Three weeks ago, it may have sounded far-fetched to claim that the nation has been in a 150-year process of sorting through the cause and meaning of the Civil War. But the tragedy in Charleston, S.C., has helped provide clarity about the meaning of the Civil War for us today.

For historians, the major questions about the cause of the war have largely been settled. One need only read the statement of Alexander Stephens, vice president of the Confederacy, to understand what lay at the heart of the rebel government: “Its foundations are laid, its cornerstone rests, upon the great truth that the negro is not equal to the white man; that slavery, subordination to the superior race, is his natural and normal condition.”

Yet until last week, the reasons for the war were still deeply embedded in our political discourse, especially concerning the meaning of the Confederate flag. Those who defend the flag see it as a symbol of Southern heritage (even though 40 percent of its population on the eve of the war was African-American) and the war as a contest over states’ rights or as a sectional conflict. Yet people who deny the primacy of slavery as the cause of the war deny the great paradox of slavery and freedom that plagued the nation from its beginning.

Dylann Roof surely did not act on behalf of white Southerners as he murdered nine people in the sanctuary of Mother Emmanuel, but his actions are a grim reminder that for more than 100 years following the war, Southern states translated racism into politically and morally sanctioned violence against black citizens.

It is convenient to make heroes out of the flawed human beings who fought to preserve slavery; uncomplicated histories make for simple and convenient explanations of present problems. The events in Charleston give the lie to the myth of the Lost Cause of the South and confront us with the ugly reality and cruel legacy of the Confederacy and Jim Crow.

But when the victims’ families followed Martin Luther King’s principle and met physical force with soul force, they gracefully and powerfully exposed the illusion of virtue upon which the Lost Cause depended.

Challenging the narrative of the Lost Cause was the not the main purpose of the remarkable act of forgiveness that the nation witnessed in Charleston three weeks ago. The possibility of true redemption, however, was its result. By dipping into what the president called their “reservoir of goodness,” the families of the victims have created a transformative moment of empathy that has prompted many defenders of the flag to reassess its meaning. Hopefully, by considering the experience and history of their neighbors, those who speak of “heritage” will think of black people, too, as Southerners.

It would be naive to think that our shared outrage and amazement at the events in Charleston will result in overnight change. Racism, the cause for which the Confederacy fought, persists today. But maybe now, when people talk about the Confederate battle flag, they’ll say “Yes, but what about Charleston?” Perhaps our sense of history changed, so that we better understand how slavery and Jim Crow cast a long shadow over our politics and our society. Perhaps, too, we can insist on finishing our own work in the spirit of Lincoln and those who died in Charleston. “With malice toward none, with charity for all, with firmness in the right as God gives us to see the right, let us strive on to finish the work we are in, to bind up the nation’s wounds, to care for him who shall have borne the battle and for his widow and his orphan, to do all which may achieve and cherish a just and lasting peace among ourselves and with all nations.”

Russell Motter is a teacher of U.S. History and African-American Studies at ‘Iolani School.