If I intentionally kill another person I will be subject to a long term of imprisonment or even, in some jurisdictions, the death penalty. But if I kill 1,000 people, I might receive a medal; or if a million, I might be promoted to field marshal or even president, provided only that those killed come from another side of a border in a state known as “war”.
There is, however, a tradition which, while not resolving the paradox, does something to mitigate its evil consequences. This is known as the Just War….In Morality and War, David Fisher seeks to develop it [the theory] further in response to today’s circumstances. He is almost uniquely qualified for this task, having been trained as a moral philosopher and then having spent his career as a senior official in the UK Ministry of Defence.
The Just War doctrine has always insisted that “the onus of proof should rest on those seeking to disturb the tranquillity of the world by resorting to war”. It is permissible if and only if it is authorised by a competent authority, if it is for a just cause, if it is undertaken as a last resort and if the good likely to be achieved exceeds the harm of the war itself. And, of course, non-combatants should not be targeted.