In the closing days of the 1956 term of the U.S. Supreme Court, Chief Justice Earl Warren turned to newly appointed Associate Justice William J. Brennan, Jr., for advice and counsel on four crucial cases that had deeply divided the Court. In United States v. DuPont, the chief justice asked Justice Brennan to write for the majority that narrowly blocked the merger between DuPont and General Motors. In Jencks v.United States, the chief justice designated Brennan to write a pathbreaking opinion obliging prosecutors to disclose exculpatory evidence. In Watkins v. United States and Sweezy v. New Hampshire, Brennan returned the favor, providing crucial support for the chief justice’s then-controversial opinions placing limits on McCarthy-era tactics of legislative investigating committees. The close collaboration between the two justices was the harbinger of a partnership that fundamentally altered American constitutional law.

When we celebrate the great Supreme Court justices who have shaped our constitutional tradition, we tend to concentrate on their individual achievements. On rare occasions, though, as with Justices Oliver Wendell Holmes, Jr., and Louis Brandeis, an intellectual bond between two justices is so intense, the justices’ shared impact on American law so significant, that their contributions may be appreciated in combination. The joint and several judicial careers of Chief Justice Earl Warren and Justice William Brennan, Jr., are one of the best cases in point.