Since the atomic bombings of Hiroshima and Nagasaki, Church leaders have repeatedly emphasized the horror of nuclear war and the necessity of disarmament. In Pacem in terris, Pope John XXIII, who helped de-escalate tensions during the Cuban Missile Crisis, questioned the premise of deterrence: “The true and solid peace of nations consists not in equality of arms, but in mutual trust alone.” Nonetheless, the document suggested that the possession of nuclear weapons as a deterrent was permissible as long as progress was being made toward disarmament. Pope John Paul II made this position explicit in a 1982 address to the United Nations: “Not as an end in itself but as a step on the way toward a progressive disarmament, [deterrence] may still be judged morally acceptable.”
But, as Archbishop Wester documents in his letter, the Church and Pope Francis have in recent years begun to turn away from this “interim ethic.” In 2014, as part of the Vienna Conference on the Humanitarian Impact of Nuclear Weapons, the Holy See published “Nuclear Disarmament: Time for Abolition,” which found that the “very possession of nuclear weapons, even for purposes of deterrence, is morally problematic.” Francis echoed that verdict in a 2017 address: “Weapons of mass destruction, particularly nuclear weapons, create nothing but a false sense of security. They cannot constitute the basis for peaceful coexistence between members of the human family, which must rather be inspired by an ethics of solidarity.” In 2019, at the Peace Memorial in Hiroshima, he stated bluntly that the “use of atomic energy for purposes of war is immoral, just as the possessing of nuclear weapons is immoral.”
Archbishop Wester situates Francis’s comments on nuclear weapons within the Vatican’s more general shift toward nonviolence and stronger antiwar sentiment. Although just-war theory hasn’t been explicitly rejected by the Vatican, Francis and others have argued that it has often been misused as a mere list of conditions to check off before going to war. As Cardinal McElroy put it at the inauguration of the Catholic Institute for Nonviolence, “It was not meant to be a justification of war but a restraint on war, and it has lost a lot of that capacity.”