I SOME political theories die and go to heaven; some, I hope, die and go to hell. But some have a long life in this world, a history most often of service to the powers-that-be, but also, sometimes, an oppositionist history. The theory of just war began in the service of the powers. At least that is how I interpret Augustine’s achievement : he replaced the radical refusal of Christian pacifists with the active ministry of the Christian soldier. Now pious Christians could fight on behalf of the worldly city, for the sake of imperial peace (in this case, literally, pax Romana); but they had to fight justly, only for the sake of peace, and always, Augustine insisted, with a downcast demeanor, without anger or lust.1 Seen from the perspective of primitive Christianity, this account of just war was simply an excuse, a way of making war morally and religiously possible. And that was indeed the function of the theory. But its defenders would have said, and I am inclined to agree, that it made war possible in a world where war was, sometimes, necessary. From the beginning, the theory had a critical edge: soldiers (or, at least, their officers) were supposed to refuse to fight in wars of conquest and to oppose or abstain from the standard military practices of rape and pillage after the battle was won. But just war was a worldly theory, in every sense of that term, and it continued to serve worldly interests against Christian radicalism. It is important to note, though, that Christian radicalism had more than one SOCIAL RESEARCH, Vol. 69, No. 4 (Winter 2002) The Triumph of Just War Theory (and the Dangers of Success) BY MICHAEL WALZER version: it could be expressed in a pacifist rejection of war, but it could also be expressed in war itself, in the religiously driven crusade . Augustine opposed the first of these; the medieval scholastics , following in Aquinas’s footsteps, set themselves against the second. The classic statement is Vitoria’s: “Difference of religion cannot be a cause of just war.” For centuries, from the time of the Crusades to the religious wars of the Reformation years, many of the priests and preachers of Christian Europe, many lords and barons (and even a few kings), had been committed to the legitimacy of using military force against unbelievers: they had their own version of jihad. Vitoria claimed, by contrast, that “the sole and only just cause for waging war is when harm has been inflicted.”2 Just war was an argument of the religious center against pacifists, on the one side, and holy warriors, on the other, and because of its enemies (and even though its proponents were theologians), it took shape as a secular theory—which is simply another way of describing its worldliness. So the rulers of this world embraced the theory, and did not fight a single war without describing it, or hiring intellectuals to describe it, as a war for peace and justice. Most often, of course, this description was hypocritical: the tribute that vice pays to virtue. But the need to pay the tribute opens those who pay it to the criticism of the virtuous—that is, of the brave and virtuous, of whom there have been only a few (but one could also say: at least a few). I will cite one heroic moment, from the history of the academic world: sometime around 1520, the faculty of the University of Salamanca met in solemn assembly and voted that the Spanish conquest of Central America was a violation of natural law and an unjust war.3 I have not been able to learn anything about the subsequent fate of the good professors. Certainly, there were not many moments like that one, but what happened at Salamanca suggests that just war never lost its critical edge. The theory provided worldly reasons for going to war, but the reasons were limited —and they had to be worldly. Converting the Aztecs to 926 SOCIAL RESEARCH Christianity was not a just cause; nor was seizing the gold of the Americas or enslaving its inhabitants. Writers like Grotius and Pufendorf incorporated just...