. Opponents of this view make the case that it dangerously underestimates the weight of evil in human affairs, hindering the ability of political leaders to counter it effectively. Significantly, these rival versions of just-war theory both appeal to Thomas Aquinas as a key source for their views.

Proponents of the "presumption against war" view maintain that Aquinas's concept of just war is modeled on his more basic idea of legitimate defense. Hence they infer that the only correct rationale for resort to armed force is the purely defensive posture of repelling attack. Other reasons for "recurring to the sword" must be rejected as tantamount to aggression. Likewise, they endorse Aquinas's admonition against being overly suspicious ("when a man, from slight indications, esteems another man's wickedness as certain"). Relying on mere suspicions and not hard fact, statesmen can be tempted to condone preemptive attack. Finally, support is sought in Aquinas for the claim that the violent nature of military combat renders such action a poor instrument for the prosecution of justice. The point is not so much that the resort to lethal force is inherently wrong. Rather, it is held that warfare by its very nature is inclined to excess, and that such excess has been significantly aggravated by the destructiveness of modern weapons. Thus soldiers, even those whose intentions are good, inevitably get caught up in a spiral of violence.

In sum, the "presumption against war" interpretation places most of its emphasis on the prudential aspects of just-war reasoning. Issues surrounding proportionality and last resort occupy center stage. Principled matters of right--which earlier thinkers had treated under the rubrics of just cause and legitimate authority--are deemed to have only a secondary importance.

Proponents of the more robust version of just-war theory maintain that Aquinas never sought to limit the resort to armed force to simple self-defense. He did in fact think that occasions may arise when offensive war is warranted--to regain things wrongly taken, to thwart and punish organized evildoing, or to protect innocents from harm. Not only self-defense against actual attack (second use of force), but even a first use of force (offensive war) may be justified when it is the most efficacious response to wrongdoing. It has been argued for example that the Allies would have had good reason to initiate hostilities against Nazi Germany in 1936, when (in flagrant violation of his treaty obligations) Hitler remilitarized the Rhineland. On this understanding (as articulated by thinkers such as Aquinas, Vitoria, Suarez, Grotius and others in the classical just-war tradition), the distinction between defensive and offensive force does not reduce to the distinction between just and unjust war. To the contrary, limiting force to strict defense would have the undesirable effect of paralyzing action in the face of an unjust status quo or a dangerous military threat. In this interpretation, just cause remains the paramount consideration. Matters of prudential concern (proportionality, last resort, and so forth) should be subordinated to deliberations about just cause.