The just war tradition came into being during the Middle Ages as a way of thinking about the right use of force in the context of responsible government of the political community. With deep roots in both ancient Israel and classical Greek and Roman political thought and practice, the origins of a specifically Christian just war concept first appeared in the thought of Augustine. A systematic just war theory came only some time later, beginning with Gratian's Decretum in the middle of the twelfth century, maturing through the work of two generations of successors, the Decretists and the Decretalists, and taking theological form in the work of Thomas Aquinas and others in the latter part of the thirteenth century. Later in the Middle Ages, and particularly during the era of the Hundred Years War, this canonical and theological conception of just war was further elaborated by incorporation of ideas, customs, and practices from the chivalric code and the experience of war, from renewed attention to Roman law, especially the jus gentium, and from the developing experience of government.
All this took place within a maturing theory of politics first outlined by Augustine in City of God, which conceived the good society as one characterized by a just order and thus one at peace both within itself and with other polities similarly justly ordered. Within this conception of politics the ruler's right to rule is defined by his responsibility to secure and protect the order and justice, and thus the peace, of his own political community and also to contribute to orderly, just, and peaceful interactions with other such communities.
The place of the justified resort to force within this overall conception was, for medieval and early modern thinkers alike, encapsulated in a verse from the Apostle Paul, Romans 13:4: "For [the ruler] is God's minister to you for good. But if you do evil, be afraid; for he does not bear the sword in vain. He is God's minister, an avenger to execute wrath on him that does evil." The use of armed force in this conception was thus both strictly justified and strictly limited: it might be undertaken only on public authority and for the public good. As Aquinas summed it up in the Summa Theologica, for a resort to the sword to be justified it must be on the authority of a sovereign, for a just cause rightly defined, and for a right intention, which included both avoidance of evil intentions and the positive aim of securing peace--peace understood, after Augustine, as tranquilliras ordinis, the tranquillity of a just political order. Elsewhere in the developing tradition limits were set on how such justified force might be used: certain classes of persons were normally to be treated as noncombatants and not to be harmed directly and intentionally in their persons or property, and lists were made of weapons not to be used because of their indiscriminate or especially deadly effect.
This was the tradition of just war in its classic form. Taking explicit shape in Christian theology and canon law, it was also a Christian tradition in a broader sense--the collected consensus of the Christian culture of the West on the justified use of force, set squarely within a normative consensus on the purpose of political order. This conception of just war was passed to the early modern age and known and used by such theorists as the Neoscholastics Vitoria, Soto, Molina, and Suarez, by the Protestant Reformer Martin Luther, the Puritan theologian William Ames, the theologically trained jurist Hugo Grotius, and others at the dawn of the modern era. For all of them it constituted the consensual normative wisdom.
Because of the cultural changes of modernity, however, the just war tradition has been carried, developed, and applied not as a single cultural consensus but as distinct streams in Catholic canon law and theology, Protestant religious thought, secular philosophy, international law, military theory and practice, and the experience of statecraft. Thus we find examples of the just war tradition in theorists of the law of nations and in positive international law; we have a form of this tradition in modern military codes, rules of engagement, and praxis; and two of the most important theorists of just war over the past forty years have been the Protestant theologian Paul Ramsey and the political philosopher Michael Walzer. All these streams of thought have also produced other normative conceptions of the political community, of the roots and responsibilities of government, and of the relations among such communities. In the modern context the just war teachings of the Catholic Church lie alongside the contributions of these other spheres to the developing tradition.
Yet it is one of the great losses of just war thinking--and of modern societies--that from the middle of the seventeenth century through the middle of the +twentieth, creative religious efforts to think through the meaning and implications of this tradition have ranged from occasional to notably lacking. In Catholic thought the idea of just "war remained as an element in canon law and moral theology, but largely without substantive development, almost as a historical artifact. Perhaps more important in the larger picture, the concept of just war became increasingly disconnected from ongoing developments in Catholic thinking about the proper purpose of political order and the proper institutions to embody that purpose. The Catholic theory of international relations, which had originally been framed in terms of the Augustinian understanding of political order, justice, and peace within and among political communities, became increasingly tied to developments in secular international law, as we see in such works as John Eppstein's The Catholic Tradition of the Law of Nations, published in 1935. Meanwhile, Protestant thought, influenced by the moral idealism and historical optimism of the eighteenth and nineteenth centuries, followed a similar course but moved closer and closer to a form of utopian pacifism in which war would be eliminated because of the increasing perfection of human social institutions.
The past forty years have brought a recovery of the idea of just war in Christian ethical discourse, and this has invigorated a larger engagement with the just war idea in policy debate, in the military sphere, in philosophical thought, and in dialogue between moral reflection and international law. As a result of these developments, just war debate is more robust and widespread than in any period since the mid-sixteenth to mid-seventeenth century, the age of Vitoria and Suarez and Grotius. But important elements of the connection with the earlier tradition, the idea of just war in its classic form, have been lost in much of this debate, including in recent Catholic thought. On the one hand, confusion has emerged between the Church's commitment to its teaching on just war and what has come to be called "the Catholic peace tradition," a tradition of avoidance or renunciation of participation in armed force historically associated with the religious life but, since the Second Vatican Council, made over into a case for pacifism for Catholic laity as well. On the other hand, a line of interpretation has developed that has been influenced by the secular philosophical concept of prima facie duties, by prudential (and contingent) judgments about the inherent immorality of contemporary war, and by well-intentioned but rather utopian investment in the United Nations system.
I will return to these themes below, but for now my point is a simple one: Catholic moral theology needs to reestablish a connection with the broader and deeper just war tradition, and especially with the form given that tradition in the classic period of its development. This is both important and necessary, in my view, for three fundamental reasons. First and most basic is the substantive reason: looking to the tradition in its classic form will bring Catholic thought on just war back into engagement with the conception of the use of force as a tool to be employed in the proper exercise of government to combat evil and other forms of injustice in the service of the public goods of justice, order, and peace.
Second, robust reflective engagement with the tradition of the Church is an essential element of the Catholic way to theological and moral clarity. Other elements are, of course, important as well: engagement with Scripture, philosophical reasoning, and reflection on empirical evidence. Protestant ethical reflection does all these as well, in different ways and with different emphases. But Catholic moral thought is distinctive because it holds that wisdom resides in the record of the Holy Spirit's interactions with the faithful through the history of the Church. For this reason one cannot be truly Catholic without respecting and seeking to understand the record of the tradition, and one cannot have a genuinely Catholic contemporary understanding of just war without a grasp of the Church's normative tradition on just war and its place in the theory of statecraft and international order.
Third, it is important for the broader contemporary just war debate for Catholic moral and political thought to reconnect with this normative tradition and to use that connection to advance and enrich that debate. Such enrichment is sorely needed. The conception of sovereignty as moral responsibility in the classic just war tradition contrasts importantly with the morally sterile concept of sovereignty in the Westphalian system. (Three centuries of experience with international relations stemming from the 1648 Peace of Westphalia have demonstrated that the principles of national sovereignty, territorial integrity, and noninterference in domestic affairs can, if interpreted in strictly procedural terms, conduce to protect tyrants while they oppress, rob, torture, and kill the citizens of their...