By Jeremy J. Tewell

Kent State University Press, $45

North and South were culturally dissimilar from the very outset of European settlement. And though it wasn’t the stain of slavery, in isolation, that precipitated the Civil War, no one with an ear to the past doubts that slavery as an idea preoccupied popular thinkers as much as it engaged political actors. Jeremy J. Tewell’s reflective and instructive new book puts the Declaration of Independence front and center, and tackles newspaper columnists, pamphleteers, and legislators who committed to the battle of words in the feverish years before men marched into battle.

In a republic where some people were enslaved owing to a presumed inferiority rooted in skin pigmentation and historical place of origin, was there any guarantee that some other factor might not, before long, be equally the determinant of one’s status in society? To a surprising number, it was not a mere hypothetical. In the 1850s, Abraham Lincoln, for one, insisted that to allow new western states to decide for themselves whether or not to abide the slave economy invited even northern states to reconsider their own local circumstances.

“By relinquishing control over slavery’s expansion,” Tewell intuits Lincoln’s conundrum, all America might be drawn into a state of “indifference to the future of human servitude.” Slavery and freedom would be comparable values, equally acceptable — and slavery not a moral wrong.

Lincoln was certainly a racist by modern standards, a politician whose pragmatic tendencies caused him to prefer black “self-deportation” (to use a controversial term of 2012). Indeed, he was carrying forward Jefferson’s dictum that slaves both deserved complete freedom and to be returned to their country of origin. As Lincoln looked back on Jefferson’s Declaration, he stated firmly that one could not make exceptions to that document’s principle of human equality: “Making exceptions to it?” Lincoln posed. “Where will it stop? If one man says it does not mean a Negro, why not another say it does not mean some other man?” No American could legitimately be subjugated to any other. Rights were universal. Wasn’t the United States of America meant, from its inception, to be morally consistent?

Southern defenders of the essential beneficence of the institution of slavery compared the protections their human property knew to the demonstrably squalid lives of northern laborers, who existed at the mercy of an economy far less flourishing than the cotton kingdom. “Free society!” exclaimed one Alabama newspaper. “What is it but a conglomeration of GREASY MECHANICS, FILTHY OPERATIVES, SMALL-FISTED FARMERS, and moon-struck THEORISTS.”

Louisiana’s Sen. Solomon Downs spoke to the morals of slavery: “Poverty is unknown to the Southern slave, for as soon as the master of slaves becomes too poor to provide for them, he SELLS them to others who can take care of them.”

Such outpourings may be hard to stomach, but the purpose of the historian is to reconstitute the moral boundaries of past societies. Both North and South lived in fear of what each defined as “chaos” or “tyranny.” Philosophers attempt to convey reason, but voting majorities respond most readily to their most irrational fears. As Tewell repeatedly makes clear, cultivated morality has always been critical in defining a republic. He quotes one of Jefferson’s most pithy and eloquent aphorisms: “Those who expect to be ignorant and free expect what never was and never will be.”

Is anyone suited for servitude? Lincoln’s law partner William Herndon said: “Slavery is right or it is wrong. If it is justice and right toward one race, so it must be to all.” If Southerners were willing to enslave Africans, he argued, then what objection could there be to the enslavement of whites whose prospects for advancement appeared equally remote? Tewell also invokes William H. Seward of New York: “If all are not equal and free, then who is entitled to be free, and what evidence of his superiority can he bring from nature or revelation?”

A Self-Evident Lie is not designed to pick a fight, but rather to reconstruct the argument that our forebears chose. Only certain Northerners committed themselves to the ideal of one “human family,” or were as deeply immersed in those questions of political morality that Lincoln, Jefferson Davis and their cohort were obliged to evaluate. The point to be made here is that the Civil War generation of leaders struggled with the nation’s past — with problems of logical consistency — as much as they critiqued their brethren on the other side of the conflict.

Thomas Jefferson could not have known what was to be unleashed in the 19th century when he promulgated equality as a “self-evident truth.” This book is a clear and concise synthesis of an idea, carried forward more than fourscore years, that deserves to command our attention.

Andrew Burstein is Charles P. Manship Professor of History at LSU, and co-author of Madison and Jefferson (now a Random House paperback). His website is http://www.andburstein.com.