 Hi, I'm Peter Adamson and you're listening to the History of Philosophy podcast, brought to you with the support of the Philosophy department at Keynes College London and the LMU in Munich. Online at www.historyoffilosophy.net. Today's episode… Onward Christian Soldiers – Just War Theory July 13, 1099 is a date that lives in infamy. It was on this day that the warriors of the First Crusade succeeded in their mission of wresting the holy city of Jerusalem from the hands of the Muslims. What followed was slaughter on an almost unimaginable scale. Thousands of Muslims and Jews were put to the sword. Christian sources on the massacre state that 10,000 people were killed in the Temple of Solomon alone. The slaughter was so great that our men waded in blood up to their ankles. You might say, what else would you expect? Medieval Christian knights were hardly going to show mercy to non-Christians. But consider another infamous date – April 12, 1204. In this climax to the shameful sequence of events known as the Fourth Crusade, Christian warriors who were supposed to be trying to recapture the Holy Land sacked the capital city of the Byzantine Empire. A three-day spasm of murder, rape, and destruction followed. This greatest of the medieval Christian cities would never really recover. Surely though, the Latin Christians wouldn't do this sort of thing on their own territory. Sadly they very much would. Only five years later, on July 22, 1209, the city of Bésier in southern France was sacked in the Crusade against the Cathars. Not only the Cathar heretics sheltering inside, but the entire population of the city was put to death. Supposedly, the papal legate overseeing this horrific event instructed the soldiers, kill them all, for God will know his own. To hear more about these and other shocking events, you can check out the History of the Crusades podcast. Its host, Sharon Eastaw, was one of the medieval podcasters I interviewed some time back. Her series shows that the Crusades against the Muslims and Cathars involved extraordinary levels of violence. Of course, medieval Christians had no monopoly on horrific cruelty in the name of religion in that or any other period, but the Crusades seem somehow special because of their flagrant hypocrisy. We read in the book of Matthew that Christ instructed his followers to turn the other cheek, and for good measure stated that, all they who take the sword shall perish with the sword. How could the atrocities perpetrated by the Crusaders be justified within a Christian worldview? Well, obviously they couldn't, and in fact the sacking of Constantinople and massacre at Beziers were seen as shocking by many contemporary Christians. Yet, there was widespread agreement among medieval Christians that the Crusades were morally justified, even obligatory. More generally, intellectuals of the period gave careful thought to the question of war. The pacifist sentiments of Christ notwithstanding, there were circumstances in which Christians could, and indeed should, take up arms. Despite the religious context, medieval discussions of just war can seem eerily familiar as when we find them wondering whether the use of ultimate weapons can ever be justified, though they meant by this crossbows, not atomic bombs, or what legal conditions need to be satisfied before war can justly be declared. To justify war, you first have the general problem of reconciling violence with Biblical teachings. As the main character of the recent movie, Calvary, puts it, The commandment, Thou shalt not kill, does not have an asterisk beside it, referring you to the bottom of the page where there's a list of instances where it is okay to kill people. Some early Christian intellectuals were inclined to agree. The Latin Church Father Tertullian suggested that no Christian should engage in warfare, while the Greek Father Origen said that believers should fight in good causes, but only with prayer. The decisive influence for the medieval's came, as so often, from Augustine, who argued forcefully that violence can often be justified. The important thing to Augustine's mind was the intention that leads one to engage in warfare or other violence. Though peace is our ultimate goal, even in the midst of war, we are permitted to break the peace temporarily in order to combat and to punish sin to defend the faith with arms as well as words. So, the medieval's generally assumed that war is sometimes justified. How though to determine exactly when and how wars can be fought justly? To answer this question, they looked to the Roman legal tradition. Isidore of Seville summed up the legal standpoint on war as follows, A war is just when, by a formal declaration, it is waged in order to regain what has been stolen or to repel the attack of the enemies. This passage was quoted prominently in the widely read Legal Decretum of the legal scholar Gratian, and thus set the template for pretty much all medieval discussions of war. At the heart of Isidore's definition is the idea that you are always allowed, morally speaking, to defend yourself and your property. This is part of the natural law. Of course, that doesn't mean that whenever you or your property have been attacked you should immediately retaliate with violence. If someone steals one of your books, even a particularly beloved book based on your favorite podcast series, you shouldn't just go over to their place and exact some vigilante justice, you should report them to the authorities. And of course, the medieval legal thinkers were hardly going to encourage people to take the law into their own hands. Violence in general, and war in particular, was justified as a last resort to be used when legal measures could not be brought to bear. An obvious case would be an imminent physical assault on your person. In such a case, you have permission to fight back since there is no time to call in the proper authorities. Similarly, if a king's territory is invaded, he may legitimately unleash his armies to protect his realm. In either case, the violence used against the aggressor is a substitute for the legal sanction that would be imposed if circumstances permitted. Legitimate violence by private citizens or by the state has thus been called an extraordinary legal process by Frederick Russell, who quite literally wrote the book on medieval theories of war. In a real courtroom setting, the punishment must fit the crime. Likewise, our legal authors stressed that legitimate violence must be proportional. If someone slaps you in the face, you're not morally required to turn the other cheek, but that doesn't mean you're allowed to kill him. Sometimes, what counts as proportional is not so easy to determine. If you're assaulted by an unarmed person and you have a weapon, can you use it? Even more difficult is to say how armies should conduct themselves in a war. As in the face-slapping case, the fact that a war is justified doesn't mean that anything goes. The medieval's notions of acceptable military conduct were shaped by ideals of chivalry as well as by the legal tradition, so they worried about the use of powerful but ungallant weapons like crossbows, about the even more ungallant use of deception and ambushes, and about the common practice of despoiling captured cities. A confessional manual written by Johannes de Dao in the middle of the 13th century offered advice concerning these issues to soldiers who feared that they might fall into sin while on campaign. A look through more theoretical literature would have been discouraging to such worried warriors. No less an authority than Peter Lombard judged that any soldier would be bound to sin, while the more optimistic Hugh of Saint-Cher said that the rare individual might manage it. Yet theologians were sometimes remarkably permissive in their attitudes about conduct in war. Unsurprisingly, there was general agreement that heretics could justly be slain. Augustine himself had argued that charity towards sinners could sometimes involve killing them. More surprising is that they permitted at least the unintentional killing of faithful Christians who might be mixed in with the heretics. This isn't quite kill them all for God will know his own, but a medieval knight probably wouldn't be able to tell the difference. Remember though Augustine's point that warfare is justified by the good intention of those who declare the war and fight it. If your aim is really to punish and prevent sin and to restore peace, that in itself should preclude many of the actions we would today call war crimes. A soldier who took this point seriously was bound to wonder what he should do if he was called to serve in an unjust war. Could there be any such thing as a medieval conscientious objector? We may again be surprised to find that the answer is yes. The Dominican writer Roland of Cremona stated that soldiers who were being dragged into an obviously immoral military endeavor should refuse to participate. Yet there was a powerful counterweight to this tendency, namely the medieval relation between vassal and lord. Since a vassal was sworn to give military service to his lord, any refusal to do so had grave moral as well as practical consequences. In addition, authorities like Augustine taught that war leaders had the moral responsibility for unjust wars, effectively absolving the frontline soldiers from the overall sinfulness of the conflict. The general advice to the medieval warrior was, then, to just follow orders. All of this should make it clear that the medieval church was not in the business of trying to stamp out warfare. But of course, the church went further than that. Bishops and popes, sometimes encouraged and in the case of the Crusades, actually launched wars. Here we arrive at another key question. On whose authority can war justly be waged? Clearly a medieval peasant was in no position to declare war, but plenty of feudal lords had well-armed knights at their disposal. There were also those recognized as kings and, at the top of the secular power structure, the Holy Roman Emperor. In parallel to that structure was the church, with the Pope playing a role analogous to the emperor's. And don't forget that the church had extensive land holdings and the ability to flex its own military muscle. In short, there were plenty of people who were in a position to start serious trouble. Who actually had the right to do so? Different legal authors took different views on the matter. One of the most important commentators on Gratian's Decretum, an Italian canon lawyer named Huguizio, suggested that only a secular prince can wage war justly. But just war requires rightful authority, and no medieval author could deny that there is one authority that outranks all others—Gods. Hence, all agreed that the wars fought at God's explicit command in the Old Testament were justified. From here, it was only a short step to seeing the Pope as having legitimate authority to declare war, for the Pope is God's representative on earth. A war launched by the church could even be seen as a version of the War of Self-Defense. It would, quite literally, be fought in defense of the faith. We can find this sequence of thought in Gratian and many of his followers. A particularly clear case was Hostensius, a canonist who was tireless in his efforts to justify the supreme authority of the Pope in such matters, something Russell memorably describes as high theory in the service of low cunning. Hostensius and like-minded lawyers supplied the intellectual rationale for the Crusades, arguing that the Pope was entitled to incite them and also that he could offer genuine absolution of sins for those who took the cross. But how could this be squarried with the idea that just wars need a just cause? The Crusades seem to be a clear case of an unprovoked and offensive war, not a case of self-defense. One possible rationale was that Islam itself, as an apostate religion, was an attack on the Christian faith, reason enough to fight against Muslims wherever they might be found. But this was not the usual justification. Even Hugutio recognized that Islamic states could exercise legitimate sovereignty. Instead, the casus belli, or legal justification for war, was that the Muslims were occupying the Holy Land, which Christians saw as rightfully theirs to control. The upshot is that atrocities or not, the Crusades were seen as satisfying all the standard medieval criteria for just war. It seems clear that they would thus have found approval with the medieval thinker most famous for his views on just war, who was of course Thomas Aquinas. I've been arguing over the past episodes that Aquinas needs to be understood within his historical and intellectual context, and this is never more true than when reading his remarks on warfare. His comments are famous and influential, but surprisingly brief. They take up a single question with only four articles in the Summa Theologiae. Nor is what he has to say very original. He's largely in agreement with the Augustinian legal tradition. One book on the topic goes so far as to say, But that's a bit harsh, because there are several ways in which his discussion is a milestone in just war theory. First, Aquinas brings his characteristic clarity and nuance to the issue. He identifies three criteria by which wars are justified. They must be fought with legitimate authority, for a legitimate reason, and with the right intention. This checklist could withstand philosophical scrutiny even today, and Aquinas makes interesting remarks about each item on the list. Regarding authority, he points out that the reason a private person cannot make war is that he could instead turn to a higher authority. This makes clear an assumption that underlies much of the medieval theory of war. Figures like princes, emperors, and popes have the authority to declare war precisely because there is no legal authority above them, to which they could turn in order to settle disputes. On the issue of just cause, Aquinas connects the usual ideas about self-defense and rectification of injustice to Aristotelian political philosophy. Wars are just when they are waged to defend the common good, the same goal rulers should have in view when they are making laws. Finally, there's a third criterion of good intention. It's here that Aquinas's most philosophically fruitful idea comes in. It's called the doctrine of double effect. The classic text on this is found in his treatment of a question that we've seen to be closely related to the topic of just war. Is it alright to kill an attacker in self-defense? Aquinas says yes, and reasons as follows. It may be that you use force against an attacker solely with the intention of protecting yourself and kill the attacker in the process. The fact that you didn't intend to kill him makes this case very different from one where you deliberately murder somebody. The difference is indeed so large that it excuses you from moral as well as legal blame. In general, we may be justified in performing actions even if they have unwelcome side effects, and the justification turns, at least in part, on the fact that we don't intend those side effects. Aquinas doesn't say a lot about this, nor does he raise it in the context of discussing war, but the relevance is clear. In declaring a war, you pretty well guarantee that soldiers on both sides will be killed, but you do not intend these deaths. In specific military situations, too, double effect comes into play. A much discussed case is where you bomb an area with a civilian population in order to accomplish a legitimate military goal, like destroying a weapons factory. You may be permitted to do so, despite predicting that you'll cause civilian deaths, because killing those civilians is not your goal, but an inevitable and unwelcome side effect. Double effect is also frequently invoked in medical contexts. When a doctor amputates a limb, her goal is saving the patient's life, and even though it will obviously result in the loss of the limb, that is not the doctor's intention. Persuasive though such cases are, the doctrine of double effect turns out to be very difficult to formulate or defend with total precision. For starters, it may seem to give us far too much moral license. Couldn't I just excuse any horrendous consequence of my actions by saying that the consequence isn't one I intended? We wouldn't be very impressed if a government bombed an entire city in order to kill a single terrorist, and then said that the massive loss of life was just a regrettable side effect. But this objection relies on a misunderstanding. Proponents of the doctrine of double effect, like medieval just war theorists, are careful to warn that our actions must be proportionate. In that case though, why do we need the idea of double effect at all? We could just say that a responsible agent should weigh up all the foreseeable consequences of her action, both welcome and unwelcome. If the action has all things considered the best outcome of all the things she could do in her situation, she should perform that action. The answer I think is that the doctrine of double effect is designed for people who don't like to think this way. The idea that you can weigh up all the good and bad consequences striving to get as beneficial a mix as possible is characteristically utilitarian. This way of thinking could, in principle, license you even to form the intention to engage in torture or crusade-style mass murder so long as the consequences are good enough. The double effect theorist is more likely to be someone who thinks that some kinds of action are simply never permitted, at least if they are chosen directly. Taking another person's life would be an obvious example. Intentional murder is a line you just shouldn't cross. The problem is that sometimes we find ourselves in tragic situations where the best available option involves crossing one of these lines. The doctrine of double effect would explain why doing so is morally excusable. The unwanted result is not something you intended, but something you simply couldn't avoid. As Aquinas says, it is only accidentally related to the action you chose to perform. This explanation of the motive for double effect helps explain why it has been so important in contemporary Catholic thought. Notably, the doctrine has been used to explain why even abortion opponents could approve of a life-saving operation on a pregnant woman that will incidentally lead to the death of the fetus. Obviously, this is a rather contentious example, which I don't propose to discuss at greater length here, but I will mention that even in less contentious cases, there are other objections for the doctrine to overcome. Why should our intentions make so much moral difference? Isn't the decisive thing rather what you can reasonably be expected to foresee as the result of what you do? Again, it seems that any action can be described in various ways. The historian says, the Crusaders deliberately went on a mass killing spree slaying Cathars and Christians alike, where the Crusaders themselves would say, we eliminated heresy from the bosom of the community, and sadly a few Christians got killed in the process. From this perspective, double effect looks like an invitation simply to justify your action by describing it in the best possible light. Whether you like it or loathe it, the doctrine of double effect gives us another example of Aquinas's far-reaching, and often surprising, influence in the history of philosophy. And we aren't done with him yet. I'll soon be moving on to the contribution of his controversial colleagues in the Paris Arts Faculty, but I'll be mentioning Aquinas in future episodes, notably when we look at late 13th century developments in metaphysics. Before all that, I want to step back and consider his thought as a whole. For that purpose, I'll be joined by one of the world's leading experts on Aquinas's thought in an interview whose effect will probably be to double your understanding of this legendary thinker. If you're still doubting Thomas, you won't be once you've heard me speak to Scott MacDonald, here on The History of Philosophy, without any gaps.