Ben-Hur exists because a Union general lost an argument he did not know he was having. On September 19, 1876, Lew Wallace, a Civil War veteran still smarting from an unfair share of blame for the near-disaster at Shiloh, shared a train compartment to Indianapolis with Robert Ingersoll, the most famous agnostic orator in America. Ingersoll made a habit of testing new acquaintances on their faith, and for hours he pressed Wallace on the evidence for God, for heaven, for Christ, for every claim Christianity asked people to accept on trust.
Wallace considered himself a Christian in the ordinary, unexamined way many nineteenth-century Americans did: he did not attend church regularly, did not pray with any discipline, and by his own later account could not have defended a single one of his beliefs against a determined skeptic. Ingersoll's questions left him less certain of his agnosticism, in an odd sense, than of his own ignorance. Rather than simply reading his way to an answer, Wallace decided to write one: a novel set in the world Jesus walked through, following a fictional witness close enough to the events to make their reality, or their absence, concrete rather than abstract.
The book took him seven years. Ben-Hur: A Tale of the Christ, published in 1880, became one of the best-selling American novels of the nineteenth century, outsold in its own era only by the Bible itself. Ingersoll, who had hoped to win Wallace to skepticism, had instead supplied the occasion for one of the most widely read defenses of Christian faith his country ever produced.