ch-year-old.

The classical Just War doctrine: Jus in bello

In this, the second article of a two-part series, Rev Ken Webb FSSP discusses what Aquinas and other philosophers have had to say about when and how a war may be waged justly.

Previously we considered the jus ad bellum component of the classical just war doctrine, which set forth the conditions by which war might be initiated in a manner that could be held to be “just”, that is to say, morally permissible. We turn now to the second component of the just war doctrine, which is concerned with the conduct of a belligerent in the waging of war. We have seen that the jus ad bellum demands that a state may only declare war in order to defend or to restore justice. Yet justice demands that there must be a clear distinction made between a guilty enemy against whom it is lawful to make war and the innocents who may not be harmed.

Francisco Vitoria, following in the tradition of St Thomas Aquinas, holds that “the deliberate slaughter of innocents is never lawful in itself” and that such slaughter is condemned by the natural law. Insofar as citizens of a belligerent country are involved in the unjust attack against another nation, they are held to have lost the status of innocents and are considered legitimate military targets. The distinction which must be made between the combatant and the non-combatant reflects the distinction between legitimate and illegitimate military objectives; and it is clearly delineated both in the classical just war doctrine and in modern developments which have evolved from it.

It naturally follows that determining who, precisely, constitutes the class of innocents is centrally important. Women, children and the elderly have traditionally been accorded the status of innocents, along with the rest of the peaceful civilian population. Those civilians who directly contribute to the war effort, however, such as munitions workers or those in the shipbuilding industry, become – in the application of the classical just war doctrine – legitimate military targets, because they are directly contributing to the war effort of a nation.

The distinction between combatant and non-combatant, it is important to note, applies only to the direct and intentional targeting for destruction. Just war theorists, from St Thomas Aquinas to Francisco Suarez SJ, all recognised that as a result of collateral and unintended damage, many innocent lives may be lost. At this point, the principle of double effect must be considered.

Double effect

The principle of double effect is a central element of the jus in bello portion of the classical just war doctrine. The principle, set down by St Thomas, holds that an act from which both good and evil consequences flow is permissible (a) if the evil result is an unintended side effect, (b) if the evil which results is proportional to the good which is achieved, and (c) if there is no other way of achieving the desired good. Let us consider St Thomas’ own words:

“Nothing hinders one act from having two effects, only one of which is intended, while the other is beside the intention. Now moral acts take their species according to what is intended, and not according to what is beside the intention, since this is accidental as explained above … And yet though proceeding from a good intention, an act may be rendered unlawful, if it be out of proportion to the end."

Suarez incorporated the principle of double effect into his discussion of the just conduct of war. He recognised the clear necessity to distinguish between combatants and non-combatants (innocents). At the same time he acknowledged the reality that innocents will invariably become casualties as the result of legitimate military operations. This would especially hold true in the case of sieges or battles for key population centres. Suarez applies, in such cases, his own version of the principle of double effect. He states that if a belligerent has satisfied the demands of the conditions laid down by the jus ad bellum, and thus is fighting for a just end, then the means which he employs to attain a legitimate end must themselves be considered just. In this case, the death of innocents is not sought as an aim of operations, but is rather an incidental consequence. “[H]ence, it is considered not as voluntarily inflicted but simply as allowed by one who is making use of his right in a time of necessity.”

Now Suarez is not here suggesting that evil may be done to achieve a good end. Both he and St Thomas would have rejected such a claim. Rather, the evil consequences (the death of many innocents as a result of legitimate military action) are not intended as an end in itself. If they are proportionate to the good which is achieved, and if there are no other means to achieve the end sought, then such consequences are permitted to follow incidentally. In Suarez’s view, legitimate ends render whatever means are used to achieve them legitimate as well. Thus, military action against legitimate military targets, action which will inevitably include a loss of innocent lives, can be justified by the principle of double effect, as Suarez articulates that principle.

Too permissive?

A strong argument can be made, however, that the position of Suarez on what means may legitimately be used in the conduct of war is too permissive, in fact so permissive that it renders his use of the principle of double effect redundant. For while he recognises the importance of the status of innocents in regard to military action, he seems in this case to issue a carte blanche to the initially just belligerent to employ any and all means available. This he seeks to justify by arguing that if the initial end is just, the means used to achieve the end are by definition just. Considered as a moral argument, the conclusion does not follow.

St Thomas recognised, along with most thinkers in the classical just war tradition, that if the means employed to wage war are intrinsically immoral or out of all proportion in the evil which they inflict, then the waging of war would become unjust. It seems that to abide by the just war doctrine’s basic principles, as well as to satisfy the conditions which it establishes, one cannot safely follow Suarez in his argument that just ends render just any means employed to achieve those ends.

A contemporary application of the double effect principle – this application being much more consistent than Suarez’s with the thought of St Thomas, and with the classical just war tradition as expressed by St Thomas’s followers – is provided by Michael Walzer. His argument, in a slightly modified form, is as follows: it is permitted to perform an act likely to have evil consequences (the death of innocents) provided that the following four conditions hold:

i. The act is in itself either morally good or indifferent, that is, it must be a legitimate act of war.
ii. The direct effect of the act is morally acceptable – the destruction of enemy military personnel or resources.
iii. The intention of the actor is good, he aims only at the acceptable effect, and the evil effect is neither one of his ends nor is it a necessary means to his ends.
iv. The good achieved must compensate for the evil consequences; that is to say that it must be justifiable according to the rule of proportionality.

The above concise exposition of the principle of double effect meets the criterion of consistency with the principles that St Thomas, and his followers, articulated. Let us consider an example to make clear how the double effect principle works in practical terms. The scenario is like that of hundreds of battles which took place to liberate western Europe during World War II, and bears striking resemblance to more contemporary military operations as well, such as some of the battles recently fought by the coalition led by the United States to secure Iraq in the wake of Saddam Hussein’s overthrow.

Unavoidable losses

It is helpful to recall that in the case of any siege or battle for a city, where innocents are likely to be killed indirectly, the demands of the jus ad bellum become even more important, given the likely consequences to non-combatants during the course of fighting to secure population centres. While some deny that any battle which sees civilians killed could ever be considered morally acceptable, the classical just war tradition – as expressed by thinkers such as Suarez and Vitoria, who specifically considered the question – argue that such a loss is in fact unavoidable, especially in battles for cities.

Take the case of a commander who is ordered to capture a city of key military importance. This city is heavily defended by an entrenched enemy throughout the town, but especially in several known sectors. It is also being defended by an undetermined number of civilians living around the area. The commander in this instance could legitimately intend to assault the town and the known enemy strongpoints, with all of the firepower and forces at his disposal, striking the enemy forces there, even though innocent casualties will inevitably result. How do we reach this conclusion?

This assault would be legitimate according to the conditions established to apply the principle of double effect. The act is a legitimate act of war, because it is directed at a legitimate military end (the capture of a militarily significant objective – a city) and the means by which it is achieved is though attacking and defeating the enemy soldiers who are defending the city.

The second condition is met because the intended direct effect of the act is the destruction of enemy soldiers. The intention of the actor is good because he is aiming only at the destruction of enemy soldiers, and the evil effect is not an end, nor is it a necessary means to his end. If, however, the attacker was to round up the families of the defenders of the town, massacre half of them and threaten to kill the rest unless the defenders surrendered, the third condition would not be met and the act would clearly be immoral.

The final condition is that of proportionality: the good achieved must be greater than the evil results. Presuming that the objective was necessary for the operational success in achieving a victory in a just war, then the cost in civilian lives, while regrettable, cannot be held to be disproportionately evil, and must be accepted as part of the terrible cost of war.

Classical just war thinkers clearly recognise that in battles where there are large civilian populations, the death of innocents will unavoidably result from such an action, and yet that fact in itself cannot serve to render the action unjust. If such were the case, then any battle for a city, such as the hundreds which occurred during the Allied liberation of Nazi-occupied Europe, would be considered immoral, and by logical conclusion any war, at any time, would be immoral. This stand is emphatically rejected by the classical just war thinkers from Aquinas, Suarez and Vitoria, right down through to our own day.

With the previous article on the jus ad bellum, and this article with its consideration of the jus in bello, we have shown the principles which constitute the classical just war theory. We have examined the conditions needed to determine whether a war can be said to have been justly commenced and justly waged. The classical just war doctrine, developed initially by St Augustine and most notably Aquinas, provides us today with one of the most nuanced and rigorous intellectual tools available for rational and principled discussion, and critical evaluation, of questions concerning war and morality.

Return to Oriens home page

Return to Oriens contents page