When David Souter was nominated by President Bush to the Supreme Court, he cited John Marshall Harlan as his model. It was an interesting choice. Admired by conservatives and deeply respected by his liberal brethren, Harlan was a man, as Justice William Brennan lamented, whose "massive scholarship" has never been fully recognized. In addition, he was the second Harlan to sit on the Court, following his grandfather--also named John Marshall Harlan...