Americans have a hard time talking sensibly to one another about the war in Iraq in part because we lack the necessary vocabulary. What do I call someone who is a liberal Democrat, a lifelong opponent of imperialism, deeply mistrustful of the Bush administration and its corporate connections, yet who supported the invasion of Iraq to topple Saddam because it would end the suffering of Iraqis? To call such a person "pro-war" feels false. But what's the correct term?

One of the gifts my wife got me for the holidays this year was "Semi-Detached Idealists: The British Peace Movement and International Relations, 1854-1945," by Martin Ceadel.

The book was more than 30 years in the making. In it, I find a frame of reference for attitudes toward the Iraq war. That is, in describing the peace movement in a different time and place, Ceadel uses a vocabulary that can be applied to the current situation -- excluding outright traitors, profiteers, or people whose primary motivation in this is something other than the question of justice and war.

He describes two types of peace advocates, and three brands of people opposed to them. In the extreme wing are the militarists, who "glorify conquest on the grounds that it advances civilization."

What Ceadel calls (and, being British, spells) the defencists "hold that the incidence of war is minimized when all countries reject aggression and maintain national defences strong enough to deter others from attempting it." This is the si vis pacem, para bellum view, which probably has been the popular view among politicians and citizens in Britain and the U.S. over the long run for the past 200 years.

Between these two are the crusaders, who "believe that the first use of military force is sometimes necessary to achieve justice and thereby create the conditions for lasting peace."

It's pretty clear which of these three classifications accurately describes the "neo-cons," and the other architects and supporters of the current U.S. effort in Iraq.

Crusading is an awkward word for this idea, because it conjures up specific images of the Christian Crusades of the Middle Ages. Those mass movements can be understood on several levels, many of which have nothing to do with the modern concept being described. Worse, "crusader" has particular unpleasant associations for non-Christians.

Yet it is felt as the right word by Ceadel and other specialists on this topic, and it probably was felt as such by President Bush when he used it as his administration began to change its foreign policies after 9/11. He was mocked for that, but in fact it is just the word many academic political scientists use among themselves. Bush and Bin Laden both at different times have called America's work in Iraq a "crusade." However darkly and differently, both are right.

Crusading is nothing new; it was expounded in the 1790s both by the liberal Tom Paine (who wanted Revolutionary France to conquer Britain and reform it) and the conservative Edmund Burke (who wanted Britain to conquer Revolutionary France and eradicate its bloody and dangerous regime). Throughout the 19th century, it took the lead from time to time in the British popular mind, usually expressed as a yearning to aid revolutionaries and freedom fighters against repressive empires. Lord Byron was crusading when he went to help the Greeks against the Ottomans. The crusading spirit ran high again when the Hungarians (1840s) and the Italians (1850s) rose against the Austrians, and the Bulgarians (1870s) rebelled against the Turks.

Ceadel's topic is Britain, but he looks beyond it for comparisons. In his opening chapter, he outlines a rough prediction model to discover what is likely to be the dominant view of war and peace in a nation, based on its relative security and on the liberality of its institutions. Germany, with high insecurity, feudal structure, and historically illiberal religions, tended toward militarism. America is at the opposite pole, Ceadel writes, and crusading is one of its natural states.

The United States, however, was too secure and too liberal for the goal of the peace movement: its geo-strategic security was so great as to allow it to ignore the balance of power; and its model liberal constitution and puritan tradition, unchecked by a feudal elite, also contributed to a self-righteous approach to the international system which oscillated between the desire to take charge of it and the desire to wash its hands of it. American peace sentiment thus leaked away into crusading in moments of confidence and into isolationism in moments of disappointment. [p.22]

The peace movement adherents also come in more than one flavor, and their agendas sometimes clash.

There is a group, at times a majority, that "argues that the abolition of war will be achieved only by improving the structure either of the international system or of its constituent states and that until this has been achieved defensive military force may be needed to protect these reforms." To label them, Ceadel turns to A.J.P. Taylor's awkward term pacificist. It's only one short syllable removed from "pacifist," and the eye is at risk of reading the longer word as the shorter one, a problem Ceadel acknowledges by always printing pacificist in italics.

Whatever you call it, this group, while more practical than absolute pacifists, easily can get tangled in contradictions. Reading about it, I thought of the Quaker pacifists in the North who urged Lincoln to wade through gore to crush the Southern rebellion. Ceadel points to the way out of this ethical briar patch:

Only when pacificists have managed to link their support for war to the promotion of an evidently eirenic reform, such as the creation of a league of nations, have they been able to make their predicament as pro-war members of the peace movement seem less paradoxical.

For centuries, in the Western Christian mind, war was an evil but unavoidable fact of life in a fallen world. Peace movements in Britain began to take shape only gradually, after the 1730s. They were children of the British Enlightenment, with its remarkable marriage of evangelical Christian values and rational humanist ones.

The idea that war could -- and should -- be banished from human experience began to express itself politically in the 1790s, Ceadel writes, when Britain fought France. Interestingly, then, the first real pacifist movement arose when Britain went to war with Robespierre's tyranny, one of the worst in modern European history, which slaughtered its citizens and threatened its neighbors and gave the world's languages the fresh-minted word "terrorism."

The argument between crusaders and pacificists seems to describe the relationship between Europe and America in the early 21st century. They share a vision, and they squabble over how to get there.

Before there can really be such a strong, solid legal framework for international relations, the world has to change. Most of the world will have to learn such concepts as the rule of law, life under incorruptible administrations, and independent judiciaries. These things may be in place in Western Europe, but they are unknown in the nations where the majority of human beings live.

I might add also that these things were achieved in Europe because brave people there took up guns, risked their lives, and drove out tyrants and demagogues, sometimes with some help from Americans. I also might point out that any court -- whether global or local -- is useless without some sort of force to back up its decisions.

Even in semi-developed places like Mexico and China, incorruptible, independent judicial systems are not part of daily life. Even in the U.S., their hold is not as sure as it ought to be.

To achieve the kind of world we wish to live in, wars like the Iraq invasion will have to happen first. In the U.S.neo-con/neo-imperialist ethos, the Iraq war is meant to spread this value system of law, freedom, justice, and prosperity into one of the darkest regions of the world. There can't be real global justice if a huge chunk of the planet lives under the kind of dictatorship that turned the Garden of Eden into a charnel house, where thousands of weeping people are now digging up the skulls of their loved ones.

The present system of world justice grew out of Nuremberg, and in a larger sense it grew out of World War II, at a time when the greatest threat to human life and dignity was war between nations. So its structures are designed to prevent wars. But they do nothing about what goes on within any nation. A country like Zimbabwe or Burma can go about butchering and raping its citizens yet be judged "peaceful" under international law.

Those who protested the Iraq war worry that the alternative to international law is terror, cowboy-ism, the law of the jungle. The people of Iraq were already living under the rule of terror, thugs, and predators. International law was what would have been invoked to prevent American and British troops from putting an end to that nightmare.

Can you spread love of peace and respect for law from the barrel of a gun? Of course not. But in failed nations you have to clear out the rottenness and the deadwood, and protect the open land, for the years it will take for these things to grow and grow strong there. The British conquered India with brutality and bloodshed on a vast scale. They exploited the resources (and made massive investments in the infrastructure of the colony in doing so) and neglected the people, largely. But by the time they were pushed out, by a British-educated subject, they left an India prepared to become the world's largest democracy, with a tradition of the rule of law, a sense of national identity, and widespread education.

Yet we will be told we are "imposing Western values" when we attempt to do this in Iraq. I do not think that is so. In an important address in February, Bush made it very clear that "the world has a clear interest in the spread of democratic values," not least because "free nations do not breed the ideologies of murder." These are humanity's values, not America's.

By contrast, recently I read a quote by Finnish Prime Minister Paavo Lipponen, who said in London last year that "the EU must not develop into a military superpower but must become a great power that will not take up arms at any occasion in order to defend its own interests." After 4,000 years of living by the sword, the continent that came to rule the world through force of arms has in one generation entirely given it up.

The American covenant called on us to help show the way for the liberation of man. And that is today our goal. Thus, if as a nation there is much outside our control, as a people no stranger is outside our hope.

Meanwhile, across the Atlantic:

Change has brought new meaning to that old mission. We can never again stand aside, prideful in isolation. Terrific dangers and troubles that we once called "foreign" now constantly live among us. If American lives must end, and American treasure be spilled, in countries we barely know, that is the price that change has demanded of conviction and of our enduring covenant.

But it is the only spirit that also, coherently, can say:

In a land of great wealth, families must not live in hopeless poverty. In a land rich in harvest, children just must not go hungry. In a land of healing miracles, neighbors must not suffer and die unattended. In a great land of learning and scholars, young people must be taught to read and write.

For the more than 30 years that I have served this Nation, I have believed that this injustice to our people, this waste of our resources, was our real enemy. For 30 years or more, with the resources I have had, I have vigilantly fought against it. I have learned, and I know, that it will not surrender easily.

But change has given us new weapons. Before this generation of Americans is finished, this enemy will not only retreat--it will be conquered.

Justice requires us to remember that when any citizen denies his fellow, saying, "His color is not mine," or "His beliefs are strange and different," in that moment he betrays America, though his forebears created this Nation.