Dr. Kevin Miller, a moral theologian at Franciscan University of Steubenville, explained that the concept was a well established part of Church teaching and thought.
“The Catechism of the Catholic Church does a nice job of summarizing the criteria for entering into the use of military force for self-defense,” Miller told CNA, “though I tend to think of just war as more of a ‘doctrine’ than a ‘theory’ in the Church.”
Miller said the Church’s moral criteria are divided into two categories – the ius ad bellum and the ius in bello, covering the criteria for resorting to war and how it is to be conducted once begun.
“Regarding proportionality, the Catechism says that ‘the use of arms must not produce evils or disorders graver than the evil to be eliminated.’ That would be the criterion that [President] Trump seems to be alluding to in saying what he did.”
While the prospect of air strikes causing casualties in response to shooting down an unmanned drone presents a clear case for weighing the proportionality of any response, Miller said, there can be some broader confusion about what proportionality means.
“It does not necessarily mean you cannot take the lives of more enemy combatants than have been lost on your side, that would be almost to say there was an obligation to lose the war. Nor does it necessarily mean that you cannot prosecute a war of self-defense in response to an initial strike – take for example the attack on Pearl Harbor, which was not necessarily intended to precede an invasion of the United States but nevertheless triggered a just response of war with Japan.”
Considering the specific example offered by Trump’s comments, Miller said that, at least based on what has been reported, the reasoning was less straightforward.
“If you think about the act of shooting down a drone – is that intended to be the beginning of a military action leading to further deadly damage to either American or allied personnel or interests? It might be clear that such an act was intended as a provocation, but not necessarily to war.”
Dr. Taylor Patrick O’Neill, assistant professor of theology at Mount Mercy University, told CNA that the ongoing nature of a threat was an important part of invoking a just military response.
“The first criterion for the use of military force is, of course, a just cause,” O’Neill told CNA.
“I think that in response to an act which has not yet caused any casualties, which is not part of an ongoing pattern of military aggression with lives at stake, there is a real question here about the just cause and the proportionality of engaging in a response which would certainly take lives – maybe many lives and even civilian ones at that.”
Miller agreed that responding with deadly force to a non-deadly provocation requires serious scrutiny.
(Story cotinues below)
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“If it really is the case that the response to, say, the shooting down of an unmanned drone, is only intended to take out the infrastructure which made that possible and to prevent it happening again, it is all the more clear that proportionality really does come to bear when you are looking at taking human life – especially if those lives might include civilians. It becomes very problematic,” Miller said.
Modern conflicts often involve remote means of warfare and targets which are of unclear military status, such as governmental intelligence posts, radar stations, or other logistical installations. While the personnel in them might be primarily military, the presence of civilians has to weighed carefully in discerning military action.
“The classification of people involved can be very difficult to discern in modern conflicts,” O’Neill said.
“We don’t necessarily see artillery shelling enemy lines. With strikes from distance on military targets, there are people involved who might not be military personnel: they might be government intelligence workers or people in a grey area, but then there’s the possibility of just the civilian janitor in the building, how do you put them in the balance of proportionality? It makes things very difficult.”
O’Neill said that with modern means of warfare, there is a very high burden on governments to take all measures possible to limit the loss of potentially innocent human life.
“To have the moral justification and to make some calculus of proportionality, you have to have some good intelligence about who could be harmed – obviously there can be unintended consequences but you have to have a good amount of information about what the effects of a military action could be before you can judge if it is a just response.”