On top of that, there is new potential for poisoning the soil, the atmosphere, and the genetic endowments of plants, animals, and humans with radioactive and other toxic materials. Given these developments, many ask if a just war is even possible. That’s a question to be taken very seriously.

Just thinking about it, by the way, throws new light on the importance of diplomacy as a means of avoiding war.

Remember we all live under a commandment to love our neighbor. How do we remain faithful to that commandment when confronted with the reality of war?

The moral theory of the "Just War" or "limited war" doctrine begins with the presumption that all Christians are bound to do no harm to their neighbor and to love their neighbor. So in their 1983 pastoral letter on War and Peace, the Catholic bishops of the United States asked: “How is it possible to move from these presumptions to the idea of a justifiable use of lethal force?”

And here is their answer: “Historically and theologically the clearest answer to the question is found in St. Augustine. Augustine was impressed by the fact and the consequences of sin in history—the ‘not yet’ dimension of the kingdom. In his view, war was both the result of sin and a tragic remedy for sin in the life of political societies. . . .Faced with the fact of attack on the innocent, the presumption that we do no harm, even to our enemy, yielded to the command of love understood as the need to restrain an enemy who would injure the innocent,” the bishops said.

Over time, this Augustinian premise developed into a Catholic doctrine of a right of self defense and the right was parsed, if you will, or translated into a set of criteria for the exercise of that right of self defense.

The Just War theory evolved in an effort to prevent war. Only if war cannot be avoided do these criteria come into play. The presumption is in favor of peace and against war. The tradition looks at war as clearly a last resort. So it is no surprise that the first of these so-called "Just War" criteria--the set of conditions that must be met if the decision to go to war is morally permissible--should be a “just cause.” There must be good reason, a just cause, for going to war.

Chief among the several other criteria (I won't list them all here) is one called “proportionality.” This means that the damage to be inflicted and the costs incurred by war must be proportionate to the positive outcome that is expected to result from the armed conflict. In today’s interdependent world, even a local conflict can affect people everywhere; this is particularly the case when nuclear weapons are involved.

A nation cannot justify going to war without considering the effect of its actions on itself as well as on others in the international community.

There is also a principle of “discrimination.” This principle tries to protect the immunity of non-combatants. Do weapons discriminate? Are they selective in the sense that they avoid hitting civilians—women and children, as we say?

Applying all of this to Iraq, which, I'm convinced, is an unnecessary war, I have to conclude that it is also an unjust war. We should turn away from war now and rely on diplomacy as the only way to peace in the Middle East.