This week, at a conference in Vienna, Austria on the humanitarian impact of nuclear weapons, Pope Francis issued a statement declaring that "nuclear deterrence cannot be the basis for peaceful coexistence between states."
A Vatican official told Sojourners in Vienna that the Holy See is seriously discussing whether the possession of nuclear weapons can be morally justified in our current multipolar world. The official quoted Pope John XXIII, who said "Nuclear weapons should be banned," and said that the time has come to embrace nuclear abolition.
The Vatican statement, titled "Nuclear Disarmament: Time for Abolition," argued that "the structure of nuclear deterrence is less stable and more worrisome than at the height of the Cold War," and said that "the very possession of nuclear weapons, even for purposes of deterrence, is morally problematic."
Since the beginning of the Cold War in the aftermath of World War II, the fundamental moral rationale for the possession of nuclear weapons has been the concept of deterrence. Simply put, the threat of massive annihilation rendered these weapons unusable — the very threat of such unacceptable destruction would, in theory, deter their use.