As one of the small tribe of writers who produce both history and historical fiction, I’ve been gratified and surprised that crossing that line enriches both for me. Why? The silence.

We never know enough to tell a past story completely. Take James Madison or Aaron Burr, two men I’ve written about. They accomplished extraordinary deeds, yet each left but a few boxes of written records (especially the secretive Burr). Worse, written recollections may be wrong or reflect biases, while other sources are slim: we can only walk through landscapes that they knew, read what they read, and view objects they used. Compare those sources to the constant self-awareness that a fiction writer works with, then add in the surroundings and context, which the author knows intimately. The hush of history can be a pallid competitor with the cacophony of life as we live it.

Historical fiction can fill the silence. With my novel The Lincoln Deception, I started with a deathbed story: in his final days, the prosecutor of John Wilkes Booth’s coconspirators confided that he had learned a secret during that case that “could destroy the republic.” But he took the secret of Lincoln’s killers to his grave. The story wouldn’t let me go. Was the prosecutor hallucinating, or had he spent decades protecting the nation from

an incendiary secret? What about the Lincoln assassination, after all? Did it really start and end with Booth, a 26-year-old actor? His gang tried to kill Vice President Andrew Johnson, Secretary of State William Seward, and General Ulysses S. Grant, as well as Lincoln—had they succeeded, the result would have been a coup d’état, not an assassination.

These questions became the spine of The Lincoln Deception, which imagines a character hearing that deathbed disclosure and setting off to investigate it. Through fiction, I could take the reader on a journey that tested the prevailing understanding of the Lincoln murder. Of course, I had to make up the ultimate secret, but readers are on notice to judge for themselves whether I have filled that silence correctly.

For The Wilson Deception, I turned to the Paris Peace Conference of 1919, which ended “the war to end all wars” with “the peace to end all peace,” seeding future conflicts from World War II to the Syrian civil war. The book gives voice to American president Woodrow Wilson and French premier Georges Clémenceau, who speak with arrogance and complex motives that lead them astray.

Other figures fill out the story. There was Secretary of State Robert Lansing, banished by the president from the peace talks yet also uncle to the brilliant Dulles brothers. Allen Dulles, a 25-year-old spy, became Wilson’s closest aide at the conference, while the slightly older John Foster Dulles helped craft the ruinous terms imposed on Germany. I probably couldn’t have made up such characters; had I, readers might not have believed them.

As for race issues—the fictional protagonists of The Wilson Deception are white and black—America hatefully mistreated its own black soldiers in 1919, and the Second Pan-African Congress met in Paris in 1919 and included W.E.B. DuBois.

Writing historical fiction enriches history writing, sensitizing authors to the human side of a story and the textures of daily life. What tunes did people hum? How dirty were they? How did they dispose of waste—human and other types?

To explore Madison’s personality and experience in Madison’s Gift, my latest nonfiction book, I used the grueling nature of travel to illustrate the patience and resourcefulness required in his era. A flood-choked river forced Madison to float his carriage across in three pieces, then cross on a swimming horse. Often portrayed as a dry creature of intellect, Madison liked off-color jokes and roughhoused with wife Dolley into their senior years. She sometimes rampaged through their home with him on her back.

Writing historical fiction can lead writers of history to powerful backstage moments, but it does not relax the essential requirements of careful documentation and thoughtful, fact-based interpretations. There is no license to pass off even a single detail of the writer’s imagination as history. Still, both history and historical fiction have the same end: examining human nature and experience—perhaps even understanding them.

David O. Stewart’s second historical novel, The Wilson Deception, was published by Kensington in September. Madison’s Gift, a study of the five central partnerships of James Madison’s career, was published in February by Simon & Schuster.