During the months that I spent writing these lectures, the Soviet Union was breaking up, the wars of the former Yugoslavia had begun, and the satellite states of East Europe were enjoying a very new independence. So it was natural and easy for me to take the arguments for self-determination as a key example of moral minimalism (see chapter four). The daily newspapers and the television news provided the best possible description of how moral argument works, or doesn''t work, "abroad"--when men and women have to talk in ways that people they don''t know will understand. But if we take in a broader swath of history, it is the rules of war that best exemplify minimal morality. For here the people who must understand the rules are not only living on different sides of political and cultural boundaries, they are also actively engaged in fighting each other across those boundaries. And yet, whether they live by the rules or break them, there is no question that they know what the rules are. The very lies they tell testify to their knowledge. The rules can be understood because they are based on the right to life and to self-defense, minimal ideas indeed, though readily disputed when they are collectivized.

How do we identify the collective subject of the right of self-defense? Did the old empires have a right to defend themselves against national liberation movements? Or does the right belong only to sovereign states defending their national territory? And what about brutally oppressive states at war with their own citizens--what kind of rights can they have? These are hard questions, but even when they are answered differently, the answers come in a language that is culturally non-specific, translatable across all boundaries. Arguments about self-defense are fairly readily understood; arguments about the defense of others are harder--as we have seen in recent years when humanitarian intervention is called for or criticized. But what is at issue in those arguments is not the value of stopping a massacre, but the costs of doing so, the likelihood of military success, and the prospect of a non-murderous aftermath. No one (or virtually no one) will attempt to defend the massacre. The same thing is true of the arguments for "non-combatant immunity," which derive from the universal right to life. Soldiers at war forfeit that right, but the civilians they leave behind possess it to the full. Targeting them is widely recognized to be murder. And the same recognition gives us the rule--however often it is violated in practice--that when soldiers aim at military targets, they must make every effort to avoid or minimize injury to innocent bystanders.

Of course, we will disagree about the precise meaning of "non-combatant" and about the reach of "every effort." But these arguments have, so to speak, a universal shape, and when they go on at the United Nations, in international courts, or in the global media, no-one can claim in good faith that they are imperial impositions or comprehensible only, let''s say, in the West. Everyone understands who wants to understand. I don''t mean to say that the minimal morality of war regularly carries the day. It obviously doesn''t: armies collectively and soldiers individually often act in radical disregard of the rules, brutally, even murderously. But when they defend what they have done, they don''t deny the rules, they deny the disregard; they deny the murders. We know what war crimes are, even when we disagree about whether they were committed in this or that case, or by whom they were committed. The rules of war may have been created over the course of many wars, through a kind of negotiation.

I imagine that the convention that protects prisoners of war, for example, originated in a series of offers, sometimes accepted, sometimes not: we won''t kill the soldiers we capture if you don''t kill the soldiers you capture. At some point, perhaps after many failed experiments, the convention was agreed upon and codified. And only then was it incorporated into the thick morality of each party. Thin comes before thick. Maybe. But, as I argue in the preceding chapters, it seems more likely that the agreement about prisoners was made possible in the first place by the recognition in each thick morality that non-threatening human beings should not be killed. It just takes a long time to make sure that this recognition is actually shared. People draw upon the resources of their own culture when they respond to people from another culture--and they look, not foolishly, for a similar response from the other side.

The idea that war is a combat between combatants from which non-combatants should always be shielded appears in every religion and in every high civilization. It is everywhere rooted in a larger set of moral understandings and expressed in a particular moral language, but the principle is pretty much the same across the board. Think about all the historical iterations of this simple idea about combatants and non-combatants: it has been expressed in the language of Confucian ethics, in the Hindu classics, in ancient Jewish texts, in Sharia law, and in Catholic natural law; and it has been defended with utilitarian arguments, with Kantian deontological arguments, and, most recently, by reference to human rights. My impulse, when I was writing Just and Unjust Wars, was to say: it really doesn''t matter where you get it from, so long as you get it right. But of course it does matter to the men and women trying to get it right. And the idea will be developed differently in different times and places. The most fully developed version of the idea was the work of Catholic theologians in the medieval and early modern periods, and what they produced became the basis of both religious and secular doctrines of "just war." Though Catholic just war theory was indeed the work of theologians, it wasn''t described as the word of God.

It was, instead, a reading of natural law, accessible to all rational beings, believers and infidels alike--and obligatory for all of them. So the best Catholic theologians insisted upon the right of heathen nations to defend themselves even against crusading Catholics. Just war was a universal idea; holy war was not. (excerpted from the afterword of the new edition).