The release in late May of Pope Leo’s new encyclical, “Magnifica Humanitas,” occasioned significant public interest because of the document’s focus on artificial intelligence and its impact on human life. But so too did other issues raised in the encyclical, including the viability of the Catholic Church’s venerable just war theory.
Ever since the United States and Israel initiated “Operation Epic Fury” against Iran on Feb. 28, we had already witnessed a resurgence of discussion of just war theory. I have read over 100 articles, opinion pieces and interviews during this time in which just war criteria were used either to criticize or to justify the war—from theologians, philosophers, ethicists, politicians and pundits to priests, bishops, archbishops and Vatican officials.
Some politicians—like President Donald J. Trump, White House adviser Stephen Miller and Secretary of Defense Pete Hegseth—have made no pretense about respecting or adhering to just war principles, the international laws of war and rules of engagement. However, both Vice President JD Vance and Speaker of the House Mike Johnson have mentioned just war theory—although without attending to its principles—in response to remarks by Pope Leo XIV that God is “never on the side of those who yesterday wielded the sword and today launch bombs.”
“Magnifica Humanitas” asked a different question, however. Is just war theory still relevant? One sentence in paragraph 192 of the encyclical drew inordinate attention: “Today, more than ever, without prejudice to the right to self-defense in the strictest sense, it is important to reaffirm that the ‘just war’ theory, which has all too often been used to justify any kind of war, is now outdated.” Just this past weekend, Pope Leo also told journalists that “the just war theory comes from centuries past when we couldn’t imagine the weapons [and] human beings’ ability for destruction.”
One journalist has written that the pope has “repudiated” and “disavowed” just war theory. And my friend Justin Bronson Barringer, a Protestant ethicist and pacifist, asked on social media: “Did the Pope just make Catholics pacifist?”
The encyclical and the aftermath
The short answer to his question is “no,” but it is necessary to provide, as they say here in Ireland, a proper response.
When Pope Leo notes in “Magnifica Humanitas” “the right to self-defense in the strictest sense,” we see the obvious evidence that he still recognizes what the Catechism refers to as “the strict conditions for legitimate defense,” which are “are the traditional elements enumerated in what is called the ‘just war’ doctrine” (No. 2309). These criteria include just cause, last resort, proportionality, the probability of success, legitimate authority and noncombatant immunity, with right intent implied under the heading of “safeguarding peace.”
A major concern in this section of the encyclical is the “normalization of war” (Nos. 189-192). Pope Leo writes, “When historical memory fades and the ethical principles that protect civilians and the most vulnerable are weakened, it becomes easier to justify violence as necessary, inevitable or even ‘sanitized’” (No. 192). Two paragraphs earlier, he similarly observes, “Today, however, we are witnessing a real paradigm shift in public discourse and in decisions regarding rearmament, with a troubling revival of war as an instrument of international politics, while the very ethical principles that had previously limited its use are being eroded” (No. 190).
Yet it is important to remember a point the Jesuit theologian John Courtney Murray noted about the violations of just war principles during the Second World War: “This is no argument against the traditional doctrine. The Ten Commandments do not lose their imperative relevance by reason of the fact that they are violated.” Rather than saying the ethical criteria of just war theory are outdated, the answer is to emphasize their proper use, and to teach the just war doctrine more rigorously as well as to clearly expect more stringent adherence to it.
With it, though, Pope Leo still recognizes what the Catechism refers to as “the strict conditions for legitimate defense,” which are “are the traditional elements enumerated in what is called the ‘just war’ doctrine” (No. 2309). These criteria include just cause, last resort, proportionality, the probability of success, legitimate authority and noncombatant immunity, with right intent implied under the heading of “safeguarding peace.” With the word “reaffirm,” Leo has in mind Pope Francis’ encyclical “Fratelli Tutti,” which asserted “it is very difficult nowadays to invoke the rational criteria elaborated in earlier centuries to speak of the possibility of a ‘just war’” (No. 258). Both popes make this claim in the face of the increasing destructiveness of modern technology and the susceptibility of just war to be “used to justify any kind of war” by the powerful.
Alternatives and nuances
To be sure, Leo rightly notes that the “Church’s Social Doctrine is not the result of a project devised at a desk” (No. 45) but instead is a dynamic “process of shared discernment” (No. 27) with the human sciences, other Christian denominations and non-Christian religions, and especially the perspective of the vulnerable and the victims of violence. This is not to say that principles and criteria are unnecessary at all. Indeed, the encyclical mentions “principles” over 70 times and “criteria” nearly 30 times.
Even if they are insufficient, the pope maintains that “the Social Doctrine of the Church is a legacy of wisdom, where we find principles for thought, criteria for discernment and judgment, and concrete guidelines for action” (No. 3). While he highlights the inalienable dignity of the human person, the common good, justice and more, I would add that the criteria of just war theory are meant to satisfy justice and to protect innocent persons and the common good.
As the philosopher Gregory Reichberg notes, “Magnifica Humanitas” actually uses just war criteria itself. On artificial intelligence and weapons, Leo writes, “It is not enough to invoke a generic type of ethics. Concrete criteria for discernment must be established” (No. 199). One criterion the pope employs is noncombatant immunity, which is also known as the principle of discrimination (or distinction): “Target selection and the use of force must not confuse combatants and non-combatants, nor ignore the impact on defenseless populations” (No. 199).
Similarly, Leo observes that autonomous weapons systems, which are “less subject to human control,” violate “the principle that armed force should be used only as a last resort in cases of legitimate self-defense” (No. 197). In addition, he alludes to “the principle of proportionality in responding to aggression” (No. 203) and the “extremely high human and environmental costs” of war (No. 195).
Interestingly, there is no explicit reference to pacifism or nonviolence in the encyclical. In an implicit use of the criterion of probability of success, Pope Leo writes, “Humanity possesses far more effective and capable tools for promoting human life and resolving conflicts, such as dialogue, diplomacy and forgiveness” (No. 192). The emphasis on peacebuilding, diplomacy, conflict prevention and international law (No. 203) also helps render armed force truly a last resort. Still, ever since his first “Urbi et Orbi” blessing at Easter a year ago, Leo has frequently used “the expression ‘to disarm,’ which is close to my heart” (No. 110). While this may sound like nonviolence or pacifism, I don’t think this is what the expression means.
After all, St. John Paul II, in his 2000 World Day of Peace message, wrote in regard to humanitarian intervention in cases of genocide and crimes against humanity: “Clearly, when a civilian population risks being overcome by the attacks of an unjust aggressor and political efforts and non-violent defense prove to be of no avail, it is legitimate and even obligatory to take concrete measures to disarm the aggressor,” a point that was echoed in the Compendium of the Social Doctrine of the Church (No. 506). In 2014, on the question of what should be done about the genocidal violence of ISIS against ethnic and religious minorities in northern Iraq, Archbishop Silvano Tomasi said that “when all other means have been exhausted, to save human beings the international community must act. This can include disarming the aggressor.”
For his part, instead of “disarming,” Pope Francis said, “In these cases where there is unjust aggression, I can only say that it is licit to stop the unjust aggressor. I underscore the verb ‘stop’; I don’t say bomb, make war—stop him.” He added, “The means by which he may be stopped should be evaluated,” and he expressed his concern that “powerful nations” abuse this rationale of “stopping an unjust aggressor” for ulterior motives, such as conquest.
Of course, as Leo says of Catholic social doctrine (and I would include here just war doctrine), “It is not a handbook of principles and norms to be applied, but a process of shared discernment” (No. 27). It includes “adopting to the perspective of victims” and listening to their stories (No. 216).
Rethinking just war and the use of force
The question of the use of force has not only been an academic one for me, but something I initially wrestled with when I worked for several years in law enforcement. As a working-class, first-generation college student, moreover, I was in Army R.O.T.C. and trained briefly at Fort Benning, Ga. I have seen what violence can do to others; I have been on the receiving end of violence myself; and I have used force to defend myself and others.
Although I later studied in graduate school under two of the United States’ most prominent pacifist theologians—Stanley Hauerwas and John Howard Yoder—I believe that the use of force is sometimes justified. I also try to listen to my students from Ukraine, Nigeria and other war-torn nations who know the suffering from violence firsthand and who think there is still a place, sadly, for just war theory.
As I and others have observed, there are rival versions of just war theories, ranging from the dovish to the hawkish, within the just war tradition. Likewise, there are a variety of pacifisms and approaches to nonviolence. Getting a better grasp of these terms might help interlocutors avoid talking past each other or oversimplifying matters as just war versus pacifism.
In his 2008 book, Peace: A History of Movements and Ideas, the peace scholar and activist David Cortright observes that the word “pacifism” at the beginning of the 20th century was “a general term to describe the stance of those opposed to war.” It included a “purist position” of “absolute pacifism” that refused to condone or participate in any war whatsoever, as well as the more widely accepted “pragmatic or conditional pacifism,” which opposed war in principle while “accepting the possibility of using force for self-defense or the protection of the vulnerable.”
Those in the latter group who also “believe that war can be prevented and with sufficient commitment to justice can be abolished, or nearly so,” were sometimes called “pacificists” rather than “pacifists.” Without retaining the term, Cortright thinks it can “help to bridge the gap” between pacifism and just war theory by providing “a more holistic framework for understanding peace advocacy,” especially given that the “majority of those who work for peace seek to avoid war but are willing to accept some limited use of force for self-defense or to uphold justice and protect the innocent.”
This, rather than pacifism or even just war, more accurately describes the current position of Pope Leo and the Catholic Church. While I wholeheartedly agree that nonviolence should be centralized, prioritized and taught more so that it is our starting point and default stance, just war theory as a mode of moral reasoning with its criteria concerning the use of force, remains relevant even if its application to new technologies and geo-political developments always needs to be updated.
Indeed, prior to “Magnifica Humanitas,” ethicists have already been employing just war theory to tackle problems raised by A.I., including in the recently published book, Just War Theory and Artificial Intelligence: Challenges and Consequences, edited by Maria Power and Maggi Savin-Baden.
According to the British Catholic theologian Anna Rowlands, who participated in the Vatican presentation of the encyclical, “Magnifica Humanitas” “doesn’t completely repudiate” just war theory. Instead, Rowlands suggests, “It is a strong statement about the need for [just war theory] to be placed in a renewed wider context of criteria for building peace and resolving conflict.”
Nearly five decades ago, the political scientist Francis A. Beer distinguished between “polemology,” which is the study of war, and “paxology or peace science, the study of peace.” Although I have previously suggested in America and elsewhere that we use the phrase “integral peace” as a way to synthesize nonviolence and just war theory, perhaps a better name would be “integral paxology” to mirror Pope Francis’s call in “Laudato Si’” for “integral ecology.”
May I suggest that such an approach be developed in an upcoming apostolic exhortation or World Day of Peace message?
Politics
Faith
Culture
Vatican
Scripture
Podcasts