In his 1962 book on the Civil War, Edmund Wilson declared that the usual arguments for fighting it — God, justice, and the defense of freedom — were simply covers for a bestial, atavistic impulse. Man, he wrote, was no different from “a sea slug … gobbling up smaller organisms through a large orifice at one end of its body.” It was a reductive view that led Wilson to find a disturbing moral equivalence between Union and Confederacy, but it provocatively challenged America’s faith in its special destiny.

Why do we fight? It’s an old but timely question. In “Age of Lincoln” (Hill and Wang, 420 pages, $27), Orville Vernon Burton takes aim at the tendency to cite providence as an excuse for bloodshed. Unlike Wilson, Mr. Burton believes that war, at root, is about more than biology — its causes are imbedded in the thought and culture of the age. For him, political experience — and certain remarkable individuals — can help guide the ways we comprehend and justify violence.

“The Age of Lincoln” takes up roughly where Arthur Schlesinger’s magisterial history of antebellum America, “The Age of Jackson,” leaves off. The first part of Mr. Burton’s book is a social, economic, political, and intellectual history that pays close attention to the suffering of a familiar cast of subalterns: women, blacks, immigrants, and American Indians. But gradually the exploration becomes more original.

Wherever he looks, Mr. Burton finds traces of millennialism, the radical belief that Americans, God’s chosen people, could expedite the reign of Christon earth by living piously and remaking society according to His will. “Millennialism permeated antebellum political debate, undergirded the presumption of Manifest Destiny, and buttressed the understanding of honor,” Mr. Burton claims.

He then makes a still bolder claim: The millennialist’s worldview played a critical role in precipitating the Civil War. For abolitionists, “there could be no heaven on earth with the evil of slavery embedded in the very fabric of the nation,” while pro-slavery Southerners believed “their orderly plantation society reflected the will of God.” As attempts to broker a compromise on slavery’s western expansion faltered in Congress, righteousness on both sides “eroded any middle ground, as constituencies rallied to intransigent positions.” North and South went to war, each with God on its side.

The hero of Mr. Burton’s history is President Lincoln, whom the author neatly portrays as both a product and critic of the nation’s millennial complex. Kentucky-born, Lincoln’s “southern sense of honor” tied him with the old order and fortified his unyielding stand against secession (challenged by a Baltimore delegation to let the South go in peace, Lincoln replied, “You would have me break my oath and surrender without a blow. There is … no manhood or honor in that.”)

But Lincoln’s personal faith was distinctly non-millennialist, predicated on the unknowability of God’s designs. Coupled with a deep reverence for the Constitution, it allowed him to espouse a humbler, more practical conception of liberty, stripped of pious yearning and based on the idea of equal rights under the law. This was the “new birth of freedom” that Lincoln prophesied at Gettysburg. His vision, Mr. Burton argues, freed the slaves, gave blacks the vote, and also laid the framework for a postwar society more focused on earthly progress than heavenly perfection. Such was the 16th president’s vast legacy. If it were regularly betrayed in the years that followed — by Gilded Age inequalities in the North, and the rise of Jim Crow in the South — it would nonetheless become thoroughly digested into the American self-understanding.

“The Age of Lincoln” is a dazzling performance, but some of its claims are hard to accept. Mr. Burton’s notion of millennialism, for instance, strains under the multitude of meanings it is made to bear. Readers are left with little sense of what separated religious radicals from mere partisans, or the specific steps by which North and South became so violently opposed.

More grievously, Mr. Burton accords such importance to Lincoln that at times he appears less of a human than a heuristic device for explaining the transition from antebellum to modern America. We hear, for instance, that the Populists, a political party that rose to prominence 25 years after Lincoln’s death, were “the last of Lincoln’s people,” and that during Reconstruction there was but one Supreme Court justice who “articulated Lincoln’s vision of freedom.” Such statements obscure the fact that the notion of civil equality has always been a highly debated proposition in America — not simply the brainchild of one man.

The writing in “Age of Lincoln” can be a slog. Mr. Burton, whose previous works have focused mostly on Southern history, has chosen the lens of social-intellectual analysis, forgoing the felicities of a straightforward narrative. But it is clear that he intends the book for a broad audience. If he occasionally seems to read 21st-century American fundamentalism — à la the Radical Right — into his notion of millennialism, his work still provides remarkably fresh insights into this perpetually crucial period American history.

Mr. Reynolds, a fellow at the Center of the Study of the Presidency, last wrote for these pages on the American colonial frontier.