Before launching an attack on Iran’s nuclear facilities, we must pause to reflect on whether such military action is morally justifiable. As heirs of the West, we Americans have the privilege of drawing upon a tradition of moral reflection on war that is at least 2000 years old. The greatest philosophers and theologians of our history have contributed to the "just war" theory, including Cicero, Ambrose, Augustine, Thomas Aquinas, Vitoria, and Suarez, and this tradition has been embraced by a broad consensus of theologians and moral theorists from many religious and secular backgrounds. Just war theory embodies two principal ideas: the sacredness of human life, and the impermissibility of “doing evil that good may come” (as St. Paul put it in Romans chapter 3).
For the sake of argument, I will assume in this essay the worst possible case: namely, that the Iranian government is intent on pursuing the creation of nuclear weapons, and that there is a significant likelihood that Iran would either use these weapons directly against the United States or Israel, or give them to hostile terrorist groups such as Hamas or Hezbollah. Since a good end, no matter how important, cannot justify evil means, we must look to the just war theory for guidance in discerning what means for self-defense are permissible.
Just war theory lays down seven criteria that must be met in order to justify the initiation of war—that is, the use of lethal force against the members of another society. Given our assumption of the worst-case scenario, the first condition of just war theory, just cause, is easily met, at least at first glance. Defense of innocent human life, whether in one’s own country or in that of an ally, provides a just cause for military action.
The second condition, proportionality, also poses no obstacle. The harm resulting from a tightly focused attack on Iran’s nuclear facilities would be far outweighed by the unimaginable scale of death and suffering resulting from an Iranian nuclear attack on an American or Israeli city.
The third condition, right intention, simply requires that the just cause be the real reason for the action, and not merely an excuse for hostile action motivated by malice. At first glance, this would also seem to be met in this case; however, closer examination reveals that right intention cannot be met unless the final four conditions are also satisfied.
The remaining four conditions deserve careful attention: comparative justice, competent authority, last resort, and probability of success. Comparative justice means that the nation initiating the war must be significantly less guilty in the relevant respects than is the prospective enemy. It is not sufficient to be more just as a whole: comparative justice refers to the morally relevant features of the enemy being used as the cause of war. To be sincerely intending to act for a just cause against a possible enemy, the enemy must not have an equally just cause of the same kind against one’s own nation, since one’s intention cannot be properly focused on rectifying an injustice on the part of another nation while harboring a similarly unjust intention on one’s own part. Thus, right intention requires comparative justice.
If the justification for the attack were simply Iran’s imminent possession of nuclear weapons, then clearly neither the United States nor Israel would be in a position of comparative justice, since both have nuclear weapons as well. Even if the cause for war were the likely use of Iranian nuclear weapons against innocent civilians, this situation is a murky one, since the United States is the one nation that has actually used nuclear weapons against an enemy and, in at least one case (Nagasaki), against a civilian population center with no significant military installations. In addition, the United States has never officially apologized for the nuclear attack on Japan nor disavowed the future use of its nuclear weapons in such an indiscriminate fashion. Until both the United States and Israel renounce such unjust use of nuclear weapons and make such institutional reforms as are needed to prevent it, we cannot claim that the comparative justice condition has been met.
I am not claiming that there is moral equivalency between America or Israel and Iran. Far from it. However, comparative justice has nothing to do with the overall moral fitness over another. In many cases of just war it would be impossible to make such a judgment. Rather, comparative justice concerns the rectitude of our intentions, as demonstrated by our holding ourselves to the same standard on the issue in question to which we hold the enemy.
The application of the last resort and the competent authority conditions are connected. War, even when there is a just cause, must always be the last resort, used only when all just and peaceful attempts to prevent aggression with an appropriate chance of success have failed. The necessity of competent authority follows necessarily, since only a sovereign state can engage in discussions and negotiations with the required credibility, and only a sovereign state can declare, prior to its attack, that a state of war exists.
Just war theory resolutely opposes any surprise attack, such as that of the Japanese on Pearl Harbor, precisely because such an unanticipated action can never be a last resort. Sneak attacks do not provide the prospective enemy with an ultimatum that it can meet and thereby avert the catastrophe of war. A just war against Iran, therefore, would have to be a declared war. Given the United States Constitution, it is the sole prerogative of the Congress to issue any ultimatum with a declared state of war among its threatened consequences. The president lacks the constitutional authority to issue such an ultimatum or declaration. There may be cases in which action must be taken swiftly, leaving no time for the Congress to convene and make its decision, but that is certainly not the case here, with at least several months before a decision to launch a war must be made. Consequently, no action (either by American or allied forces) authorized solely by the president can be just.
The condition of last resort does not rule out the permissibility of a preemptive strike against a potential enemy, so long as the enemy is committed in a practically irrevocable way to launching an unjust attack—that is, so long as the unjust attack is “imminent” in this narrow sense. However, it is hard to believe that an attack involving the use of nuclear weapons could truly be imminent before a single one of those weapons has actually been built. There are many steps that would have to be completed between Iran’s successful construction of nuclear weapons and their use. By the nature of human free will and the structure and pacing of decision-making, the Iranian leadership cannot already intend those steps in a concrete and specific form. Consequently, they are not yet unjust aggressors, and so not yet the legitimate target of defensive action.
Why is the condition of last resort so important, given that following this principle brings with it a significant risk of great harm? Last resort matters because when we go to war prematurely, we cannot act with the right intention. If war is something other than our last resort, we reveal our unjust disregard of the humanity of our enemies. The only justification for killing a human being (outside of capital punishment) is to prevent that person’s participation in some unjust killing of another, and to do so only after they have formed the firm intention to kill. When we kill prematurely, we allow other considerations to weigh against the value of their lives, and we deny the inherent dignity of our enemies when we anticipate evil intentions that they have not yet formed. I cannot legitimately shoot someone now in self-defense, simply because, given his wicked disposition, he will almost certainly intend to kill me at some time in the future.
Finally, a just war must bring with it a reasonable probability of success. Because of Iran’s anticipation of an American or Israeli attack on its facilities, it has hardened the sites to an extraordinary, perhaps even unprecedented, extent. Even if an attack were entirely successful at destroying one or more critical sites, the most that could be reasonably hoped for is to delay Iran’s acquisition of nuclear weapons for a few years. Wouldn’t such a delay count as a “success”? It’s true that we could be justified in thwarting an imminent attack now, even if doing so wouldn’t prevent all future acts of aggression. However, in this case, there is no specific attack that we would be thwarting: we would be merely postponing the acquisition of the means for an attack, and such mere postponement cannot justify the intentional killing of Iranians. It may be that a prolonged and massive air assault would increase the probability of success, and thereby be more defensible than a limited campaign, but plans for such an all-out campaign would call for even more stringent examination on the grounds of proportionality, as well as evaluation of the American people’s willingness to see such a massive effort through to its conclusion.
Furthermore, it is quite possible that an attack or the threat of an attack would actually accelerate the Iranians’ pursuit of nuclear weapons, since they would reasonably conclude that only by actually possessing such weapons could they (like North Korea) deter America and Israel from attacking. Without a reasonable probability of success at preventing the development of an Iranian bomb, an attack on their facilities could not be carried out with the right intention, even if the cause is just. It would merely be an act of frustration and anger, not genuinely ordered to the defense of innocent life.
It might be objected that the usual rules of just warfare do not apply to the United States, since we are (as the world’s only superpower) the de facto “policeman of the world.” However, this is irrelevant to the issue at hand, since even police officers are morally bound by principles exactly like those of the just war theory: a police officer may not rightly use lethal force without satisfying just cause, right intention, comparative justice, last resort and the other conditions. Just war theory applies even to global policemen.
One might also argue that the just war criteria are irrelevant, since we are intending merely to destroy Iran’s facilities (reactors and centrifuges), with the deaths of Iranian workers merely a foreseen but unintended consequence (appealing to the doctrine of “double effect”). However, the doctrine does not apply in this case: the presence of workers and scientists is a normal facet of the operations of these facilities, and so killing them is an integral part of the centers’ destruction, making the killings “intentional” in the relevant sense.
Just war theory, therefore, clearly directs us to reject the claim that the Iranian nuclear program provides either America or Israel with moral grounds for an attack at this time on Iran’s facilities or scientists, since such an attack would be undeclared and premature, since it would have insufficient probability of success, and since neither America nor Israel can claim comparative justice in respect of the possession of nuclear weapons. A war must be justified in terms of acts of aggression that Iran has already committed or is about to commit, not in terms of what it might do in the future. In deciding whether to go to war with Iran, we must focus instead on Iran’s involvement in unjust aggression against Israel on the part of Hamas (al-Qassam Brigades), Hezbollah, Palestinian Islamic Jihad, and the al-Aqsa Martyrs’ Brigades and other Iranian proxies.
We can apply the same seven criteria to a hypothetical response by either Israel or the United States (acting on behalf of its ally) to this indirect aggression by Iran. The just cause condition is met by Israel’s right to self-defense. Comparative justice favors the Israelis, given the indiscriminate nature of the attacks and the deliberate targeting of non-combatants by Iran’s regional proxies. Any response to this aggression, however, must be proportional to the actual harm suffered and the harm truly imminent (in the strict sense). A quick, surgical strike against nuclear facilities might satisfy this proportionality constraint, but a large-scale, sustained air campaign by the United States Air Force would involve violence on a far greater scale than has been suffered by Israel.
In addition, any such response to Iran’s support of terrorism would still have to be a last resort. A formal declaration of the intent to wage war on the part of the Senate, along with a specific set of demands, must precede any U.S. military action. Iran must be given the opportunity to avoid war by ending its support of terroristic and other unjust aggression against Israel, and by recognizing Israel’s right to exist and right to a peaceful, negotiated settlement of the rights of Palestinians.
If these conclusions are correct, then it would be wrong, not only for the United States to engage at this time in an attack on Iran, but also for it to participate substantially in an Israeli action (by knowingly providing the aid, arms, or technical support required, whether overtly or covertly). In addition, if it would be unjust to attack Iran on the grounds of its nuclear program, it would also be unjust even to threaten to attack on those same grounds. This is, admittedly, a difficult conclusion to embrace, given the very real risks involved in taking military action “off the table,” but we must assiduously seek to do justice and trust the results to Divine Providence.
Robert C. Koons is professor of philosophy at the University of Texas at Austin. He is a senior fellow of the Witherspoon Institute and sits on the editorial board of Public Discourse.