Because it is a real risk if things escalate. Quite terrifyingly simple
''In addition, ethical deterrence is an oxymoron. Theologians know that a nuclear war could never meet so-called ‘just war’ criteria. In 1966, the Second Vatican Council concluded: ‘Any act of war aimed indiscriminately at the destruction of entire cities or of extensive areas along with their populations is a crime against God and man itself. It merits unequivocal and unhesitating condemnation.’ And in a pastoral letter in 1983, the US Catholic bishops added: ‘This condemnation, in our judgment, applies even to the retaliatory use of weapons striking enemy cities after our own have already been struck.’ They continued that, if something is immoral to do, then it is also immoral to threaten. In a message to the 2014 Vienna Conference on the Humanitarian Impact of Nuclear Weapons, Pope Francis declared that: ‘Nuclear deterrence and the threat of mutually assured destruction cannot be the basis of an ethics of fraternity and peaceful coexistence among peoples and states.’
The United Methodist Council of Bishops go further than their Catholic counterparts, concluding in 1986 that: ‘Deterrence must no longer receive the churches’ blessing, even as a temporary warrant for the maintenance of nuclear weapons.’ In The Just War (1968), the Protestant ethicist Paul Ramsey asked his readers to imagine that traffic accidents in a particular city had suddenly been reduced to zero, after which it was found that everyone had been required to strap a newborn infant to the bumper of every car.
Perhaps the most frightening thing about nuclear deterrence is its many paths to failure. Contrary to what is widely assumed, the least likely is a ‘bolt out of the blue’ (BOOB) attack. Meanwhile, there are substantial risks associated with escalated conventional war, accidental or unauthorised use, irrational use (although it can be argued that any use of nuclear weapons would be irrational) or false alarms, which have happened with frightening regularity, and could lead to ‘retaliation’ against an attack that hadn’t happened. There have also been numerous ‘broken arrow’ accidents – accidental launching, firing, theft or loss of a nuclear weapon – as well as circumstances in which such events as a flock of geese, a ruptured gas pipeline or faulty computer codes have been interpreted as a hostile missile launch.
The above describes only some of the inadequacies and outright dangers posed by deterrence, the doctrinal fulcrum that manipulates nuclear hardware, software, deployments, accumulation and escalation. Undoing the ideology – verging on theology – of deterrence won’t be easy, but neither is living under the threat of worldwide annihilation. As the poet T S Eliot once wrote, unless you are in over your head, how do you know how tall you are? And when it comes to nuclear deterrence, we’re all in over our heads.
This essay was originally published in Aeon