But avoiding the words that people didn’t use back then is ultimately just a mechanical problem. A Princeton history graduate student, Ben Schmidt, has actually written a program that tags all the phrases in a script that don’t appear in the books of its era. The bigger challenge is to convey the meanings of the words that people did use, especially when they resonate differently now. “Equality,” “prejudice,” “race” itself — how can you have mid-19th-century characters use words like those without anachronistically evoking the connotations they have for us? To many of Lincoln’s contemporaries and even his allies, “equality” still evoked alarming echoes of the French Revolution. To speak of “race equality” implied not just that people should all be treated alike, but that the races really were morally and intellectually equivalent. That seems self-evident to us, but it was an extreme and dubious proposition to all but a few radical Republicans, like Thaddeus Stevens. Lincoln himself almost certainly didn’t believe it, nor did the prominent scientists of the age. In fact, the phrase “race equality” was the phrase the defenders of slavery threw at Republicans to charge that they wanted to raise Negros to the same status as whites and encourage miscegenation — charges the Republicans indignantly and sincerely denied.