Pope Francis said late in 2017 that the nuclear arms race
had become irrational and immoral. The irrationality itself rendered even just
the possession of nuclear weapons as immoral, according to the pope. Whereas
past popes had recognized deterrence as a legitimator, both irrationality and
the extent and “upgrading” of such weapons were factors in Pope Francis’s
admittedly personal view. Yet was his basis only moral, or religious in nature?
The full essay is at "The Pope on Nuclear Weapons."