Why Just War Theory Always Matters

The claim that ‘there is no just thing as a just war’ is dangerous nonsense.

USS Gerald R. Ford (CVN-78), foreground, alongside USS Harry S. Truman (CVN-75), rear, in 2020.
USS Gerald R. Ford (CVN-78), foreground, alongside USS Harry S. Truman (CVN-75), rear, in 2020. (photo: US Navy / Public Domain)

Last month, I had the honor of addressing the Civitas Dei Fellowship, which is sponsored by the Dominicans’ Thomistic Institute in partnership with Catholic University’s Institute for Human Ecology. By the time I spoke at the closing banquet, several dozen students had spent an intense three days wrestling with the just war tradition, debating texts by just war classicists like Augustine and Thomas Aquinas and contemporary just war theorists like Gregory Reichberg of the Oslo Peace Research Institute. After that heavy dose of seriousness, a little light relief might have been in order.

But given our perilous times, I hoped the students wouldn’t mind that, instead of the usual post-dinner jokes and anecdotes, I tried to bring their intense reading and discussion into play with some very real 21st-century issues. I’ll summarize them telegraphically here, because these issues are most certainly Not For Scholars Only.

The just war way of thinking has been displaced by a “functional pacifism” in most Christian churches today, at least among church leaders.

This is not the result of a moral commitment to classic pacifism (which holds that war is intrinsically evil and that refusal to participate in lethal violence is a Gospel imperative) but to various forms of ecclesiastical wokery. The net result of the churches’ concessions to the political left has been to take religious leaders out of serious conversation with policymakers on matters of war and peace, leaving them to lob minatory rhetorical grenades from the bleachers.

The claim that “there is no just thing as a just war” is dangerous nonsense.

The claim is dangerous theologically, because the just war way of thinking is based on the natural moral law, the truths built into the world and into us that we can know by reason. The truths of the natural moral law are true perennially and are not changed by political or technological circumstances, although the implications of those truths will evolve over time.

The claim is dangerous pastorally because to argue that there can be no “just war” today is another way of saying that contemporary warfare is intrinsically evil. And to say that is to place an unwarranted burden of conscience on serious Catholics in the armed forces — which, in the American case, means a far higher percentage of Catholics than are found in the general population.

The claim also makes religious leaders look incoherent (at best) when, on the one hand, they praise men and women in the military for their patriotism and self-sacrifice and, on the other hand, declare a “just war” impossible.

The obvious example of a just war today is Ukraine’s war for national survival against Russian aggression; Russia’s war, by contrast, is unjust in both its intention and its conduct.

The just war way of thinking does not begin with a “presumption against war.”

Aquinas didn’t think so and neither should we. The “presumption against war” starting point smuggles a pacifist premise into just war theory, which then turns just war thinking into a series of hoops for political leaders to jump through. Rather, the just war way of thinking begins with rightly constituted political authority’s responsibility to provide for the security of those for whom public officials have assumed responsibility. That is why a just war is the use of military force in defense or promotion of the common good, which is one of the ends or purposes of politics. Clausewitz may have been wrong about some things, but he was right when he said that war is an extension of politics by other means. If war isn’t that, it’s mindless slaughter.

So if the just war way of thinking isn’t a serious of tests that ethicists and religious leaders pose for political leaders, what is it?

Just war theory provides a framework for collaborative reflection by ethicists, religious leaders, diplomats, and public officials in thinking through the hard problems of securing the peace of order — the peace composed of justice, security, and freedom — in a disordered world: which is this world, this side of the Kingdom come in glory. That reflection addresses how the proportionate and discriminate use of armed force can be directed to the peace of order. So in addition to the classic just war criteria — the ius ad bellum or “war-decision law,” and the ius in bello or “war-conduct law” — a developed just war way of thinking contains a ius ad pacem: reflection on the restoration or creation of peace.

And that ius ad pacem ought not be confused with contemporary “just peace” theory, which is another form of functional pacifism, its name parasitical on the just war principles it eviscerates.