Abstract
A survey of just war theory literature reveals the existence of quite different lists of principles. This apparent arbitrariness raises a number of questions: What is the relation between ad bellum and in bello principles? Why are there so many of the former and so few of the latter? What order is there among the various principles? To answer these questions, I first draw on some recent work by Jeff McMahan to show that ad bellum and in bello principles are not, as often portrayed, independent—the justice of conduct in war largely presupposes the justice of the recourse to war. Undermining this independence claim is one important step toward revealing the unified logical structure of just war theory. I then argue that we can see the dependence of the jus in bello upon the jus ad bellum, not just in the content of certain principles, but also in the structure of the two sets of principles: I construct a one-to-one mapping between ad bellum and in bello principles. In doing so, I argue also that the shared structure successfully finds place for the questions central to the evaluation of the morality of war: what is a sufficient provocation to use force, what objectives may be sought by force, why or for what ends, who has authority to decide to use force, and when or in what circumstances? Despite variations in expression, the theory allows for a coherent and comprehensive evaluation of morality in warfare.
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Notes
By column, these principles and their ordering are excerpted from: Johnson (1999, pp. 28–29), Hartle (2004, pp. 96–97), Hurka (2005, pp. 35–36) and Orend (2005, Sects. 2.1 and 2.2) (see also Orend 2006 for a much more detailed treatment). Michael Walzer’s absence from this survey is due to the fact that in his seminal work, Just and Unjust Wars, he does not organize his thinking around a list of principles in the way many others do (although I think it is possible to discern there the presence of all the traditional principles, with just cause and discrimination being especially prominent).
Cook, for example, includes both aim of peace and public declaration as separate ad bellum principles in (Cook 2004, pp. 28–31).
Kemp is a notable exception, arguing in Kemp (1988) for a correspondence between ad bellum and in bello principles. Although I agree with much of what he argues, our projects are quite different in detail. Most notably, his reconceptualization centers, not around the five questions I have raised, but around the idea that both jus ad bellum and jus in bello involve substantive (just cause), procedural (proper authority), and internal (right intention) principles, and that other principles like proportionality can be annexed to these.
See McMahan, “Proportionality,” Chapter 5 of an unpublished book manuscript, McMahan forthcoming. Professor McMahan has given me express permission to cite this manuscript, but has asked me to note that it will likely undergo some further revisions prior to publication. Accordingly, wherever possible I rely on what he has already published, especially McMahan (2009), which covers some of the same ground (although it focuses on the jus in bello, while the forthcoming manuscript also devotes substantial attention to the jus ad bellum).
McMahan writes that “what makes a person morally liable to force or violence that is necessary to eliminate an unjust threat is moral responsibility for initiating or sustaining the threat (or perhaps, in some cases, for failing to eliminate the threat)” (McMahan 2004, p. 72). As he later puts it, “moral responsibility for a wrong, particularly an objectively unjustified threat of harm,” is “necessary for liability to attack in war” (McMahan 2009, pp. 34–35; emphasis provided).
McMahan (2004, p. 699). See Sections VI & VII, especially pp. 721–722, for his discussion of liability and discrimination. We may wish to qualify our acceptance of his claim here by insisting that your “defensive attack” be proportionate to the unjust threat posed by your attacker. McMahan explicitly acknowledges this in his forthcoming book under the heading of a “narrow” proportionality requirement implicit in the notion of a just cause, and I discuss this below. See also his illustration of narrow proportionality in his discussion of the case of Bernard Goetz, the man who shot four other men threatening to rob him in a New York subway (McMahan 2009, 20–21).
McMahan, I think, is committed to this possibility by his acceptance of the notion of wars that are “morally justified yet unjust;” see McMahan (2005, pp. 15–16) (see also McMahan 2009, pp. 27–28, where he says that it is “at least possible” that such a war could have a “lesser-evil justification,” but that this is “unlikely in practice”). These are wars that are fought without a just cause but that are necessary to avoid extremely bad consequences (this can be seen as an ad bellum counterpart to Walzer’s Supreme Emergency Exemption to the in bello principle of discrimination). The converse implication, that accepting the possibility of meeting the wide proportionality absent a just cause commits one to the acceptance of morally justified yet unjust wars, does not hold.
Cf. McMahan (2004, p. 709). I should note that McMahan goes onto qualify this—soldiers fighting a war without any just cause for the war as a whole may in some cases have a sort of localized just cause for particular acts of war, such as stopping the enemy from carrying out a massacre of civilians; this would enable them, in such situations, to fight proportionately (McMahan 2004, pp. 712–713). Later McMahan gives the effective example a hypothetical Japanese pilot shooting down the Enola Gay as an instance of this, and allows for other factors that make it theoretically possible for unjust combatants to fight proportionately, such as defending their country’s civilians from the collateral effects of enemy operations (see McMahan 2009, pp. 16, 26).
McMahan insists upon this in his forthcoming manuscript, holding for example that the requirement of in bello proportionality cannot be met “unless military victory would have an objective positive value.” In his recent book McMahan makes a similar point: contribution to bringing about all, but only, “genuinely good effects” (he mentions the liberation of women from oppressive circumstances) may count in a wide proportionality calculation (see McMahan 2009, p. 26).
Hurka (2005, p. 45). Largely for the McMahanian reasons adduced above, I think this is too strong a claim.
Hurka writes of “the dominant view in the just war tradition, which treats the jus in bello as entirely independent of the jus ad bellum” (Hurka 2005, p. 44); McMahan as we saw takes the independence of the two sets of principles as a foundational tenet of traditional just war theory (cf. McMahan 2004, p. 694).
Russell (1975, p. 155): The Decretalists were canon lawyers who commented on Papal decretals in the late twelfth and thirteenth centuries. Their number included such figures as Hostiensis and Innocent IV.
See for example de Vitoria (1991, q2aa2–3, pp. 306–312).
Cf. Hurka (2005, p. 45), and McMahan (2004, p. 730) and McMahan (2009, chapter 3). Although McMahan is a bit more sanguine about individuals assessing ad bellum considerations, he does seem to agree with Hurka that soldiers are not to be held legally culpable merely for fighting. Their conclusions do differ in some subtle but important ways; ways, however, that we may bracket here.
I say seem to make plausible because I do not think the moral evaluation of any human activity can ignore the questions of what, about what, why, who, and when. Why has jus in bello thinking historically focused overwhelmingly on discrimination and proportionality (which as I will show address the what, about what, and when questions)? I believe it is because the answers to the why and who questions (ends and authority) are largely determined and dictated to soldiers by others. Practically speaking, emphasis on discrimination and proportionality has been much more important in restraining violence in war. But as I will argue, the principles addressing the other questions remain important.
Comparative justice is sometimes also mentioned, although its status is contentious (see e.g., McMahan 2005, pp. 19–20). Here I will just note that if one accepts it, it should be seen as an amplification of the principle of just cause. Again, one sometimes sees public declaration included. This requirement, if it is one, does not seem to me to be of sufficient importance to be accorded status similar to that of the traditional principles. But if we did want to include it, I think it should not be seen as self-standing, but should be annexed to proper authority (as partly specifying how the authority to wage war should be exercised). This is in effect what Orend does in Orend (2005). Finally, we may want to insist that accord with international laws and treaties governing recourse to war is an important, if defeasible, ad bellum consideration. If so, it too could be annexed to proper authority, as helping to define which sorts of government (those of states, local unions, or the United Nations) have the authority to wage which kinds of war (wars of national defense or humanitarian intervention, e.g.).
Johnson (1999, pp. 41–44). For Aquinas’s discussion see his Summa theologiae, IIa-IIae, q40a1.
McMahan’s “narrow” proportionality requirement, which he sees as implicit in the principle of just cause, offers one promising way of assessing whether the just aim is, in my terms, “sufficiently grave.”
de Vitoria (1991, q3a1, p. 314). As he clarifies elsewhere, the “injury” must not be of a trivial nature due to the “cruel and horrible” nature of the effects of war [cf. q1a3 (p. 304)]. McMahan makes a similar point: “the just causes for war are limited to the prevention or correction of wrongs that are serious enough to make the perpetrators liable to be killed or maimed” (McMahan 2005, p. 11).
I might also note that, once one has a just cause, there is surely nothing wrong with intending to secure certain good effects of the war that could not count as causes for war but could weigh favorably in what McMahan calls a wide proportionality requirement (e.g., better diplomatic and economic relations with partners in a coalition), although there will be constraints on how one may pursue such effects.
See Johnson (1999, p. 43), for a brief discussion of justifiable exceptions to secondary principles. Johnson mentions the resistance to the Germans by the Poles, Dutch, and Belgians at the outset of the Second World War. Arguably, such resistance had no reasonable hope of success and was disproportionate in causing deaths that could have been avoided by an earlier capitulation, and yet justified. Of course, one might prefer to say that one must meet these requirements, but that success need not be defined in terms of victory on the battlefield: perhaps significant resistance to evil or delay of an enemy advance that may help others are important goods relevant to these calculations—an interesting issue but not one needing to be settled here.
The “roughly” is important: Hurka’s article provides a penetrating investigation of what sort of goods may count, and what sorts of evil; McMahan’s (2009 and forthcoming), with their distinction between narrow and wide proportionality, provide another valuable perspective.
See Hurka (2005, pp. 37–38). The quotation is from p. 37.
Along these lines, Kemp has argued in his (1988) that last resort should instead be annexed to just cause, on the grounds that one does not have a cause for war while peaceful options remain available. I want to resist this annexation too. The fact that one has a just cause for war does not yet mean that in resorting to war one will be justified—other conditions must also be met, and last resort is one of these. I think it is best to keep distinct the legitimate aims and provocation of war, on the one hand, and the other conditions that must be met before it is right to react to this provocation and pursue these aims by means of war on the other.
I do not, of course, mean to deny that there will be some point during which this balance is shifting at which the statesman must reason that, although he could wait still longer, the cost of doing so is growing too great. If one tries to wait until the moment that is truly “last,” one will likely find that one has waited too long [This sort of consideration explains why Anthony Hartle calls this principle, instead, the reasonable exhaustion of peaceful remedies (cf. Hartle 2004, pp. 96–97; cf. also Walzer 1992, pp. xiv–xv)].
A historical aside that may be of interest, given the medieval pedigree of the just war tradition: The questions what, about what, why, and who (formal and material just cause, right intention, and proper authority) correspond, respectively to formal, material, final, and efficient causality. The primary principles of the jus ad bellum specify the “four causes” of the just war. One example of a medieval evaluation of action in terms of precisely the five questions I have focused on (including the when question about the circumstances of action), albeit one not addressing war or the four causes explicitly, is found in Aquinas’s remarks on Aristotle’s treatment of ignorance in action; see Aquinas (1993), Book III, Lecture iii.
Two examples of attacks directed toward illegitimate objectives (certainly at least if they are intended to have lethal results): An attack whose primary purpose was to test a new weapons system; an attack whose primary purpose was to intimidate potential future rivals. Arguably, the fire bombing of Dresden in early 1945 was aimed in large part at “impressing the Soviets (on the eve of the Yalta conference) with the power of the Allied strategic air forces” (Biddle 2002, p. 254)—of course this attack was already (materially) indiscriminate; my point is that if it did have this objective, it was also formally indiscriminate, and would have been so even if its targets were military in nature.
I discuss a principle of “graduated discrimination” that seeks to help answer this question in Toner (2004), and there maintain that in some cases civilians may be targeted. Thinking along these lines is not unique to me. Anscombe (1981, p. 53) and Murphy (1986, pp. 346–347), e.g., both concede that the range of acceptable targets includes those, not in uniform, who nevertheless contribute directly to the war effort. McMahan accepts the idea of “noncombatant liability,” going so far as to maintain (plausibly, I think, given his description of events) that the executives of the United Fruit Company who “persuaded the Eisenhower administration to organize and direct a coup that overthrew the democratic government of Guatemala…were liable; they were legitimate targets” [McMahan (2004, pp. 725, 726); see also McMahan (2009, Chapter 5), especially pp. 221–223 for a more nuanced presentation of this position].
Modern strategic theory conceives the enemy to have certain “centers of gravity,” key systems the destruction of which will eliminate the enemy’s will and ability to fight on. Among these centers are infrastructural elements such as power, communications, and transportation. To the degree this theory is correct, it begins to seem in principle possible for one state to destroy another state (in its capacity as a rival military power) without killing anyone. This is still a dream, and of course the destruction of infrastructure tends to have secondary effects that can result in civilian deaths in large numbers (just consider the effects of a loss of power on hospitals or nursing homes). This strategic theory and many of its moral implications are discussed in Cook (2004, Chapter 8). Worth noting here, though, is the fact that discrimination plays an important role in infrastructural target selection too: Does this target have a purely military use, or is it “dual-use,” supporting peaceful civilian activities as well? If so, can we justify attacking it by appeal to the principle of double effect?
Johnson (1999, p. 212); the quotation, cited on p. 211, is from Augustine’s Letter to Boniface. Johnson credits, on p. 213, the United States Conference of Catholic Bishops for re-introducing the principle of right intention to the jus in bello in their The Harvest of Justice is Sown in Peace.
See also Orend on this (Section 2.1 of Orend 2005). Yet this is perhaps too strong. As McMahan (personal communication) points out, the law does sometimes take intention into account: “In the Nuremburg ‘ministries’ trials, the industrialists were acquitted because the prosecution was unable to prove mens rea—that is, they couldn’t show that those men intended their acts to contribute to a war of aggression.” But it remains the case that the law of war does not touch the sort of case I mention below, namely one in which a soldier, in the line of duty, kills an enemy combatant, but does so with the intention of taking revenge on, say, “any Iraqi” (that he can get away with killing). Such an action would be legal, but immoral.
This claim fully spelled out would require certain qualifications: For example, it is hardly to be expected that such intentions as achieving legitimate objectives in service of just war aims should always be present in combatants’ minds. Perhaps it is enough that combatants intend to follow what they believe to be lawful and moral orders. Also, some acts of war may be, in terms of intention, neither just nor unjust, but simply excusable.
Of course, the competent prosecution of a war requires initiative at all levels, and therefore requires allowing subordinates a good deal of autonomy. Still, soldiers can be justified in their acts of violence only when operating within the intentions of the lawful command structure. This is the rationale behind, e.g., issuing clear rules of engagement—to set out the parameters within which soldiers may follow their own judgment.
Here let me remark that just as we might wish to annex to the ad bellum principle of proper authority a requirement to honor treaties and international laws governing recourse to war, so we might wish to annex to the principle of lawful command structure a requirement to fight in accordance with the law of armed conflict [to include honoring treaties concerning the treatment of prisoners and the banning of certain weapons—requirements Orend includes in his list in Section 2.2 of his (2005)]. As with its ad bellum counterpart, the importance of such a requirement would be real but limited: Fighting in accordance with the law of armed conflict would of course not be sufficient to ensure that one is morally justified in fighting; nor would it always be strictly necessary, for sometimes morality allows setting positive human laws aside—surely, for example, there is no absolute moral rule against shooting nails out of a rifle when low on ammunition.
Of course, commanders are typically ordered to undertake a certain mission, but they have considerable autonomy in determining just how they shall undertake it, what specific objectives to pursue, and so forth; here is where there is considerable room for military discretion to operate. It may operate also in disobedience to orders judged immoral on the grounds of extreme stupidity.
An example of an action failing the test of military necessity might be the destruction of an enemy position in circumstances in which the position could simply be circumvented, or in which the enemy combatants defending it were likely to surrender if offered the chance.
References
Anscombe, Elizabeth. 1981. War and murder. In Anscombe, Elizabeth Ethics, religion, and politics, 51–61. Minneapolis: University of Minnesota Press.
Aquinas, St. Thomas. 1993. Commentary on Aristotle’s Nicomachean ethics (trans: Litzinger, C.I.). Notre Dame: Dumb Ox Books.
Biddle, Tami Davis. 2002. Rhetoric and reality in air warfare. Princeton: Princeton University Press.
Cook, Martin. 2004. The moral warrior. Albany: State University of New York Press.
de Vitoria, Francisco. 1991. On the law of war. In Francisco de Vitoria: Political writings, ed. Anthony Pagden, and Jeremy Lawrance, 293–327. Cambridge: Cambridge University Press.
Detter, Ingrid. 2000. The law of war, 2nd ed. Cambridge: Cambridge University Press.
Hartle, Anthony. 2004. Moral issues in military decision making, 2nd ed. Lawrence: University Press of Kansas.
Hurka, Thomas. 2005. Proportionality in the morality of war. Philosophy & Public Affairs 33: 34–66.
Johnson, James Turner. 1999. Morality and contemporary warfare. New Haven: Yale University Press.
Kemp, Kenneth. 1988. Just-war theory: A reconceptualization. Public Affairs Quarterly 2: 57–74.
McMahan, Jeff. 2004. The ethics of killing in war. Ethics 114: 693–733.
McMahan, Jeff. 2005. Just cause for war. Ethics and International Affairs 19: 1–21.
McMahan, Jeff. 2009. Killing in war. Oxford: Oxford University Press.
McMahan, Jeff. Forthcoming. The right way to fight. Oxford: Oxford University Press.
Murphy, Jeffrie. 1986. The killing of the innocent. In War, morality, and the military profession, 2nd ed, ed. Malham Wakin, 341–354. Boulder: Westview Press.
Orend, Brian. 2006. The morality of war. Peterborough: Broadview Press.
Orend, Brian. 2005. War. Stanford Encyclopedia of Philosophy.
Russell, Frederick. 1975. The just war in the middle ages. Cambridge: Cambridge University Press.
Toner, Christopher. 2004. Just war and graduated discrimination. American Catholic Philosophical Quarterly 78: 649–665.
Walzer, Michael. 1992. Just and unjust wars, 2nd ed. New York: Basic Books.
Acknowledgments
Work on this article was assisted by a research grant from the Aquinas Chair in Philosophy and Theology at the University of St. Thomas. Earlier drafts were presented to the faculty of the United States Air Command and Staff College and to the philosophy departments of the United States Air Force Academy and Mount Saint Mary’s University, and I received helpful comments from all these audiences. I wish also to thank the editor of The Journal of Ethics and an anonymous referee for help with the penultimate draft. Finally, I owe special thanks to Professor Jeff McMahan for extensive and vastly helpful comments upon an earlier draft, and for granting me permission to draw on part of the unpublished manuscript of his forthcoming book, The Right Way to Fight.
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Toner, C. The Logical Structure of Just War Theory. J Ethics 14, 81–102 (2010). https://doi.org/10.1007/s10892-010-9072-0
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DOI: https://doi.org/10.1007/s10892-010-9072-0