The “war on terrorism” designates a fundamentally new framework for U.S. foreign policy. The new foreign policy framework is shaped by two countervailing political impulses. On the one hand, responding to terrorism is an act of self-defense. On the other hand, responding to terrorism requires military interventions and even overturning governments. These two impulses, toward self-defense and aggressive intervention, are countervailing, because while the right of states to self-defense is recognized by international law, interventions to overturn foreign governments transgress generally accepted limits on the legitimate use of military force. An on-going series of American military campaigns to “root out terrorism,” even though motivated by self-defense, might transform the United States into a global political tyrant, one attempting to impose its will on political realities it cannot fully understand and over which it has no genuine authority. Thus, striking an appropriate balance between the two countervailing impulses which shape the war on terrorism represents a central moral and political challenge for those who craft U.S. foreign policy.
 Christians can speak to the new set of challenges by drawing upon just war theory. Just war theory is often identified as a set of criteria used to assess the morality of a particular war. These criteria are subdivided into two categories, ius ad bellum, which concerns the political decision to resort to war, and ius in bello, which concerns proper conduct within war. All the just war criteria, however, are expressions of one underlying theory of politics.1 The criteria form a set of interrelated and interlocking guidelines which give shape to a Christian vision of statecraft, and which are intended to frame the way we think through the problems of international politics. In relation to the emerging U.S. foreign policy, three classic ius ad bellum criteria in particular; legitimate authority, just cause, and just intention; point in interrelated ways to the moral possibilities as well as the moral limitations of the war on terrorism.
Just War Theory and the Rules of International Politics
 Let us consider first the criterion of legitimate authority. This criterion constitutes the cornerstone of just war theory, because the right of a state to wage war is an extension of its right to use coercive power in the service of political goods, and only duly constituted political authority possesses this right. The use of coercive power in the service of political goods is necessary because of sin, which makes conflict a perennial feature of human community. Different interests within a political community assert competing claims, and left to their own devices they would vie with each other endlessly, leading either to continuous warfare or to anarchy. This conflict of power with power means that the common good of the political community must be preserved coercively, through the supremacy of power; that is, through the exercise of legitimate political authority. The right of political authority to use coercive power on behalf of the common good extends even to the point of killing. Thus, when the political community is threatened from abroad, a legitimate political authority may wage war to protect the common good with which it is entrusted.
 However, to understand the criterion of legitimate authority correctly, one must keep in mind that the right to use deadly force derives directly from responsibility for a discrete common good. Independently of that common good, independently of the intrinsic relationship between authority and a particular community, the right to wage war does not exist. Thus the criterion of legitimate authority both justifies and limits the right of states to wage war. A state may wage war to protect its common good, the good of the discrete community for which it is responsible, but it cannot wage war on behalf of political goods in general. Legitimate authority is limited authority, and if a state wages war to promote purposes unrelated to its common good, it ceases to act legitimately. This is true regardless of whether the state is pursuing an imperialistic or humanitarian purpose. A noble cause does not make authority legitimate.
 In other words, the criterion of legitimate authority implies judgments about the second ius ad bellum criterion, just cause. War must begin from a just cause, and a just cause is constituted by some harm to the discrete common good. For this reason just cause is sometimes restricted to self-defense. The right to self-defense derives from the state’s responsibility to preserve the political order in which discrete goods are embedded. The aggressor in war seeks to replace the existing political order, but the defender has a right to protect the threatened order. That is to say, the state has a right to self-defense, and violations of the international status quo constitute just cause for the recourse to war.
 But might just cause extend beyond self-defense? After all, the common good is comprised not only of order, but also of justice. Why should states not have the right to engage in aggressive military interventions for the sake of greater justice? The answer is that no individual state is responsible for justice in general. Legitimate political authority implies limited responsibility for the international political order. Aggressive interventions, even for good causes, represent illegitimate extensions of political authority over communities and political goods for which a state is not responsible.
 Thus, taken together, the criteria of legitimate authority and just cause seem to imply a particular vision of international politics. The vision is that of a self-regulating political order. Individual states tend to the good of their respective political communities and leave other states alone to do the same. This ensures, for the most part, a stable international political order. When one state over-asserts itself and attacks another, the defending state, or a coalition of states, will stop the aggressor and restore the status quo ante. Thus, international politics is self-regulating in a way domestic politics is not. Missing from the international political order is a supreme world authority, ordering the interests of the world’s many states.
 And yet, if we understand the ius ad bellum criteria this way, is not the implied vision of international politics inadequate? If within a single community unsupervised power leads either to war or anarchy, why would the same not be true of the international political community? Indeed, it would be true if the international political order were shaped by the dynamics of power alone. However, order in international politics is achieved not only through the balance of power, but also through the restraints placed on states by treaties and international law, as well as multinational and international organizations. That is to say, order in international politics results from the interaction of two distinct, but interlocking, ordering forces. The first is the order of power, which is the order achieved through the dynamics of power, the game of claim and counterclaim among competing states. The second is the order of law and morality, which is the order achieved through the pressure placed on states by international law and international organizations. The first of these, the order of power, is essential to international politics, while the second of these, the order of law and morality, is essential to a just international political order.2 The order of law and morality limits the freedom of action of states by establishing boundaries on the credible exercise of their power, thereby bringing justice to bear on the international political order without removing the exercise of power from international politics. In serving this critical function, the order of law and morality brings international states, and the order of power itself, into relation with the international common good.
 With this vision of international politics in mind, let us return to the question of aggressive military interventions. Consider the NATO intervention in Kosovo. In Kosovo, the NATO alliance of states initiated an aggressive military intervention against Yugoslavia, a sovereign state, in order to stop human rights violations inside the Yugoslavian border. NATO was, in effect, asserting a prerogative to protect the good of a political community over which it had no intrinsic authority. Since the NATO intervention appears to violate the criterion of legitimate authority, justifying it morally is difficult. However, one line of justification might proceed along the following lines: In intervening to stop human rights violations in Kosovo, the states of NATO were assuming responsibility for a more inclusive common good, the common good of Europe. Thus, the NATO intervention was a movement toward a more embracing form of political authority, even if a temporary one. This movement was made credible by the multinational character of the intervention, the necessity of securing a consensus of European states, and by the proximity of NATO to the European common good. Additionally, the constituted political authority in Yugoslavia, one would argue, had become illegitimate, so that in moving against the Yugoslav government the NATO powers were acting in a way analogous to “lower magistrates” in a justified revolution. Of course, in the case of an aggressive military intervention, the justified revolution is carried out not by “lower,” but by “higher” magistrates.
 I do not say this line of argument necessarily succeeds, only that a moral justification for the Kosovo intervention would most likely proceed along such lines. In any case, the movement toward more embracing political authority implied by the NATO intervention did not bypass the order of power, but rather depended on it. NATO acted as alliance of states, each wielding political power, which was collectively brought to bear on Yugoslavia. In the absence of that political power, political action in Yugoslavia would have been impossible. It was the order of power which came to bear against Yugoslavia, although the framework and vehicle for exercising that power was established by the order of law and morality, largely in the form of NATO. Through NATO the states of Europe were brought into relationship with the European common good.
 Therefore, at least theoretically, the ius ad bellum criteria allow for aggressive interventions on behalf of greater justice. Indeed, when viewed from a certain perspective, the ius ad bellum criteria even push outward toward more embracing forms of political authority. They push outward, however, only by bringing political authority into relation with more inclusive political goods. And bringing the exercise of power by political authority into relation with political goods is the function of the third ius ad bellum criteria, the criterion of just intention.
 War must be waged with a just intention. In its most general formulation, just intention means aiming to create a just peace. In the context of aggressive military interventions, however, aiming for a just peace means aiming for more inclusive political community. Aggressive interventions aim to change the currently existing political order; they aim to change the status quo. Thus such interventions, by their nature, cannot aim simply to restore order. They must aim to create a better order, one built on more comprehensive justice. More comprehensive justice, however, depends upon more comprehensive order, which, in turn, is a description of more comprehensive political community. Thus, the criterion of just intention increases the moral responsibility and broadens the political objectives of states engaged in aggressive military interventions.
 At the same time, the expanding scope of intention cannot continue indefinitely. The criterion of just intention, when taken to its outer limit, becomes nothing less than an expression of the proper exercise of power by a world government. But no coalition of states could claim to be the world government, unless they should replace the discrete common good of their respective political communities with the international common good as such. That, however, is impossible, because political authority itself derives from responsibility for a discrete common good. Genuine world government would be possible only if all the states of the world, in a kind of global social contract, alienated themselves from their legitimate authority and transferred it to the newly established world government. This global social contract, however-even setting aside its historical implausibility-is theoretically doomed, because the success of a social contract depends upon all parties being equal, and in international politics there is no equality of power. Thus any move toward world government would necessarily go through the existing order of power, and the newly constructed world government would become an instrument in the hands of more powerful states, who would be free to pursue their national interests under the banner of the international common good. Rather than a legitimate world-wide political authority, world government would more closely resemble a global political tyranny.3
 Yet political tyranny is the danger of every aggressive military intervention. Thus the criterion of just intention, while pushing out toward ever more inclusive forms of political community, on the one hand; pulls back from the simple extension of political authority in the name of greater good, on the other. Care of the international common good takes place through the interaction between the order of power and the order of law and morality. Power-wielding states pursue and protect their national interests, but their pursuit of national interest is restrained and brought into relation with the international common good through the order of law and morality. By regulating the conflict of power with power, the order of law and morality strives to achieve a coincidence between competing national interests and the international common good as a whole. In this way the international common good is fostered, but fostered indirectly.
Just War Theory and the War on Terrorism
 Just war theory, therefore, can be understood as attempting to provide a framework for ordering power in international politics in a manner that is conducive to the international common good. It is realist in its understanding of the dynamics of power, but internationalist in its moral implications. In this way, just war theory brings into focus the central moral problem of the war on terrorism. On the one hand, the war on terrorism implies a narrow definition of U.S. national interests, limited to self-defense and domestic security. On the other hand, the war on terrorism implies an expansive definition of U.S. global objectives, extending all the way to regime change and reshaping the international political order. Consequently, insofar as policy makers view global terrorism as a matter of self-defense (focusing thereby on political considerations indicated by the criteria of just cause and legitimate authority), they will be inclined to approach the war on terrorism unilaterally. However, insofar as policy makers view global terrorism as a matter of the international political order (focusing thereby on political considerations indicated by the criteria of just intention and legitimate authority), they will be inclined to approach the war on terrorism through international frameworks.
 The truth is that the war on terrorism is both a matter of self-defense and of international politics, and the moral and political challenge for U.S. political leadership is to craft a foreign policy that protects Americans from global terrorism while also respecting international law and avoiding ambitious military crusades that transgress legitimate political limits. Bringing a just war perspective to bear on U.S. foreign policy after September 11 means calling attention the fact that the war on terrorism cannot be formulated simply in terms of self-defense and American national interests. American interests are at stake, but those interests must be brought into relationship with the international common good.
 International arrangements in which the United States assumes a prominent role in shaping and reshaping coalitions of power to battle terrorism, but is simultaneously restrained by those coalitions, would seem compatible with the just war framework. Something like this has been happening in Afghanistan. There, the United States has been the dominant and organizing power in a coalition of powers seeking the destruction of the al-Qaida network. The multinational character of that intervention goes a good way toward setting to rest concerns about legitimate authority. Conversely, had the United States acted in Afghanistan unilaterally, the intervention would have raised questions of legitimacy, even though the United States was acting in self-defense. Destroying al-Qaida required toppling the Taliban regime. Regime change, however, moves beyond self-defense to refashioning the international political order, and refashioning the political order must be done within the framework of international law and institutions.
 The interlocking relationship between national and international interests should also be kept in mind when developing a strategy for moving the war on terrorism beyond Afghanistan. When considering aggressive interventions political leaders should pay attention to the political factors indicated by the criteria of just intention and legitimate authority. A just intention requires considering the reasonable probability of success, and success must be measured not only militarily, but politically. Thus assessing the probability of success requires attending to the limits implied by the criterion of legitimate authority. When brought to bear on the question of aggressive military interventions, the criterion of legitimate authority militates against unilateralism. Unilateral interventions entail greater risk of sliding into political domination, while multilateral interventions, because they must attend to regional political realities, enjoy greater probability of producing a just peace. In Afghanistan, the United States has needed to work with political actors in the region in order to fashion a new regime in a way that accords with just intention, and has thereby found itself engaged in the work of “nation-building.” Indeed, “nation-building” is morally concomitant with aggressive military interventions.
 Of course, none of these considerations establish absolute limits by which to assess the legitimacy of particular military interventions. However, the purpose of just war theory is not to provide churches and their theologians with a checklist for saying “yes” or “no” to particular wars. Rather just war theory is a framework for political prudence, a guide for moral reflection on the political use of deadly force. Accordingly, the task for Christian ethics is to use the just war framework to pose questions about the means with which, and the purposes to which, military power is being placed. By asking such questions, Christian ethicists may help to frame public discussion on questions of foreign policy, even if they cannot provide definitive answers to their questions. Answering such questions is, necessarily, the responsibility of political leaders. But if just war theory can shape public debate, it may also shape the conceptual framework within which political leaders make decisions about the recourse to force.4
Helmut David Baer is an Associate Professor of Theology and Philosophy at Texas Lutheran University.
1. Cf. the suggestions of Paul Ramsey, “The Uses of Power” in The Just War: Force and Political Responsibility (New York: Charles Scribner & Sons, 1968). 3-18; also Theodore R. Weber, “Vengeance Denied, Politics Affirmed: The Reconciling Criterion of Just Intention,” Societas Ethica (Jahresbericht/Annual 2000), 170-176.
2. The distinction I am making draws upon Paul Ramsey: “The use of power, and possibly force, is of the esse of politics. By this I mean it belongs to the very act of being politics. You never have politics without the use of power, possibly armed force. At the same time the use of power, and possibly the use of force, is inseparable from the bene esse of politics. By this I mean that it is inseparable from politics’ proper act of being politics, inseparable from the well-being of politics, inseparable from the human pursuit of the national or the international common good by political means. You never have good politics without the use of power, possibly armed force.” Ramsey, “The Uses of Power,” 5.
3. My analysis of the problem of world government draws upon Paul Ramsey, “Pacem in terries,” in The Just War, 70-90; Reinhold Niebuhr, The Children of Light and the Children of Darkness: A Vindication of Democracy and Its Traditional Defense (New York: Charles Scribner & Sons, 1944), 153-190; and Reinhold Niebuhr, “The Illusion of World Government,” in Christian Realism and Political Problems: Essays on Political, Social, Ethical and Theological Themes (New York: Charles Scribner’s Sons, 1953), 15-31.
4. Cf. Paul Ramsey, “The Ethics of Intervention,” in The Just War, 19-41.