OK…once and for all, the Just War Theory. My source is Charles Rice’s “The Winning Side.” (Rice is a jurisprudence professor at Notre Dame law school and relies heavily on Thomistic thought.) Here we go:
The theory of just war, formulated by St. Augustine and developed by St. Thomas Aquinas and others, involves two concepts. First is Just ad Bellum, determining when recourse to war is permissible. Second is Just in Bello, determining the principles governing the conduct of the just war once it has begun.
Jus ad Bellum
“In order for a war to be just,” wrote Aquinas, “three things are necessary. First, the authority of the sovereign by whose command the war is to be waged. For it is not the business of a private individual to declare war, because he can seek for redress of his rights from the tribunal of his superior. Moreover, it is not the business of a private individual to summon together the people, which has to be done in wartime…Secondly, a just cause is required, namely that those who are attacked should be attacked because they deserve it on account of some fault…Thirdly, it is necessary that the belligerents should have a rightful intention, so that they intend the advancement of good, or the avoidance of evil.” The Catholic bishops of the United States have specified the requirements for going to war:
- Just cause
- Competent authority
- Comparative justice, i.e., “Which side is sufficiently ‘right’ in a dispute, and are the values at stake critical enough to override the presumption against war?”
- Right intention. War must be intended only for reasons which constitute just cause and it must be waged with the goal of peace and reconciliation, 'including avoiding unnecessarily destructive acts or imposing unreasonable conditions (e.g., unconditional surrender).
- War must be the last resort.
- There must be a reasonable “probability of success.” The Bishops note that this criterion prevents “irrational resort of force or hopeless resistance when the outcome of either will clearly be disproportionate or futile. The determination includes a recognition that at times defense of key values, even against great odds, may be a ‘proportionate’ witness.”
- Proportionality, i.e., “the damage to be inflicted and the costs incurred by war must be proportionate to the good expected by taking up arms.”
These concepts were incorporated into the Catechsim which insists that “legitimate defense by military force” must be in response to grave and lasting damage inflicted by an aggressor, it must be the last resort, with reasonable prospects of success, and it must not cause greater evils than the evil to be eliminated.
Jus in Bello
The two criteria that govern Jus in Bello, the manner of conducting a war, are "proportionality and discrimination." Proportionality requires that the war itself must be for a proportionate good, and also that tactics and weapons used in that war must be proportionate to the situation. Discrimination "prohibits directly intended attacks on noncombatants and nonmilitary targets." "Every act of war" said the Second Vatican Council, "directed to the indiscriminate destruction of whole cities or vast areas with their inhabitants is a crime against God and man, which merits firm and unequivocal condemnation."
Note that the Second Vatican Council condemned acts of war "directed to the indiscriminate destruction of whole cities or vast areas with their inhabitants." Under the principle of double effect, it could be morally justified to attack a military target of sufficient importance even though the attacker knows, but does not intend, that innocent civilians in the vicinity will be killed. However, at some point one would have to conclude that the unintended loss of civilian lives is so disproportionate that the attack could not be rightly made. A further consideration is whether the risk of escalation to a nuclear war of total destruction is so great as to preclude any use of nuclear weapons. The risk of escalation is present in any conflict but would be especially acute if nuclear weapons were used.