The Rights of Self-Defence and Justified Warfare in the Writings of the Twelfth- and Thirteenth-Century Canonists

Chapter 5
The Rights of Self-Defence and Justified Warfare in the Writings of the Twelfth-and Thirteenth-Century Canonists

Charles J. Reid, Jr.


James Brundage and I first became acquainted in the spring of 1978, when I enrolled as an undergraduate in his class on the history of medieval law at the University of Wisconsin-Milwaukee. I enjoyed the class so much I did directed research with Jim the following year, exploring the treatment of soldiers’ wills in medieval Roman and canon law. Jim had by this time given me as well an abiding interest in the history of warfare and that most paradoxical of medieval enterprises—the effort to place legal restraints on a process that might otherwise know no boundary. And when, in the 1980s, I organized a series of symposia that concluded in my editing a book on the bishops’ pastoral letter on nuclear arms, I knew to ask Jim to contribute a chapter on the earlier canonistic effort to supply moral guidance to military conduct.1 Modern bishops and medieval canonists, it seemed, had much in common.

This chapter draws on some of my work on the origin of individual rights in medieval law to examine the operation of the related, but distinct, rights of self-defense and justified warfare. To speak of rights in the context of medieval law challenges some old and cherished suppositions. An earlier school of thought had maintained that if rights existed at all in medieval jurisprudence, they were a vague and subordinate concept. Thomas Aquinas, on this account, had created a system of thought based on an objectively just apportionment of goods which was shattered by the invention of subjective rights in the work of William of Ockham or Thomas Hobbes, depending on whom one reads.2

We know now, of course, that the medieval canonists had a full and robust understanding of individual rights. Rights (iura) were seen variously as faculties, powers, liberties, or interests of the individual, and might function as trumps that restrained arbitrary action on the part of those with power.3 Many of these rights, including the rights of self-defense and justified war, were considered natural rights, that is, rights derivable from nature and accessible to all those with reason and good will.4 In this respect, the rights of self-defense and justified war belonged in the same category as the right of the poor to sustenance, the right of married couples to conjugal relations, the right of offspring to claim a portion of parental inheritances, and other claims the justness of which seemed self-evident to the medieval legal mind.

Patristic and Classical Roman Law Background

Medieval jurists confronting the idea of a right of self-defense had to contend with a tradition that had at least in part questioned this proposition’s legitimacy. It seems self-evident that any theory of just war should begin with the right of self-defense, but this was not self-evident to St. Augustine, the source of so much of the medieval just war tradition, who argued that fundamentally there was no right of personal self-defense.

To St. Augustine, one must always prefer the eternal and the spiritual over the transitory and the temporal. Thus one who defended oneself by taking the life of another sinned, since he preferred the preservation of his own transitory, mortal existence over greater spiritual goods, and so almost certainly acted with libido, best translated as excessive desire or passion.5

At the same time, however, St. Augustine was willing to justify the public taking of life by reference to the principles of Christian charity: public officials, properly motivated by Christian love and keeping foremost in their minds the need to maintain public order, might kill in warfare so as to preserve the peace and restrain sinfulness.6

Classical Roman law, on the other hand, began its analysis from the intuitively obvious starting point of self-defense. An excerpt of Florentinus taught that one might properly resist force with force so as to prevent injury and to protect one’s physical well-being.7 Ulpian added that such resistance was licit only if it was done ex incontinenti—“at the time of the attack”— rather than ex intervallo, “after a delay.”8 An excerpt from Paulus pronounced that “all statutes and all iura permit the use of force to defend against force.”9 Iura here might mean either “laws” or “rights.”

A decree of Diocletian permitted the use of “moderate” force in the protection of one’s property.10 A colorfully-worded statement by the Emperors Valentinian, Theodosius, and Arcadius added that all persons had a “free faculty of resisting” intruders with deadly force, since, they reasoned, it was better to resist in this world than to litigate in the next.11 A worldly, earthly pragmatism here trumped the theological. This appreciation for the practical was in keeping, however, with long Roman tradition. As early as the Roman Republican period, Cicero grouped self-defense as among the actions authorized by the ius naturae.12 Resistance, however, had to be proportionate to the threat. As the Roman jurists put it, a moderate self-defense was blameless (moderamen inculpatae tutelae), but an excessive defense counted as murder.13

War, at Roman law, was conceptually distinct from personal self-defense. It required a just cause, a public declaration of hostilities, and carried with it a set of rights and duties incumbent upon the participants.14 War, in the Roman world, was an accepted, even routine part of statecraft, provided the proper forms were followed.15 Indeed, it was even taught by Justinian that war itself was a part of the ius gentium, the law of nations found among all civilized peoples.16

War, according to at least one classical Roman source, was about the restoration of one’s ius. Livy, in describing how war was commenced in the early days of the Republic, stated that one of the fetiales, priests who had among their duties the declaration of war, would announce to the enemy that he had come as a public representative of the Roman people. His task was to call down judgment on the enemy because they had not made proper amends (neque ius persolvere), and so the elders of Rome would now take counsel how their right (ius nostrum) might be restored.17

In this passage one sees Livy moving fluidly between objective and subjective understandings of ius, as war was conceived even in Livy’s day as both a restoration of just order and a restoration of certain public rights. This understanding of war as restorative of just order and injured rights would come to be systematized by the medieval canonists of the twelfth and thirteenth centuries.

The Decretum18 and Decretist Analyses of Self-Defense and Warfare

The Decretum’s treatment of self-defense and war incorporated elements from both Augustinian theology and Roman law.19 Its analysis of personal self-defense contained some potentially contradictory elements. On the one hand, the Decretum includes a decree of the fourth council of Carthage, representing the old suspicion against self-defense, which denied clerical promotion to those who avenged their own injuries.20 This choice of texts, however, was countered with an excerpt from Isidore of Seville who had borrowed from Roman sources to reiterate the point, going back to Cicero, that the repulsion of force by force was a part of the natural law.21 No effort was made to reconcile these passages, which were placed in different parts of the Decretum.

The Decretum’s analysis of justified warfare, however, was more coherently arranged, grouped as it was under the heading of a single causa—Causa 23. This section of the Decretum, which amounts to a small treatise on war, commences with some dialectically arranged biblical propositions. Warfare, it is maintained, is alien to the Gospel.22 The standard texts were mustered to support this conclusion. We must turn the other cheek when struck; we should walk two miles with another when forced to walk one; we should not judge, lest we be judged; and other like texts were deployed to support what seemed like a self-evident proposition: Christians were forbidden to wage war.23

The Decretum, however, follows these passages with some generous samplings of St. Augustine’s argument that the Gospel teachings were merely intended to guide the inward disposition of the heart.24 They did not dictate a policy of pacifism, but only provided a guide to individual conscience. One should be patient and loving even when waging war, but in an imperfect and fallen world, where sinners must still be restrained and the innocent and the vulnerable protected, war cannot be said to be excluded by the Gospel.25

The Decretum went on, in Causa 23, quaestio 2, to consider how a particular war might be said to be just. This quaestio opens with an excerpt from Isidore of Seville which declared war to be just when fought in accord with an edict for the recovery of goods or the repulsion of attack.26 In a seeming aside, the text, as excerpted, added that it was a just judge who spoke ius and decided cases in accord with ius who presumably was qualified to declare war.27 The Decretum subsequently endorsed this encapsulation of the just war in a dictum.28 In this way, one sees the conferral on rightful authority of the responsibility for declaring war and the premising of such a determination on a finding that the order of justice has been violated and must be restored.

The Decretum also contains texts relevant to just war in its first distinctio, part of the “Treatise on Laws.”29 Mention has already been made of the Isidorian text, known as Ius naturale, which grounded self-defense on the natural law.30 A second text of Isidore’s, again epitomizing Roman law, declared war to be a part of the ius gentium.31 In yet another excerpt, Isidore identified the subject-matter of the ius militare, “military law,” as including the solemnities of declaring war, the forging of alliances, the maintenance of martial discipline, and other such matters.32 The Decretum did not comment on either of these latter two excerpts, taking for granted the picture presented of the right to wage war.

A careful reading of the Decretum’s sources, and the manner in which they were edited and deployed, would thus lead a reader to conclude that the right of self-defense was grounded on natural law while the right to wage war was grounded on the law of nations. The decretists who followed Gratian were forced to come to terms with these seemingly contradictory foundations. Over time, in the course of reconciling these varying sources, the decretists tended to collapse the distinction between personal self-defense and the waging of war, while moving away from the Augustinian aversion to self-defense. Indeed, it is clear that the decretists sought to carve out a unified theory of a basic right of self-defense that encompassed both personal acts of self-preservation and justified warfare within the terms of its analysis.

Rufinus, who wrote his Summa on the Decretum around 1160, sought to retain the Isidorian distinction between a natural right of self-defense and a right of war grounded on the ius gentium. Rufinus asserted that the simple repulsion of force by force belonged to the ius naturae because it seemed that nature had taught this much to all animals.33 The vindication of legally cognizable injuries, however, which was the peculiar subject-matter of warfare, belonged to the ius gentium, since only men, not animals, can be said to do or permit injuries.34

By the time one arrives in the 1190s, however, one finds a different picture. The Summa, “Induent Sancti” considered directly whether warfare was in accord with the natural law. It seemed, the anonymous author began, that it is not. Peace is the first teaching of the natural law, as embodied in the Golden Rule.35 The introduction of “dominion” (property, lordship), however, which came into being because of human sinfulness, led to wars, captivity, and slavery. Since man cannot himself dispense from the natural law and thus remained obliged to obey its first precepts, it is clear that God must have dispensed from these first terms, although the Summa’s author is at a loss to know when this dispensation occurred.36 In any event, God did dispense from the natural law’s primitive requirements, and so warfare became a licit activity, in conformity with natural law, provided it is waged justly.37 On this analysis, the author noted, military service is an affirmative good, provided that one acts in self-defense and to keep the peace.38 Indeed, an armed self-defense is a right conceded in our fallen present state to all men by the natural law.39

Johannes Teutonicus made the same point more tersely but equally effectively. He freely allowed that it was possible to repel injuries with force and supported this conclusion with a reference to Isidore’s reliance on the natural law to justify self-defense.40 Johannes proposed that this principle might be so all-embracing as to allow even direct clerical participation in war, although he subsequently qualified this view severely.41 Throughout his analysis, Johannes simply took for granted that he was addressing organized combat, not personal self-defense. Unlike Rufinus, Johannes attached his commentary to Causa 23, not distinctio one.

The right to wage war in some decretist analysis was thought to include self-help. This is illustrated by a gloss of Rolandus’s on the waging of war in order to gain safe passage through third countries. War, Rolandus asserted, is sometimes permitted, even in the absence of jurisdiction and competent authority, where the natural law has been violated.42 The example Rolandus gave was the war waged by the Israelites against the Amorites when the latter group refused to grant the Jewish nation safe passage through their territory.43 In ordinary circumstances, however, Rolandus conceded that those waging war required the potestas inferendi belli, the power to make war, which he associated with jurisdiction.44

In fact, for most of the decretists the authority to wage war was a fundamental part of their analysis of a given war’s justice. Rufinus argued that war should not be counted as a sin where it was just and waged at the direction of “public powers.”45 The Summa parisiensis pronounced as just those wars waged by princely edict against publicly determined enemies for the recovery of goods or the vindication of injuries.46 A war waged without princely authority is “without doubt unjust.”47 The Summa “Elegantius in iure divino” forbade the taking up of arms on private authority (sua auctoritate), admonishing that this could be done only by the “public power” (publica potestate) of the ruler.48 St. Augustine, the Summa’s author reasoned, required as much when he recognized the “authority to wage war” (“suspiciendi belli auctoritatepenes principles”) was given princes in order to preserve the peace.49

This authority came to be denominated the right to wage war. Thus Alanus Anglicus spoke of the “right of waging war” (ius indicendi belli) that belonged to princes. Alanus included among the princes who had this power even some who had nominal superiors, such as the rulers of northern Italian communes.50 Other texts, such as the Summa “Induent Sancti”51 and the Glossa ordinaria to the Decretum52 spoke of the “right of the sword” (ius gladii) which belonged to princes.

The Decretalist Analysis of the Rights of War

The decretalists who commented on the steady stream of papal decretal letters which issued forth from the papal chancery in the late twelfth and thirteenth centuries adopted as their own the decretists’ battery of ideas and vocabulary when analyzing the question of the licitness of war. Raymond of Peñafort, synthesizing the preceding debate, proposed that a war might be just provided five criteria were satisfied: war must be directly waged by secular rulers, not ecclesiastical ones; it must have as its object the recovery of goods or the defense of the homeland (patria); its end must be peace; it must be fought not from a spirit of domination, hatred, or vengeance, but out of a spirit of love, justice, and obedience; and its authorization must come either from the prince, or from the Church, when it acts to defend the faith.53

Raymond also asked whether in the absence of princely or ecclesiastical authority the natural law might serve as grounds for waging war.54 He answered by distinguishing between an attack on persons and an attack on property. A defense of one’s person is allowed, provided one is genuinely threatened with lethal force and the resistance is proportional.55 Raymond was also willing to tolerate a forceful defense of property, provided the defense was “immediate” (in continenti).56 “Vengeance,” however, was not tolerated either in the defense of one’s person or property, and was to result in excommunication.57

The decretalists, like the decretists, also employed rights language to analyze the authority by which rulers waged war. Innocent IV’s analysis of this question makes clear the role played by rights in the decretalist treatment of war.58 Innocent identified three levels of violence, each of which demanded separate analysis.59 It is permitted to all persons, Innocent observed, to wage war (movere bellum) in defense of one’s persons and things, although such action is not properly called war but “defense” (defensio).60 One does not require princely authority to act in self-defense, provided one acts at once; rather, one acts on the authority of ius itself.61 (Ius in this context clearly meant the power to act in conformity with the requirements of a transcendent natural law—a neat combining of subjective and objective elements of “right” that is impossible in English but that regularly occurs in the Latin of ecclesiastical jurists).

But what of the person whose property has been taken and is unable to prosecute his claim (ius)? It is everywhere permitted in these circumstances to rely upon the authority of a superior who will take up arms on one’s behalf and wage war so as to recover what has been taken.62 But where the authority to whom one has had recourse himself has a superior—as Innocent puts it, where he has a prince over him—then action may only be taken where the ultimate superior has consented. Innocent resorted to rights language to explain this layered relationship: such an arrangement seemed just, Innocent reasoned, since it is permitted to no one to tamper with rights without the permission of the source of those rights.63 The prince’s rights must not be put in doubt by the unauthorized actions of a subordinate.

Innocent then turned to the third type of conflict—war waged by a lord with the right to wage war (ius indicendi bellum). A prince who has no superior is always able to wage war against the subjects of another prince who have provoked the attack.64 This right, Innocent noted, even belonged to prelates who held temporal jurisdiction, who, although forbidden to engage directly in hostilities, might prosecute war and exhort their troops to fight the enemy and capture them, but not command their deaths.65 This last distinction was no doubt lost on many of the bishops who exercised temporal jurisdiction.66

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