There is always the danger, in a country of three hundred million people, that we will overgeneralize from the extreme example only to find, in retrospect, that the extreme remained merely the extreme. The bad verdict in the O. J. Simpson trial did not make for an open season on ex-wives, nor must the apparent injustice in the case of George Zimmerman, acquitted after shooting Trayvon Martin dead, make for one on African-American teen-agers in hoodies.

But at least some of the factors driving the verdict—in particular, the Stand Your Ground law in Florida—don’t seem extreme at all, in the sense of alien to the American scene. (That the shooting happened in Florida, though, does seem to provide mordant further proof of my intuition that Florida is now where the theatre of American violence plays out, as it once did in Los Angeles.) One can start by pointing to a connection between two weird pieces of the whole horrible business. First, why would anyone, as Zimmerman did, forge such an urgent sense of identity from his role as an armed, make-believe policeman or neighborhood vigilante—an identity that led him, at a minimum, to walk around with a concealed handgun and take needless risks likely to end in tragedy?

Second, and just as important: Why does Florida allow men to carry guns so casually? How could Stand Your Ground, which seems, after all, like an invitation to the kind of violence that laws and societies are meant to prevent, have evolved with such seeming nonchalance?

As it happens, about twenty years ago I did a series of lectures, at the New York Public Library, on the romance of violence in American life. I had come upon a body of nineteenth-century common-law practice that helped explain the evolution of Americans’ love of violence—and, surprisingly, revealed something about Abraham Lincoln’s view of it. It began with a study of duelling in America: duelling had largely died out in Europe by the middle of the eighteenth century, but it was revived, in a self-consciously romantic manner, in the seventeen-eighties. From there, it spread to England, and then America.

In France and England, though, duelling was meant to reinstate an aristocratic code of honor against the encroachment of the middle class. (This is dramatized in the strange and wonderful Ridley Scott film “The Duellists.”) But in the ideal European duel it was likely that both parties would survive. In America, around the same time, the code of honor took a very different form. American duels were dangerous, usually fought to the death, and they left in their wake that special American thing the feud. Instead of dissolving personal quarrels in a solvent of honor, the American way of duelling intensified them. In 1808, for instance, two men fought a duel in Maryland—with rifles, and at thirty steps. During the Jackson Administration, when General Armistead Thomson Mason challenged Colonel John Mason McCarty, McCarty, it’s said, “would only consent to meet him on such terms as would result in the certain destruction of one, or both.” (McCarty had suggested that they fight with pistols at point-blank range on top of a keg of gunpowder.) In Europe, the honor of the duellist was a concept that ennobled and abstracted violence. In America, it was a concept that empowered and invigorated it.

This practice was fuelled by a principle of common law, traced brilliantly by the historian Richard Brown, in his book “No Duty to Retreat.” In English common law, there was an old concept that, if you were engaged in conflict and killed someone, to prove self-defense you had to demonstrate that your back was—in most cases, literally—against the wall. You had a “duty to retreat.” In America, the new concept was that you had no duty to retreat—indeed, you had an obligation not to retreat. You were more or less required to blast away at anyone who approached you with, as you saw it, ill will. You didn’t have to show that you had tried to escape the confrontation. In 1856, Texas law, Brown writes, gave private citizens “wide discretionary powers to kill their fellow citizens legally and with impunity.”

This violence-encouraging doctrine has persisted, and so, too, has the reasoning of the judicial decisions that established it. There is no invocation of natural law; the argument isn’t that all men have an inherent right to kill when threatened. The appeal is, rather, to a kind of implicit cultural law: it is not in the American character to retreat. Beneath the surface of the liberal state and the legal rules designed to limit violence and to grant a monopoly on its use to a freely elected government, there is a national character that has to be protected—or, perhaps, invented. Appealing to that shadow nation impels the romance of violence in American life, and gives it practical and legal sanction as well. The legal liberal America is treated as a flimsy effigy, without the spirit to do the things that true Americans do—above all, act out violently with guns. And that identity is regarded as more worthy of protection than their citizenship.

Abraham Lincoln discussed this romanticization of violence in 1838, in one of his earliest public speeches, “Address Before the Young Men’s Lyceum of Springfield, Illinois.” What, Lincoln asked, threatened the well-being of American democracy? Only one thing: vigilante violence, “the increasing disregard for law which pervades the country; the growing disposition to substitute the wild and furious passions in lieu of the sober judgment of Courts.” He detailed the epidemic of violence and then located its cause in the need for what we would now call identity politics. Constitutional institutions might be equitable, but they were lacking in (and it’s striking that Lincoln used exactly this word) “authenticity”—the dry, rational legal system that the revolution had insured could never satisfy Americans’ need for an emotional connection with the past and with each other.

Lincoln’s own call, in response, was for an ever more radical rationalism: “Reason, cold calculating unimpassioned reason, must furnish all the materials for our future support and defense.” This was the doctrine underlying the Civil War, and it also makes clear Lincoln’s readiness to go to war on behalf of what seemed, to outsiders, like a puzzlingly arid legal principle: that the Union was not dissoluble. But he put his finger on why—with every fact pointing to the truth that the more armed men we have, the more homicides result, to the inarguable reality that more guns always mean more deaths—we persist so stubbornly in holding weapons dear.

In plain English, it’s part of the cultural foundation of the country. Stand Your Ground, as it’s now called, or “no duty to retreat,” as it was called back in the day, is irrational, because it’s meant to be. Attorney General Eric Holder’s blasting of Stand Your Ground strikes something deep-seated, no matter how twisted. Those of us who are haunted by the sight of violence struggle to understand why, in the face of so much evidence, irrationality is allowed to rule. Lincoln’s answer was that it’s because the symbolic identity that guns provide matters more than the rational calculation of the harm that they do. When, Lincoln wondered, would Americans outgrow this feeling? In 1838, he thought it would happen soon. And here we are, still wondering.

Photograph: Library of Congress.