History does not arrange itself for our benefit. The labors of every historian who ever lived have barely scratched its surface. It does not repeat itself, form itself into convenient cycles, offer cautions for the foolish, or humility for the arrogant.

If it did any of these things, humankind long ago would have achieved a state of perfection, guided by our cumulative historical wisdom. As we learned once more and to our everlasting regret on September n, we are far, far from wise.

The ruins of the tragedies were still smoldering as the world began wondering how to make sense of them. As if sense could banish grief, we looked toward the past to help us explain what we felt. The surprise and shock of Pearl Harbor were immediately available, but as New York City’s casualties rose well above 1941∗5, even that disaster seemed less compelling. As investigations began to point toward Afghanistan, public commentary fixed first on the nineteenth century’s imperial misadventures, then on more recent wars. The Soviet Union’s ill-fated war seemed to hold important clues: the Soviets’ own Vietnam, the rise of the mujahedeen, the rise of radical Islamism (not, we are reminded by the experts, true Islam). Here we can find some of our enemies in their youth, learning their trade and sharpening their hatreds.

As we turn the pages faster and faster, our historical knowledge turns back on itself, overwhelming our intellect, forcing us to retreat to our senses. Now we are in the presence of a different sort of history, history unprocessed, undigested history, history in the raw. This is the kind of history that moves one not only to know but to act. This is the history that we are making now.

The austere doctrines of scholarly history do not acknowledge its curative powers; the search for historical understanding can be as important as the knowing, and revisiting friends centuries old can help you see history in new and different ways. These are not the applications of history. They are the applications of the historian in all of us.

Lately, I have kept Thucydides’ History of the Peloponnesian War a bit closer to hand. This ancient book speaks to me more usefully than many others; at times, I think it is a strangely modern book, a story of how an empire was torn apart by the stresses of war. Thucydides is often reviled as a pessimist, as unfeeling in the face of tragedy. I have come to see his story as a Greek tragedy, and like any tragedy, it is not a prediction but a cautionary tale. He believed his history was worth knowing and that it would be known. “My work is not a piece