Oliver Wendell Holmes escaped death twice as a young Union officer in the Civil War. He lived ever after with unwavering moral courage, unremitting scorn for dogma and an insatiable intellectual curiosity. During his nearly three decades on the Supreme Court, he wrote a series of opinions that would prove prophetic in securing freedom of speech, protecting the rights of criminal defendants, and ending the Court’s reactionary resistance to social and economic reforms. As a pioneering legal scholar, Holmes revolutionized the understanding of common law. As an enthusiastic friend, he wrote thousands of letters brimming with an abiding joy in fighting the good fight. Drawing on many previously unpublished letters and records, Stephen Budiansky offers the fullest portrait yet of this pivotal American figure.