Gerald W. Schlabach
Catholic Institute for Nonviolence
Rome, 10 September 2026
It was the tumultuous year of 1968, and a Mennonite peace activist named Ivan Kauffman was well placed within the “historic peace church” that had formed him to resist the United States’ war in Vietnam. After all, he was executive secretary of the “Peace Section” of Mennonite Central Committee, his church’s well-respected relief and development organization. Yet he made a momentous decision that risked alienating him from his family, community, and social networks. He became a Roman Catholic.
Viewed from the outside, his move could not have been more counterintuitive. Average U.S. Catholics were not even known for applying the just-war tradition, so much as for an unquestioning support for the war. The “completely fresh appraisal of war” that Vatican II had called for, less than 3 years earlier, had barely begun.
Yet Ivan had not given up his commitment to active nonviolence. No — however counterintuitively — it was his very commitment to peacemaking that led him into the Catholic Church. For this was his intuition: “Even Christians who are most committed to peacemaking will be limited in what they can do for peace in the world until churches share a common witness by making peace among themselves.”
Or to put forth my own thesis: To work for the unity of the Church is itself a peacebuilding strategy.
Or to riff on the famous dictum of Pope Paul VI: If you want peace, work for church unity.
Since the Protestant beginnings of the ecumenical movement over a century ago, one of its goals has been to be able to speak for peace with a unified voice. And Catholics should be able to recognize the potential. After all, the “ministry of unity” that is the papacy has allowed Pope Leo to emerge as the world’s leading voice opposing the US-Israeli war in Iran. Here then are two interconnected implications.
Implication no. 1: Especially in a global Church with “Catholic” in its name, we must unlearn the nationalistic habits that fracture church unity. So-called Christian nationalism in its contemporary manifestations is getting much scrutiny these days. Yet it is not really a new phenomenon. Rather, it is a desperate attempt to reinstate the worst of what some call “Constantinianism” and others call “Caesaropapism” – the close identification of Christianity with particular nation-states or empires.
Pope John XXIII made clear in his opening address to the Second Vatican Council that the patronage of princes has proven more of an impediment to the faithful mission of the Church than a blessing. In Pope Leo’s chrism mass on Holy Thursday this year, he too lamented ways in which that mission has sometimes, historically, been “distorted by a desire for domination” when instead it should be disrupting “the imperialist domination of the world” from within.
But if Christian nationalism is wrong, what is right? For nonviolence to indeed move to “the heart of the Catholic Church,” we need a peace ecclesiology — a theology of church as a peaceable, peacebuilding people — that welcomes, embraces, and consistently sustains nonviolent practices.
Near the end of his life, leading Jesuit theologian Karl Rahner wrote that the fundamental significance of the Vatican II was that the Roman Church was starting – though only starting – to come to terms with the fact that it has become a “world Church.” Indeed, he wrote, it finds itself living everywhere in diaspora — spread among many nations, typically in the minority, and rarely enjoying guarantees of political control. That the Church is a transcultural world Church, he wrote, has always been true potentially. But until Vatican II, Catholicism’s focus on Europe had long kept it from grappling with the implications of its necessarily global and multicultural identity.
There are biblical and patristic resources for this task. When the council affirmed that the Church is a people ever on pilgrimage through history, it tapped into these resources. As Pope Francis liked to say, “time is greater than space.” God’s purposes need time, therefore, more than then they need territorial control. When the author of 1st Peter wrote to the “sojourners” or “exiles” of the new Christian diaspora, he addressed them as a “holy nation.” When we hear the word “nation” today, most of use think first of nation-states like Italy, or Japan, or Malaysia, rather than peoples like the Maya, the Romani, the Hmong, or the Oromo of East Africa. While there are roughly 200 nation-states in the world, anthropologists estimate that there are some 5-to-8,000 nations, only a few of which will ever enjoy territorial control. In this sense, the 1st-century Christians of 1st Peter were also a nation, but not a “nation-state” at all.
Thus, when Cyprian and later Basil the Great were being interrogated and threatened with exile they both replied — a sea and a century apart — that exile was no threat at all. As Christians, they objected, they were at home in every land because they were strangers even in their own cities. Even Augustine, a century after the Constantinian settlement, retained this sensibility. In City of God, his definitive word on how the heavenly city still on pilgrimage should live amid the earthly city was to emulate the Hebrew exiles in Babylon. As Jeremiah had written, they should “seek the shalom / well-being” of the very city that held them captive without bowing down to its idolatrous claims. Like Daniel and his three Hebrew friends in the Babylonian civil service, embracing life in diaspora should mean service to the common good, but only if they — and we — are stubbornly clear about our primary allegiance to God.
To fully embrace our Catholic Christian identity as a people living in diaspora – a transnational “nation” that crosses the borders of every nation-state – this is, I argue, key to living out a peace ecclesiology. It is key, in other words, to forming Catholic disciples and communities who expect and know how to resist the idolatrous demands of militaristic governments while struggling for justice through the “force more powerful” of nonviolence. And all this has everything to do with church unity because every time a Christian prioritizes their identity within a particular tribe or nation-state over their allegiance to Jesus Christ, they fracture their identification with Christians in other lands, and with that, the unity of the Church.
Indeed, having followed debates over war, peace, militarism and foreign policy between Christians for decades, I have come to a conclusion: It is the rare Christian who decides either to support or resist wars because they have either worked through classic arguments for or against Christian pacifism, or worked through the nuances that might distinguish absolute pacifism from strategic nonviolence, or have carefully tested the latest call to arms against the grid of just-war criteria. The problem is that something else almost always overrides such deliberation: Yes, we know war is evil — many will even admit. Yes, we know Jesus taught and lived out nonviolent love. But we have a just cause. Isn’t that enough for a just war? After all, you gotta do what you gotta do. And whether people say so or not, they believe that they “gotta do what they gotta do” because they are German, or Russian, or Argentine, or Hutu, or U.S. American — first.
Implication no. 2 follows from this: We do more to reduce violence when we unite with stringent, conscientious practitioners of the just-war theory to oppose militarism and crusading mentalities, than when we imagine that we can entirely dislodge just-war theory. Here I am concurring with some of what Tobias Winright wrote in an article arguing for the ongoing relevance of just-war thinking. Winright closed by citing his and my pacifist professor at Notre Dame, John Howard Yoder: “As Mr. Yoder, a pacifist, counseled, nonviolence advocates and just war proponents should stop attacking each other and instead ‘spend more energy…[on] their responsibility to challenge the realists, crusaders, and Rambos on their “right” who in fact are shooting up the world.’”
And really, now: can the just-war tradition simply go away? G.K. Chesterton famously called tradition “the democracy of the dead” — or as we might tweak him for the church today, tradition is the synodality of the dead. Our ancestors in the Church continue to vote with their legacy. And it is a legacy that we in this room actually welcome, at least in part, more than we may want to admit. After all, even if we could excise just-war thinking from Catholic tradition, do we really want to deny — much less undo — its contribution to building up principles of international law and human rights conventions? No, we readily appeal to these in our advocacy.
Rather than try to excise the just-war tradition, we should work to put it in its place. I state our task that way deliberately. Just-war proponents may chafe at the implication that their tradition needs to be “put in its place.” Nonviolence proponents may need to accept that just-war principles do still have a place. But we may need some equal-opportunity discomfort to forge a deeper consensus on the way to church unity.
Though I moved from the Mennonite to the Catholic tradition 25 years ago, I do think we can learn from historic peace churches like the Mennonites about how to put the just-war tradition in its place. Knowing that they represent a minority position and that policymakers rarely share their ethical frameworks fully, Mennonite thinkers have argued that just-war principles can serve as a “second language” or a “situated discourse” when Christian pacifists and others deeply committed to active nonviolence enter the public square in opposition to specific wars. In fact, Pax Christi itself is doing this already. For example, it recently joined with other organizations in denouncing Israeli military actions that “violate the principle of proportionality and the prohibition of indiscriminate attacks” — citing two of the most critical just-war criteria now embedded in international law.
Might clarity about our first and second languages be one way to affirm a continuing utility of just-war principles even while encouraging the magisterium’s deepening affirmation of gospel nonviolence? The very title of our sessions this afternoon allows for this possibility. As we move nonviolence into the heart of the Church, we need ways to speak prophetically and constructively with others on our periphery, in ways they more readily understand. A just-war framework can be recognized as the church’s second language, to be used in “the Church’s continuing efforts to limit the use of force by the application of moral norms” – as Pope Francis allowed in his 2017 World Day of Peace message. But that in turn would imply the need for all that Pax Christi and CNI are advocating in order to make gospel nonviolence the first language of Catholic Christians.
So if you want peace, work for church unity. Live across borders. Be bilingual.