Pope Leo: Just war theory is outdated

by Johnny Zokovitch

I think it is fair to say that Pope Leo XIV’s recent encyclical, Magnifica Humanitas (On safeguarding the human person in the time of artificial intelligence) has everyone talking. The encyclical could not have been more timely, dropping into the midst of graduating college seniors booing commencement speakers’ praise of artificial intelligence and the US government’s contrary efforts to both reign it in and expand its use–particularly in service of the Pentagon’s agenda. 

But one line particularly moved the needle for Catholics who for decades have been debating the Church’s teaching on war and peace. 

“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important to reaffirm that the ‘just war’ theory, which has all too often been used to justify any kind of war, is now outdated,” wrote Pope Leo in paragraph 192. 

(Insert here whatever meme you use to express “mind blown.”)

Even as Church teaching on war and peace has evolved rapidly (at least for an institution 2,000 years old not known for changing quickly), US Catholic bishops, theologians, ethicists and commentators–when faced with US military campaigns–would still most often default to critiques that employed the just war theory, first articulated by St. Augustine in the 4th century and further developed over centuries.

But the just war theory has been on life support for a long-time now.

Beginning with Pope John XXIII’s encyclical, Pacem in Terris, we hear the first tentative acknowledgement that the tool which the church has used for so long is no longer suited for the times in which we find ourselves.

“Men (sic) nowadays are becoming more and more convinced that any disputes which may arise between nations must be resolved by negotiation and agreement, and not by recourse to arms. We acknowledge that this conviction owes its origin chiefly to the terrifying destructive force of modern weapons. It arises from fear of the ghastly and catastrophic consequences of their use. Thus, in this age which boasts of its atomic power, it no longer makes sense to maintain that war is a fit instrument with which to repair the violation of justice.” (126-127)

Bishops’ conferences around the world, including the US bishops, would pick up this thread (most notably in 1983’s The Challenge of Peace and the ten year anniversary document, The Harvest of Justice is Sown in Peace in 1993), weaving alternative frameworks and not relying solely on just war theory in reflecting on the challenge of ongoing warfare when the means for humanity’s destruction were ever present.

In 2003 in a powerful and meticulous article in America, Drew Christiansen SJ explored the fate of just war theory and argued that what we were beginning to see was a “hybrid Catholic position” that embraced theories and practices rooted in gospel nonviolence.

“Prior to Sept. 11, 2001, official Catholic teaching on the Just War had already evolved as a composite of nonviolent and just-war elements. This was a departure from post-Reformation Catholicism, when the Just War alone was the formal Catholic stance. The change, which had begun at Vatican II, accelerated as a result of the successful nonviolent revolutions in Eastern Europe that brought an end to Communist rule in 1989. Reflecting on those events in his 1991 encyclical Centesimus Annus, Pope John Paul II offered praise for the nonviolent activists who toppled the Communist regimes that had ruled Eastern Europe and voiced his opposition to war as a means for resolving conflict.”

Even when employing just war theory, for instance in opposition to the US-led first Iraq War, Pope John Paul II emphasized the “presumption against war,” imploring all of humanity, “War never again!” 

The most immediate groundwork for Pope Leo’s assertion that the just war theory is outdated was laid by Pope Francis in Fratelli Tutti, paragraph 258. 

“At issue is whether the development of nuclear, chemical and biological weapons, and the enormous and growing possibilities offered by new technologies, have granted war an uncontrollable destructive power over great numbers of innocent civilians. The truth is that ‘never has humanity had such power over itself, yet nothing ensures that it will be used wisely.’ We can no longer think of war as a solution, because its risks will probably always be greater than its supposed benefits. In view of this, it is very difficult nowadays to invoke the rational criteria elaborated in earlier centuries to speak of the possibility of a ‘just war.’ Never again war!” (emphasis mine)

In June 2023 when addressing the UN Security Council, Pope Francis would make this even more explicit.

“The time has come to say an emphatic ‘no’ to war, to state that wars are not just, but only peace is just: a stable and lasting peace, built not on the precarious balance of deterrence, but on the fraternity that unites us.”

In Magnifica Humanitas, Pope Leo has said not only “no to war.” He has also said “no” to any notion that war today can ever be just..

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Johnny Zokovitch is the former executive director of Pax Christi USA. He currently serves on the board of the Pax Christi International Fund for Peace and is in pastoral leadership at St. Cronan Catholic Church in St. Louis. Read more from Johnny at https://johnnyzokovitch.substack.com/ and sign up there to receive his articles directly to your email inbox.