Independence Day arrived this year during a period of intense political polarization, anger and distrust, potentially jeopardizing the ideals for which the American Revolution was fought.

That’s a problem, but it also signals an opportunity. Nations benefit from the unifying effects of shared memories — especially if those memories reflect a commitment to ideals. The revolution was inspired by two such ideals: self-government and human liberty.

To understand the current importance of that claim, a good place to look is a speech by Abraham Lincoln — not by the president who emphasized the better angels of our nature, but by a largely unknown 28-year-old, speaking in 1838 before the Young Men’s Lyceum in Springfield, Illinois, under the ambitious title “The Perpetuation of Our Political Institutions.”

Even as a young man, Lincoln was obsessed by founding principles, and as he would 25 years later at Gettysburg, he focused on the foundations of the American experiment in self-government.

The occasion for the speech was what Lincoln saw as a serious danger, not from abroad but from “amongst us.” Two weeks before, parts of the nation had reeled from a gruesome murder in St. Louis. As Lincoln put it:

“A mulatto man, by the name of McIntosh, was seized in the street, dragged to the suburbs of the city, chained to a tree, and actually burned to death; and all within a single hour from the time he had been a freeman, attending to his own business, and at peace with the world.”

Lincoln insisted that black lives matter. Decades before ratification of the 14th Amendment to the Constitution and its equal protection clause, which followed the Civil War, Lincoln insisted on the equal protection of the laws.

But Lincoln had a broader claim, involving the importance of respect for the law, and of inculcating it in people’s hearts. That idea should “be taught in schools, in seminaries, and in colleges; let it be written in Primers, spelling books, and in Almanacs; let it be preached from the pulpit, proclaimed in legislative halls, and enforced in courts of justice.” He argued that reverence for the law, and for the rule of law, should become “the political religion of the nation.” ...