“It has been 20 years since the historian Annette Gordon-Reed published “Thomas Jefferson and Sally Hemings: An American Controversy,” a book that successfully challenged the prevailing perceptions of both figures. In a piece for The New York Times Book Review, submitted just before the tragic events in Charlottesville, Va., Gordon-Reed reflects on the complexities that endure in our understanding of Hemings and the language we use to characterize her.”