Before railroad crossings had red lights, gates, and warning bells, they had a simple but effective sign: a wooden X with one board marked RAILROAD CROSSING and the other STOP LOOK AND LISTEN. The sign was invented in America in the early days of the automobile and quickly spread to the rest of the world—for a reason not flattering to the human species. Before the automobile, people traveled by horse, and the average horse has enough sense not to cross the tracks when a train is coming. The average motorist, not so much.

Horse sense is still rare among humans. So, a similar warning sign is needed for the danger now threatening a certain hard-won wisdom about the American colonies’ decisive break with Great Britain. This wisdom has been accumulated by generations of historians, biographers, political theorists, librarians, archivists, government agencies, philanthropists, and educators unafraid to correct, criticize, and confirm one another. It is broad, deep, inclusive, and open-ended. But right now, it is idling on the tracks in the path of a runaway locomotive.

Fueling that locomotive are two polarized versions of history. The first asserts that the principles of equality, liberty, and constitutional self-government were transparent lies, because the Revolution’s real purpose was to perpetuate slavery. The second defends those principles with understandable