From Nuclear Deterrence to Disarmament: Evolving Catholic Perspectives

May 2015

By Gerard Powers

Pope Francis waves to pilgrims gathered in St. Peter’s Square at the Vatican on April 15. (Vincenzo Pinto/AFP/Getty Images)The Roman Catholic Church and other religious actors are confronting the nuclear issue with renewed vigor, condemning the nuclear status quo and pressing for more-dramatic steps toward disarmament.

Three developments have created this opportunity. First, nuclear disarmament, long the lonely call of religious leaders and anti-nuclear activists, has gone mainstream. Nuclear disarmament is now endorsed as a long-term policy goal by the Russian and U.S. governments and a global chorus of prominent military and political figures, led by the initiatives of George Shultz, William Perry, Henry Kissinger, and Sam Nunn[1] and the Global Zero campaign. Second, the series of international conferences on the humanitarian impact of nuclear weapons use has brought new attention to the legal and moral dimensions of nuclear weapons. Third, Pope Francis has made nuclear disarmament a priority, while the church in the United States, which played a leading role in the 1980s in addressing the morality of nuclear weapons, is deepening its involvement in the issue. This third development—the church’s deepening engagement on nuclear disarmament—is the focus of this article.

If this is a new moment for religious and moral voices in the nuclear debate, three issues need to be addressed. First, what is the church doing, and how does it understand its role? Second, to what extent has the church revised its position? Finally, what can religion and morality contribute to the nuclear debate in the coming years? 

The Church’s Role 

The Holy See routinely addresses the nuclear issue in statements such as those at the meetings of the International Atomic Energy Agency (IAEA) and the Conference on Disarmament. The Vatican has played an active role in supporting the international humanitarian-impact conferences. During the Vienna meeting, Francis issued his first major statement on nuclear weapons, which was accompanied by a statement by the Holy See’s representative to UN agencies in Geneva, and a lengthy “study document,” the Vatican’s most detailed treatment of nuclear weapons in many years. Although the study document was approved at the highest levels, it is akin to a white paper and not as authoritative as the Vatican’s formal statements on nuclear weapons. 

The U.S. Catholic bishops’ 1983 peace pastoral, “The Challenge of Peace,” remains the most comprehensive and well-known church document on nuclear weapons.[2] In recent years, the most comprehensive statements by U.S. bishops were a series of major talks by Baltimore Archbishop Edwin O’Brien at U.S. Strategic Air Command in Nebraska in 2009, the Paris Global Zero conference in 2010, and other venues. The bishops also have addressed specific issues, opposing major new funding for Bush and Obama administration programs to upgrade the U.S. nuclear arsenal and supporting ratification of the New Strategic Arms Reduction Treaty and the Obama administration’s negotiations with Iran on Tehran’s nuclear program. 

Furthermore, the U.S. bishops have been involved in a form of “Track 2” diplomacy with Iranian religious leaders.[3] With the support of the Nuclear Threat Initiative, the bishops have teamed up with the University of Notre Dame’s Kroc Institute; Georgetown University’s Berkley Center for Religion, Peace, and World Affairs; and Boston College to launch the multiyear Initiative on Revitalizing Catholic Engagement on Nuclear Disarmament. 

In considering these church interventions on nuclear weapons, it is important to keep in mind the church’s understanding of its role. Two important theological distinctions underlie official church statements on nuclear weapons. 

First, Catholic social teaching does not provide a blueprint for policy. Church leaders have insisted that morality matters in the nuclear debate and have offered a moral framework for evaluating nuclear use, deterrence, and disarmament. At their best, however, the leaders have avoided moralizing, or oversimplifying, this complicated issue. Church leaders have used their influence to press for policy initiatives they judge to be in keeping with their moral framework. Yet, in their analysis of nuclear weapons, they have taken considerable care in distinguishing moral principles, such as the prohibition against targeting civilians, from their prudential judgments about specific policy issues, such as support for U.S. ratification of the Comprehensive Test Ban Treaty (CTBT) and opposition to the first-use doctrine and deployment of the Strategic Defense Initiative. These prudential judgments are considered less authoritative than statements of principles because they involve applying these principles to complex political and strategic questions. 

Second, although religious leaders have a legitimate role to play in addressing public policy issues with significant moral dimensions, informed lay people, not church leaders, ultimately are responsible for making prudential judgments about how moral norms apply to specific policies. The bishops’ reluctance to offer definitive moral judgments on particular nuclear policies is not a function of excessive caution but of their understanding of the limits of morality and religious leadership. 

The Ethical Nexus 

The study document the Holy See released at the Vienna conference summed up the Vatican’s position on the interrelated ethics of nuclear use, deterrence, and disarmament. 

[I]t must be admitted that the very possession of nuclear weapons, even for purposes of deterrence, is morally problematic. While a consensus continues to grow that any possible use of such weapons is radically inconsistent with the demands of human dignity, in the past the Church has nonetheless expressed a provisional acceptance of their possession for reasons of deterrence, under the condition that this be “a step on the way toward progressive disarmament.” This condition has not been fulfilled—far from it. In the absence of further progress toward complete disarmament, and without concrete steps toward a more secure and a more genuine peace, the nuclear weapon establishment has lost much of its legitimacy.[4]

Is this a new position for the church? To answer that question, it is necessary to consider the ethics of use, deterrence, disarmament, and peace as distinct but intimately related issues.

The ethics of nuclear use is the starting point. In their 1983 peace pastoral, the U.S. bishops categorically rejected, as indiscriminate and disproportionate, the use of nuclear weapons against cities or multiple military targets within cities. They opposed first use of nuclear weapons and were deeply skeptical about the morality of even a limited retaliatory, or second, use in response to a nuclear attack. Those judgments were based on the bishops’ concerns about the consequences of breaking the nuclear taboo and the inherent risks of escalation. Nevertheless, they did not rule out any conceivable second use, acknowledging the moral possibility that an isolated use—for example, against a missile silo in Siberia—might be discriminate and proportionate. In 1993 the U.S. bishops went further and said they “abhor any use of nuclear weapons.”[5] This should be considered a hortatory statement, not a change in their moral analysis of use. 

Archbishop Bernardito Auza, permanent observer of the Holy See to the United Nations, participates in the conference “Nuclear Weapons and the Moral Compass” at the UN on April 9. (Global Security Institute)Recent Vatican statements, however, have been unequivocal about the immorality of use. The 2014 study document flatly stated that “[u]se of nuclear weapons is absolutely prohibited.” In an address to the IAEA last September, the Vatican’s deputy foreign minister, Monsignor Antoine Camilleri, supported the view that “the mere existence of these weapons is absurd and that arguments in support of their use are an affront against the dignity of all human life.”[6] This position is based on two sets of concerns. One arises from the likelihood that any use of nuclear weapons would cause unnecessary, irreversible suffering and would be indiscriminate and disproportionate, especially given the risk of escalation. The other is the consequences of breaking the nuclear taboo, including undermining prospects for disarmament.[7]

This unequivocal rejection of any use raises questions about the moral status of deterrence. In Catholic moral theology, it is immoral to threaten that which it is immoral to do. Hence, the moral paradox of theories of nuclear deterrence that hold that the way to prevent the unthinkable is to threaten it. The bishops rejected two approaches to the morality of nuclear deterrence: that of nuclear pacifists, who argued that because nuclear weapons are inherently indiscriminate and disproportionate, the threat of use in nuclear deterrence is immoral, and that of the defenders of deterrence, who argued that it could be justified as a necessary evil. Instead, following the lead of the Vatican, the bishops elaborated an “interim ethic” whereby nuclear deterrence could be morally acceptable if it met three criteria: sole use, meaning that its use is limited to deterring the use of nuclear weapons; sufficiency, meaning that it is not based on achieving nuclear superiority; and disarmament, meaning that it is used as a step toward disarmament.

Numerous Vatican statements since the end of the Cold War have brought into question even this strictly conditioned moral acceptance of deterrence. For example, in a talk at Georgetown in 2010, Archbishop Celestino Migliore, the Holy See’s permanent observer to the United Nations, decried the “second nuclear age” (the first being the Cold War), when nuclear terrorism is a threat, nuclear weapons are proliferating, and these weapons “are no longer just for deterrence but have become entrenched in the military doctrines of the major powers.” Migliore concluded that “[i]t is evident that nuclear deterrence is preventing genuine nuclear disarmament. Consequently, the conditions that prevailed during the cold war, which gave a basis for the church’s limited toleration of nuclear deterrence, no longer apply.”[8] 

Vatican statements cite several reasons why “the system of nuclear deterrence can no longer be deemed a policy that stands firmly on moral ground.”[9] First, a system that is based on a conditional intent to use nuclear weapons in ways that will lead to mass destruction is morally problematic. Second, “the structure of nuclear deterrence is less stable and more worrisome than at the height of the Cold War” due to the larger number of states possessing nuclear weapons and the increased risk of nuclear weapons use, including by terrorists and unstable nuclear-armed states.[10] Moreover, nuclear weapons do not deter terrorism, intrastate conflicts, and other major threats today. Third, although major cuts in the numbers of nuclear weapons have taken place, nuclear deterrence has not been used as a step toward disarmament but has become an end in itself, a principal impediment to disarmament. Fourth, the “peace dividend” that was supposed to come with the end of the Cold War has not materialized as “enormous amounts of money are still being spent on ‘modernizing’ the nuclear arsenals of the very states that are ostensibly reducing their nuclear weapons numbers.”[11] 

One way to read these documents is that the Vatican has become a nuclear pacifist. The study document concludes, “Now is the time to affirm not only the immorality of the use of nuclear weapons, but the immorality of their possession, thereby clearing the road to nuclear abolition.”[12] The U.S. bishops’ insistence that it is time to “move beyond deterrence” would seem to reinforce this point.

Another, more nuanced interpretation should be considered—that the Vatican has not abandoned its strictly conditioned moral acceptance of deterrence but has revised the way it applies that moral framework. It has moved from enunciating a moral framework for deterrence to making increasingly specific and clear judgments about whether the sole-use, sufficiency, and disarmament conditions of that framework are being met in practice. Based on its reading of the geopolitical signs of the times, it has concluded that nuclear deterrence is not as necessary or stable as it was during the Cold War, that the nuclear powers are making insufficient progress in meeting the conditions, and that they do not seem to have the will to do so. This is not a moral rejection of the concept of deterrence itself, but a prudential judgment—based on an assessment of a host of political, security, and strategic issues—about the morality of the particular structure of deterrence as it exists today. 

Even if one does not accept the Vatican’s assessment of these issues, supporters of the status quo in U.S. or Russian nuclear policy, in 2015 as in 1983, will find little to comfort them in the bishops’ strictly conditioned acceptance of deterrence. Yet, condemning existing nuclear deterrents is not tantamount to condemning the idea of nuclear deterrence. Deterring the use of nuclear weapons remains essential, but existing systems of deterrence need to be dramatically revised in order to meet the three conditions, with much greater priority given to nuclear disarmament as the basis for lasting security.

This dramatic shift in emphasis from the first two conditions (sole use and sufficiency) to progress toward nuclear disarmament is another way the church has revised its application of the conditions. Disarmament has become the primary condition for the moral acceptability of deterrence, the lens through which the other two conditions are viewed. The main purpose of the sole-purpose and sufficiency criteria is no longer to ensure crisis stability and arms race stability, although those remain important. Rather, these conditions now serve mainly to support the disarmament criterion. They do that, for example, by delegitimizing proposals to modernize nuclear arsenals and by providing a rationale for reducing Russian and U.S. stockpiles to the small number of weapons required for a minimal deterrent. 

The church is not calling for immediate, unilateral nuclear disarmament. Rather, it is insisting that it is long past time to move beyond a preoccupation with and moral complacency about nuclear deterrence. Instead, the moral priority must be doing the difficult moral and policy work necessary to move much more rapidly toward nuclear disarmament—to achieve a non-nuclear ethic. 

Yet another way in which the church is revising its use of the strictly conditioned moral acceptance framework relates to strategy. If one wants to make progress on nuclear disarmament, it is necessary to delegitimize the nuclear status quo and find new international mechanisms for moving forward. Archbishop Silvano Tomasi’s statement during the Vienna conference refers to this new strategic calculus. “We are now witnessing a renewed awareness after two decades lost to the cause of nuclear disarmament…. The ‘humanitarian initiative’ is a new hope to make decisive steps towards a world without nuclear weapons.” Tomasi added that the partnership among countries, civil society, international organizations, and others “is an additional guarantee of inclusion, cooperation and solidarity. This is not an action of circumstance. This is a fundamental shift that meets a strong quest of a large number of the world’s populations which would be the first victims of a nuclear incident.”[13]

The church’s shift from the ethics of nuclear use and deterrence to the ethics of disarmament must be understood in the context of its broader ethic of peace. The bishops’ interim ethic of strictly conditioned moral acceptance of deterrence is less a function of time than context. Although some advocates of global zero would disagree, the church considers nuclear abolition to be a long-term objective that ultimately is as much about creating the conditions for a more just and peaceful world order as it is about the narrower issue of nuclear arms control and disarmament. 

Nuclear abolition does not require an end to war, but in the church’s view, it does require more than rethinking nuclear policies. It requires the development of a global ethic of solidarity, or cooperative security. National security doctrines that overemphasize military security should be replaced by the concept of “human security,” which focuses on “socio-economic development, political participation, respect for fundamental human rights, strengthening the rule of law, [and] cooperation and solidarity at the regional and international level.”[14] 

Nuclear weapons are an impediment to achieving this ethic of cooperative security. Not only are nuclear doctrines premised on the double standard in the nuclear Nonproliferation Treaty (NPT), whereby a few countries are allowed to possess nuclear weapons while most are required to abstain, but they are closely associated with doctrines of national security rooted in military, political, and economic dominance. They are associated with rigid conceptions of sovereignty, especially with the sacrosanct area of national security, that leave little room for strengthening international law and institutions. Nuclear weapons also raise issues of distributive justice. According to Francis, “Spending on nuclear weapons squanders the wealth of nations. To prioritize such spending is a mistake and a misallocation of resources which would be far better invested in areas of integral human development, education, health and the fight against extreme poverty.”[15]

A cooperative security framework in which nuclear weapons are banned will require a fundamental reconsideration of the relationship between sovereignty and security and a redefinition of the responsibilities and rights that come with sovereignty. The nuclear have-nots will have to continue to pursue an ethic and practice of restraint in forgoing nuclear weapons. Because of the risks they have imposed on the world by possessing nuclear weapons, the nuclear haves bear a much heavier burden. They must ultimately renounce their reliance on nuclear weapons as a basis for their national security; they must forgo military, political, and economic dominance as central tenets of their foreign policies; and they must take the lead in building a system of cooperative security that will make a global ban more likely and more sustainable. 

Do Religious Voices Matter? 

Religious leaders have been preaching nuclear disarmament for decades. They have had an impact, but it is mostly indirect. Their most important contribution has been to help ensure that morality is not an uninvited guest at an exclusive party dominated by realists. Although the moral dimension of nuclear issues is not always prominent, it should not be underestimated. 

The NPT is inherently unstable and morally flawed because it is based on a double standard. Nuclear deterrence depends in part on the moral credibility of the threats involved. U.S. nuclear policies cannot survive in the long term if major religious bodies and the general public lose faith in their ultimate moral legitimacy. Rose Gottemoeller, U.S. undersecretary of state for arms control and international security, underscored this point in explaining her concerted effort to engage the Holy See on nuclear disarmament issues in recent months: “I think there is a huge moral impact of the Vatican on issues that relate to nuclear weapons deterrence and the disarmament agenda overall.”[16] 

Nuclear disarmament has gone mainstream for a variety of reasons, but the moral imperative is helping to drive this movement. This long-term movement can be sustained only if it is animated by a moral vision of possibilities that can scarcely be imagined, a moral vision whose credibility will depend on the quality of its ethical analysis of nuclear use, nuclear deterrence, nuclear disarmament, and a just peace. 

Another important role that religious bodies can play is to help democratize an otherwise elite debate. The genius of the nuclear freeze movement in the 1980s was that it helped get nuclear policy out of Washington offices and into town halls and church basements. Catholic bishops and other religious leaders did not lead this campaign, but they provided moral credibility and institutional authority to legitimize the concerns of an already aroused public. Their vast institutional infrastructure of parishes, dioceses, schools, universities, religious orders, lay organizations, and media gives them the ability to mobilize and motivate grassroots activists on nuclear issues. That has been increasingly difficult in the past 25 years as the nuclear issue has moved to the margins of U.S. foreign policy and consequently has receded in the public consciousness. It remains possible, however, to mobilize Catholics on issues such as ratification of the CTBT, where the church’s broad moral and policy concerns find a concrete legislative handle. 

Unfortunately, the policy debate on nuclear disarmament is now ahead of the moral debate. This article has outlined the contours of the church’s moral case for disarmament, which it is pressing with ever more urgency. 

That moral case will be strengthened as the church addresses an ethics gap on nuclear disarmament that is comparable to the ethics gap on nuclear deterrence of the 1940s and 1950s.[17] The arguments for the moral imperative of disarmament are clear enough. The element that is largely missing is serious ethical reflection on the new moral challenges that will arise as the world moves toward that goal. The world needs an ethic of nuclear disarmament that is as sophisticated as the ethic of nuclear use and deterrence produced during the height of the Cold War. 

A major issue that must be addressed is the relationship between deterrence and disarmament. If progress on disarmament is now the church’s principal condition for the moral acceptability of deterrence and the church has embraced a no-use ethic, what of the moral paradox of deterrence? If the nuclear powers move to the minimal deterrent that is considered the next step in the nuclear disarmament process, will there be an increased tendency to move from targeting of the enemy’s nuclear forces to the city-busting targeting that the church has unequivocally condemned? If achieving global zero would make nuclear weapons even more valuable, more usable, and more destabilizing given the risk of nuclear breakout, what forms of deterrence would be morally acceptable then? 

In both cases, the church’s position would seem to require further exploration of the ethical dimensions of the concept of existential deterrence—that is, that nuclear use can be deterred by the mere fact that a country possesses or can quickly rebuild its nuclear arsenal.[18] The church also might have to reconsider its position on missile defense. The church has opposed deployment of missile defenses in part because they are considered destabilizing. In a world near or at global zero, would shared missile defenses be less morally problematic as a supplement to other forms of deterrence? 

This can be a new moment for religious voices on nuclear issues. That will require even more concerted efforts by religious leaders and a wealth of new initiatives of the kind undertaken by the U.S. bishops and some Catholic universities. The challenge will be to close the ethics gap on these and other issues and to develop a new generation of religious leaders, scholars, and practitioners with the competence and long-term commitment needed to help maintain momentum toward global zero. 

Gerard Powers is director of Catholic Peacebuilding Studies at the Kroc Institute for International Peace Studies at the University of Notre Dame. From 1987 to 2004, he was an adviser on nuclear issues for the U.S. Conference of Catholic Bishops. He coordinates the Initiative on Revitalizing Catholic Engagement on Nuclear Disarmament, a joint effort of the Kroc Institute; Georgetown University’s Berkley Center for Religion, Peace, and World Affairs; Boston College; and the U.S. bishops’ Office of International Justice and Peace, with support from the Nuclear Threat Initiative. 


1. For the first effort of the four men on this issue, see George P. Shultz, William J. Perry, Henry A. Kissinger, and Sam Nunn “A World Free of Nuclear Weapons,” The Wall Street Journal, January 4, 2007. 

2. National Conference of Catholic Bishops, “The Challenge of Peace: God’s Promise and Our Response,” May 3, 1983.

3. See Arms Control Association, “US-Iranian Religious Leaders’ Dialogue: The Relevance of Moral Questions Related to Nuclear Weapons,” October 29, 2014, (transcript of event at Carnegie Endowment for International Peace). Track 2 diplomacy is informal, unofficial diplomacy by nonstate actors, usually intended to complement formal, official “Track 1” diplomacy by states. 

4. Permanent Mission of the Holy See to the United Nations and Other International Organizations in Geneva, “Nuclear Weapons: Time for Abolition,” December 8, 2014, (hereinafter study document). 

5. United States Conference of Catholic Bishops, “The Harvest of Justice Is Sown in Peace,” November 17, 1993, p. 33.

6. Antoine Camilleri, Address to the 58th General Conference of the International Atomic Energy Agency, Vienna, September 22, 2014.

7. Dominique Mamberti, Address to the 56th General Conference of the International Atomic Energy Agency, Vienna, September 19, 2012.

8. Celestino Migliore, Woodstock Theological Institute, Georgetown University, March 16, 2010. For a summary of the talk, see Thomas Reese, “Vatican Questions Nuclear Deterrence,” Georgetown University, May 12, 2010,

9. Study document, p. 4. 

10. Ibid., p. 3. 

11. Dominique Mamberti, Statement at the High-Level Meeting on Nuclear Disarmament, 68th Session of the UN General Assembly, September 26, 2013,

12. Study document, p. 6.

13. Silvano M. Tomasi, Statement at the Vienna Conference on the Humanitarian Impact of Nuclear Weapons, Vienna, December 9, 2014,

14. Ibid.

15. “Message of His Holiness Pope Francis on the Occasion of the Vienna Conference on the Humanitarian Impact of Nuclear Weapons,” December 7, 2014.

16. Elizabeth Dias, “Pope Francis’ Latest Mission: Stopping Nuclear Weapons,” Time, April 10, 2015,

17. For a more detailed explanation of this gap, see Gerard Powers, “The Nuclear Ethics Gap,” America, May 17, 2010, p. 11.

18. See, for example, J. Bryan Hehir, “There’s No Deterring the Catholic Bishops,” Ethics and International Affairs, Vol. 3, No. 1 (March 1989): 277.