The Vatican has long supported nuclear arms reduction and is seeking to build on the disarmament momentum generated by the United Nations treaty banning nuclear weapons. The Holy See’s efforts, like those of other pro-ban states, might seem quixotic given the countervailing policies of the nuclear weapons states. But as Rose Gottemoeller, NATO’s deputy secretary general, has said, “I think there is a huge moral impact of the Vatican on issues that relate to nuclear weapons deterrence and the disarmament agenda overall.” The Catholic Church and other religious bodies help ensure that morality is not an uninvited guest at an exclusive party dominated by nuclear realists. If nuclear policies lack moral (and legal) legitimacy, they will suffer from a lack of support at home and abroad. At the same time, the nuclear ban will contribute to a sustained movement for disarmament only if it is animated by a moral vision that is not confined by the straight-jacket of the nuclear status quo.
What is the moral vision of the Holy See and has it changed in recent years? Perhaps the most well-known articulation of the Catholic Church’s position on nuclear weapons can be found in the U.S. bishops’ 1983 pastoral, The Challenge of Peace. The bishops rejected both nuclear pacifism and nuclear realism. They elaborated an “interim ethic” whereby nuclear deterrence could be morally acceptable but only if limited to deterring the use of nuclear weapons, does not seek nuclear superiority, and is used as a step toward progressive disarmament. Numerous Vatican statements since the end of the Cold War appear to have abandoned this strictly-conditioned moral acceptance of nuclear deterrence in favor of nuclear pacifism. In 2015 a Vatican spokesperson told the UN Disarmament Committee that “nuclear deterrence and the threat of mutually assured destruction are irreconcilable with, and contrary to, an ethics of fraternity and peaceful coexistence among peoples and among States.” A Vatican Study Document concluded that “[I]t must be admitted that the very possession of nuclear weapons, even for purposes of deterrence, is morally problematic…. the condition that [deterrence] be ‘a step on the way toward progressive disarmament’…. has not been fulfilled—far from it.”
How should we interpret these and other statements? Clearly, the Church has concluded that the nuclear status quo is morally unacceptable for several reasons. Deterrence is not as necessary or stable as it might have been during the Cold War; deterrence is irrelevant to dealing with the most pressing security threats, such as terrorism; nuclear arsenals represent an unjust use of resources given unmet human needs; and, despite deep cuts since the Cold War, nuclear deterrence is not being used as a step toward disarmament but has become an end in itself. In short, the Church has made a series of prudential moral judgments that existing nuclear deterrents are morally unacceptable and much greater priority must be given to nuclear disarmament as the basis for lasting security. Disarmament has become the primary condition for the moral acceptability of deterrence. Given deep frustration with the lack of commitment on the part of the nuclear states to move toward this goal, the Holy See has joined others in a strategy of delegitimizing the nuclear status quo and finding new international mechanisms, such as the “humanitarian initiative” and the nuclear ban treaty, for making progress.
This strategy is being pursued in the context of a much wider agenda for peace. Nuclear abolition is integrated with a broader project of creating the conditions for a more just and peaceful world. The Vatican perspective is premised on the notion of “integral nuclear disarmament,” which ties the ban strategy to efforts to develop a global ethic of solidarity, or cooperative security. This approach is very different from approaches in which the nuclear question is defined largely in terms of narrow conceptions of national security.
The case for disarmament as a moral imperative is strong, but more work is needed to address the new moral challenges that will arise as the world moves toward global zero. An ethics of disarmament is needed to provide a firm moral foundation that can sustain the campaign for nuclear disarmament that has been reinvigorated by the nuclear ban treaty.
 Elizabeth Dias, “Pope Francis’ Latest Mission: Stopping Nuclear Weapons,” Time, April 10, 2015; accessed November 1, 2017, at http://time.com/3817021/pope-francis-nuclear-disarmament/?xid=emailshare.
 Archbishop Bernardito Auza, Statement to the First (Disarmament) Committee of the 70th Session of the General Assembly, New York, October 22, 2015.
 Study Document, “Nuclear Weapons: Time for Abolition,” Permanent Mission of the Holy See to the United Nations and Other International Organizations in Geneva, December 8, 2014.
Gerard Powers is the Director of Catholic Peacebuilding Studies at the Kroc Institute for International Peace Studies and the Coordinator of the Catholic Peacebuilding Network.