Robert D. Richardson is an award-winning biographer whose books include Henry Thoreau: A Life of the Mind , Emerson: The Mind on Fire , and William James: In the Maelstrom of American Modernism. He edited The Heart of William James , being published this week by Harvard University Press.

William James, the greatest American philosopher and a founding figure of both modern psychology and modern religious studies, died 100 years ago last week. It is also just a century since the publication of James’ landmark manifesto, “The Moral Equivalent of War,” one of the last things published before his death. James was anti-imperialist, and he opposed, as did a few other Americans, the Spanish-American war, especially its extension to the Philippines.

By 1910, James was against war itself. His notion of a “war against war,” as he puts it, had been building for at least a decade. His position, unusual still today among peace advocates, recognizes that war is a deeply attractive thing for many of us, and that we do not in fact want peace—at least not entirely. He wrote before D.H. Lawrence observed that “the essential American is hard, isolate, stoic, and a killer.” And long before Simone Weil’s “The Iliad, or, the Poem of Force,” James noted that “the Iliad is one long recital of how Diomedes, and Ajax, Sarpedon and Hector killed.” It is the greatest strength of James’ argument that he seriously recognizes the grip war has on us and will continue to have. Rather than say we all love peace, let’s not fight, James instead tries to harness the war-spirit and turn it against itself. We will have to kill war.

James made two concrete proposals for how this might be done. In The Varieties of Religious Experience (1902), he reached back to Thoreau’s Walden and the idea, discussed in the first chapter of that classic, of voluntary poverty. (When Americans see that phrase, they see “poverty” written in boldface. We must train ourselves to see “voluntary,” meaning willed, written in caps and printed in red.)

“What we now need to discover in the social realm is the moral equivalent of war,” James wrote in Varieties, “something heroic that will speak to men as universally as war does, and yet will be as compatible with their spiritual selves as war has proved itself to be incompatible. . . . May not voluntarily accepted poverty be ‘the strenuous life’ without the need of crushing weaker peoples?”

By the time he wrote “The Moral Equivalent of War,” James had dropped the idea of voluntary poverty or simplicity—the sort of thing advocated in Walden, and by Wendell Berry, and by the modern “freegans”—in favor of something very close to the modern idea of the Peace Corps. “To coal and iron mines, to freight trains, to fishing fleets in December, to dish-washing, clothes-washing, and window-washing, to road building and tunnel making, to foundries and stoke holes, and to the frames of skyscrapers, would our gilded youth be drafted off, according to their choice, to get the childishness knocked out of them, and to come back into society with healthier sympathies and soberer ideas.”

It was not an accident that when the Civilian Conservation Corps built a leadership camp in Sharon Vermont in 1940, it was called Camp William James. But many Americans still have an unshakable belief that violence is the only real way to settle disputes and is fundamental to manhood. James himself noted that the only tax we pay willingly is the war tax.

The war against war has not been going very well lately, but we must take what solace we can in the fact that the struggle continues. We have had the war on poverty, the war on drugs, and many other such initiatives, and the idea that there might really be a moral equivalent of war refuses to die. If and when war itself is finally vanquished, it will be in the way James first showed. And as much as we need a concrete proposal, a workable mechanism, a specific way, we also need the resolve to carry it through. And here, just as the peace movement needs to learn from its enemy, war, how to fight back, we can learn from our former enemies something about resolve. It was an article of faith among old communist organizers that there was never more than 10% of the people who were true, committed revolutionaries, and never more than 10% who were unalterably opposed. The great struggle, then, is to get the overwhelming 80% in the uncommitted middle over to your side.

The war against war has not been won, but neither has it been irretrievably lost. We owe to William James the very idea that there might even be such a thing as a moral equivalent to—and not just a moral argument against—war.