The Just War

Arthur F. Holmes
May 7, 2004

To call war anything less than evil would be self-deception. The Christian conscience has throughout history recognized the tragic character of war. The issue that tears the Christian conscience is not whether war is good, but whether it is in all cases entirely avoidable. This is largely a policy question: In the face of such outlandish evil, how should Christians act? Of course they should seek to remedy injus­tice, to prevent conflict, to avoid bloodshed, to alleviate suf­fering; but should they under some conditions go so far as to actively support military action and participate in the fighting? Is it ever better to fight than not to fight? Could participation in war perhaps be a lesser evil than allowing aggression and terror to go unchecked and unpunished?

Prelude to the Debate

This is a complex issue, and in approaching it we must make certain preliminary matters clear. First, not all evil can be avoided. Evil is not just an individual’s problem, nor is it confined to deeds and thoughts: it is a pervasive condition of fallen human existence that riddles the political and social reality with which we are forced to contend. Real life situa­tions are so twisted and perverted that often no altogether good option remains. We are trapped in moral dilemmas whose roots lie in the past as well as the present, such that whatever we do involves us in evil of some sort. There is no easy way out. To let violence and aggression go unchecked does not eliminate the evil, nor does it leave me unimplicated if I could do some­thing about it.

When faced with a moral dilemma such that any action I take (including the avoidance of action) has evil results, it is not enough to weigh consequences. Right and wrong are not just a matter of the good or evil we produce. They involve both act and intent. An act may be right, and be performed with right intent, and still have evil consequences.

Second, we must be clear that an ethical position, such as the just war theory or any alternative to it, is an ideal that is normative for all people as to how they ought to act and what they should intend. It is not a description of how in fact people have hitherto acted or what they have intended, nor of how they are likely to behave. It is a norm by which to judge actions and intentions, a standard to be appealed to in moral persuasion and to be implemented by whatever legislative or other morally proper means are available. It is not therefore a valid criticism of the theory to point out the blatant disregard of it by medieval Crusaders or by both sides in World War 2 or in Vietnam. People disobey the Ten Com­mandments, too, but that does not invalidate God’s Law. We cannot judge an ethic by people’s failures.

As with any ethic, the just war ideal is intended to be uni­versally binding. The Christian does not have a double stan­dard – one for Christians and one for others. God’s moral law applies to all people everywhere, and all are held accountable (Rom. 1-3). The question, then, is not whether a Christian may fight, but whether anybody at all may fight. Of course, the Christian may still choose to go a second mile beyond what is obligatory, as is done by “vocational pacifists” who claim that Christians have a calling different from others in regard to political and military involvement. But that is a vocational claim not an ethical one, and the person called thereby to nonviolence cannot label all soldiering as ethically wrong.

Third, the just war theory does not try to justify war. Rather it tries to bring war under the control of justice so that, if consistently practiced by all parties to a dispute, it would eliminate war altogether. It insists that the only just cause for going to war is defense against aggression. If all parties adhered to this rule, then nobody would ever be an aggres­sor and no war would ever occur. The basic intention of the just war theory, then, is to condemn war and to prevent it by moral persuasion. But since people will sometimes not be so persuaded, it proceeds to limit war – its occasion, its goals, its weaponry and methods – so as to reduce the evils that have not been altogether prevented.

Fourth, the just war theory insists that private individuals have no right to use force. That prerogative is rather en­trusted to governments in the needful exercise of their duty to preserve peace and maintain a just order. The question to be faced, then, is strictly speaking not whether an indi­vidual, Christian or otherwise, may fight, rather it is whether government ever has the right to engage in armed conflict and whether one should participate as an agent of govern­ment in such conflicts. The answer will depend in part on how one views the political responsibilities of Christians. If Christians may properly participate in governmental tasks, and if limited uses of force are legitimate for governments, then prima facie it is right for the Christian to participate in such uses of force.

Justice and War

With these preliminaries completed, we can turn to a fuller statement of the just war view. This can best be given by means of the following rules which spell out the application of justice to war.

  1. Just cause. All aggression is condemned; only defensive war is legitimate.
  2. Just intention. The only legitimate intention is to secure a just peace for all involved. Neither revenge nor conquest nor economic gain nor ideological supremacy are justified.
  3. Last resort. War may only be entered upon when all negotiations and compromise have been tried and failed.
  4. Formal declaration. Since the use of military force is the prerogative of governments, not of private individuals, a state of war must be officially declared by the highest authorities.
  5. Limited objectives. If the purpose is peace, then un­conditional surrender or the destruction of a nation’s eco­nomic or political institutions is an unwarranted objective.
  6. Proportionate means. The weaponry and the force used should be limited to what is needed to repel the aggression and deter future attacks, that is to say to secure a just peace. Total or unlimited war is ruled out.
  7. Noncombatant immunity. Since war is an official act of government, only those who are officially agents of government may fight, and individuals not actively contributing to the conflict including POW’s and easualties as well as civilian nonparticipants) should be immune from attack.

As we shall see later, these rules pose problems of inter­pretation and application to modern warfare. Their immediate impact is to place severe limits on war that would pre­vent its lapsing into barbarism. Underlying them is a history of ethical, political and legal theory that has developed over the past twenty-four hundred years in the West and nearly a thousand years more than that if one takes biblical history into account. That the just war tradition reaches into both biblical and Graeco-Roman sources should not surprise us, for two reasons. First, the same is true of other aspects both of Western culture and of Christian theology—Graeco-Ro­man forms of thought have provided the vehicle of expres­sion for a Judeo-Christian understanding. Second, while Scripture is the final (that is, decisive) authority in matters of faith and practice, it is neither the only nor an exhaustive source of knowledge about moral matters. Scripture (for ex­ample, Rom. 1-3) makes plain that general revelation attests to our moral responsibilities, and the apostle Paul indicates that some kinds of acts are “contrary to nature.” Many Chris­tian writers, including some of the Reformers, identify the Old Testament Decalogue with a natural law written into the created order and the nature of humanity.

These two roots – the biblical and the natural law – underlie the just war ethic. We shall look at them first separately and then as they combine in the thinking of some later pro­ponents, from Augustine to the present.

Biblical Teaching

The first biblical datum to consider is the sixth command­ment. But by itself it does not help us sort through the com­plexity of the war issue. The Decalogue consists of general rules that are applied in their larger biblical context to con­crete situations. The historical context was Israel’s escape from Egypt and journey to Canaan, during which military action was a harsh fact of life. In the Mosaic Law as a whole, capital punishment was allowable for at least ten different crimes, and killing in self-defense was not a criminal offense. “Thou shalt not kill” cannot therefore be taken to rule out all killing, let alone war.

The key passage is rather Romans 13:1-7. Here the right to use arms is accorded to the civil authorities inasmuch as they are divinely commissioned to restrain and punish evil­doers (1 Pet. 2:13-14). The passage pertains directly to mat­ters of criminal justice and the civil order and only by extrap­olation to international conflict. But it does make clear that for some purposes, the precise scope of which is not defined, government has the right to use lethal force. The context concerns the law of love with its repudiation of vengeful action, its concern for those who suffer, including one’s enemies, and its pursuit of peace. Any use of force, then, must be kept within these limits: it can be neither vengeful nor vicious, it must be merciful, and it must seek a just peace for all concerned.

These limitations are reinforced when one considers the Old Testament attitude toward war. While military conflict is regarded as a tragic fact of life, one for which God strength­ens his people and one which God uses in the execution of justice, it is nonetheless lamented as an evil from whose scourge humanity must be delivered. Israel was instructed to limit the destruction and violence involved in its conquest of Canaan (Deut. 2). David was not allowed to build God’s temple because he was a man of war (1 Chron. 22:8-9; 28:3). The psalmist grieved over violence, looking to the God who makes war cease and destroys its weaponry (Ps. 46; 120). The prophets condemned its fratricide and its atrocities (for example Amos 1‑2), mourned its destruction (Lam.), and gloried in the One who will finally bring peace and justice to earth so that none need even feel afraid (Is. 2:1-5; 9:1-7; 11:1-9).

The New Testament does not address the use of military force as directly as does the Old. It predicts war in the last days, but its moral teachings generally address individuals and churches rather than the governments and rulers that are the Old Testament’s concern. Jesus told Peter to put away his sword (Jn. 18:1-11), for instance, and taught his dis­ciples not to resist evil (Mt. 5:38-48). But this has to be under­stood in the context of what Romans 13 and analogous pas­sages teach. Whatever broader application Jesus’ words to Peter may have, plainly they do not deny to government all uses of the sword. The New Testament does teach indi­viduals not to use violence, and Peter was forbidden its use in religious causes (see also Jn. 18:36). Some Christians therefore repudiate any individual right to use force, even in self-defense, confining it to governmental control of evil­doers.

On this basis the biblical picture is as follows: (1) The use of force in resisting and punishing violence is entrusted to governments. (2) Believers in both Old and New Testaments are involved in governmental uses of force. (3) Such uses of force are to be drastically limited to what is necessary in securing peace and justice. (4) Vengeance is thereby ruled out, along with all aggression; love and mercy must temper justice.

This biblical picture basically supports the just war the­ory. But not all Christians will agree with this picture for two reasons. First, because of disagreement over the rela­tionship between Old and New Testaments. Generally, the Christian pacifist appeals to the New, which in his view takes us beyond the precept and example of the Old to a law of love. The just war theorist, however, is apt to see the law of love in the Old as well as the New, so that the New fulfills, reinforces and interprets the Old rather than superseding it. The law of love is a reaffirmation of the underlying spirit of the Old Testament Law, at one with the spirit of justice rather than in conflict with it. Love as well as justice re­quires action to protect the innocent and to repel and deter aggression.

The second reason is disagreement over whether and to what extent the Christian should participate in government and its exercise of force. Christian pacifists in the Ana­baptist tradition usually hold a doctrine of two kingdoms or two vocations: the earthly or political vocation and the heavenly or spiritual one. Christians have their citizenship and calling in the latter. For some this has meant no political involvement at all; for others it has meant limited involve­ment. In either case, refusal to serve in the military is based here. Christian just war theorists, on the other hand, usually hold that the spiritual is to pervade and transform the politi­cal and other earthly tasks. They therefore have a mandate for full participation in all morally legitimate governmental functions, including military action.

These two issues represent the watershed between two markedly different theologies, so that wherever classic Ana­baptist (including Mennonite) theology prevails, pacifism usually results; and wherever Reformed or Thomistic, or frequently Lutheran, theology prevails, cautious participa­tion in government and in limited war is allowed. Disagreement about war, then, is not just a disagreement about the meaning of some biblical texts. It relates to entire theologies and resultant views of the Christian’s place in society.

Graeco-Roman Sources

Christians are not alone in having a conscience about war. Plato, both in his Republic and in the Laws, urges limits on war, especially in fighting among the Greeks, and insists that the only legitimate purpose of war is the restoration of peace. Aristotle, likewise, arguing that the very nature of man calls for a rule of reason rather than of passion or vio­lence, limits war to what is necessary for peace. Cicero, the Roman jurist, developed this position at considerable length in connection with his ideal of a state ruled by reason’s laws. Nature has endowed man with a desire for peace and order and with the power of reason that makes possible an ordered society. True law is right reason in accordance with nature. It is unchanging and universal. It summons us to duty even to our enemies; it precludes treachery; it requires that even war be governed by moral law.

The rules of war Cicero articulated were the first explicit formulation of just war rules such as we enumerated above, but with some marked differences from Christian versions. In the first place, Cicero defines a just cause as the defense of honor as well as of peace and justice. He thinks it legiti­mate to revenge a dishonor. Later Christian versions reject this and confine just cause to the defense and restoration of peace. In the second place, while Cicero talks of humane treatment, Christian writers go further and require merciful treatment of enemies. These differences arise from the fact that while Cicero’s just society is ruled by natural law and reason, the Christian concept of justice is pervaded by a con­cept of a love, even for one’s enemies, that goes the second mile. This rules out vengeance and unconcern.

Christian Developments

Augustine, writing in north Africa shortly after A.D. 400, recognizes a natural law as well as a biblical mandate both to governments to defend peace and order and to individuals to love their enemies. And he roundly criticizes Cicero’s ideal state for failing to render to God his right: how then could it be a just society? Men are ruled in any case by what they love, not by reason and its knowledge of natural law alone. But Augus­tine is also realistic about the twistedness of the human condition. It is not often the case that one side is altogether in the right and the other side altogether in the wrong. Nor is it the case that soldiers are always able to be ruled by reason or by love, for passions are excited and the best of moral rules and intentions may be violated. While he endorses just war ideals qualified by love, then, Augustine advises the Christian who goes to war to repent in advance, because the ambiguities of the situation confuse moral issues and because passions confuse the moral intention. He tells the Roman General Boniface, who was later to defend Carthage against the Vandals, that war is not a matter of choice but of necessity, forced on us by the need to control violence in a fallen world. It is waged only to restore peace, so he should preserve the spirit of a peacemaker, limiting violence to what is needed in resisting and deterring aggression, and extend­ing mercy to the vanquished and the captive.

Augustine’s insights guided much medieval thought. Aquinas applied both natural law and the principle of love to questions about the legitimacy of revolt against tyrannical government and about war, including military tactics like ambush. In the former case, since the use of force belongs only to lawful government, he argues that if a tyrant altogether violates the natural law on which governmental authority rests, it is legitimate only for those next in authority to use force against the tyrant and only to re­establish peace and justice for the common good.

The sixteenth-century Spanish theologian Francisco de Vitoria develops the theory further. Examining King Phil­ip’s wars against the American Indians, he condemns their lack of just cause. War, he insists, is not justified for religious reasons (to convert the heathen) nor for economic causes (to gain their gold) nor for political reasons (to extend the empire). The Indians, however pagan, immoral and uncivilized, are human beings with rights equal to those of all other persons. The natural law protects them against violence and injustice.

Vitoria also asks whether the soldier who doubts the justice of a cause should fight. Ordinarily, one should trust the lawful government to do what is lawful. But if justice is seriously in doubt, and if careful inquiry does not allay those doubts, then the soldier should refuse to fight. Selec­tive conscientious objection is the corollary of a just war ethic.

The Protestant Reformers meantime addressed the problem in similar terms. While Luther says little about natural law, he expounded on Aristotle’s concept of justice and ex­tended it from just actions to just intentions. The use of the sword, he argues, is divinely entrusted to governments in order to repel injustice and keep the peace. It can, there­fore, be a work of love for the common good. But only defen­sive war is just, including action to recover unjustly seized property from previous conflicts. This rules out religious wars, aggression and any attempt to revenge an insult. Only the highest governmental authority has the right to initiate military action, so that rebellion is always unjustified. It was on this basis that he opposed the famous Peasants’ Revolt. Yet the ruler, if wrong, should be disobeyed: selective con­scientious disobedience is not revolt.

John Locke’s famous Treatise on Civil Government bases the moral justification of defensive war on natural law, so that attacks on life or liberty may properly be repelled. Aggression is always unjust, and it gives the victor no rights at all over the conquered. Even in a just war, the just victor has power only over combatants, not over noncombatants (not even those who consented to aggression) and not over property. He may not impose a new government, for the citizens of a defeated state remain free and still have the right to form their own government.

Both in theory and in historical statement, then, the key thesis of the just war theory is that on the basis both of Scripture and of natural law, government (and only govern­ment) has the right to use armed force, and then only in the defense of peace and justice and with severe limitations on both the ends and the means adopted. Inasmuch as Chris­tians participate in government and serve as government’s official agents, then, they may—however regretfully and with however much moral caution—fight.


While the just war theory has played a major role in the thought and practice of the Roman Catholic Church and of Reformed, Lutheran and other Protestant groups, it faces serious problems.

First, the natural law ethic may tend to be overly optimis­tic both about man’s capacity to know what is right and to do what he knows. Theorists like Aquinas and Locke held that we can logically deduce an ethic from what we know of the nature of man so as to reach universal agreement about what justice is and what must characterize a just war. They thought the needed premises about man were both rationally accessible and certain, so that it remained only to draw our inferences regarding natural rights. This rationalistic opti­mism about the metaphysical basis of ethics has been shaken in the subsequent history of thought, and metaphysics now appears to be a much more modest undertaking. As a result, concepts of justice and their application to war tend to vary far more than past thinkers imagined possible. While the just war theory, therefore, is still alive and influential and while it can be supported by good reasons, its conclusions are not as readily accepted as they once were.

While it is true that the rule of law will neither cure nor wholly control a sin-ridden society, the fact remains that in God’s creation all individual and societal activities are and should be rule-governed. The role of civil law is to gov­ern activities within a society. The role of international law is to govern the activities of an international society. The just war theory provides a basis for laws of war – not because war is good but because it must be restricted and brought more and more under control, even while we work for its total abolition. In fact, just war ideals shaped the Geneva Convention and other international agreements, as well as helping to shape army regulations in the United States and elsewhere. Law is not enough, but it does have an educative function and, with the sanction’s of international opinion and pressure, it gains a deterrent function as well. At the Nuremberg trials it also exercised a punitive function in regard to war crimes.