...“One cannot question the genuineness of Jefferson’s liberal dreams,” writes historian David Brion Davis. “He was one of the first statesmen in any part of the world to advocate concrete measures for restricting and eradicating Negro slavery.” But in the 1790s, Davis continues, “the most remarkable thing about Jefferson’s stand on slavery is his immense silence.” And later, Davis finds, Jefferson’s emancipation efforts “virtually ceased.” Somewhere in a short span of years during the 1780s and into the early 1790s, a transformation came over Jefferson. The very existence of slavery in the era of the American Revolution presents a paradox,...