In 1966, the Supreme Court promulgated a new procedural rule for class actions in federal court. Amended Rule 23 was a considerably different mechanism than its predecessor. It was more inviting of class action litigation but also incorporated new mechanisms for protecting class members. This was not an unreasonable trade-off, and one can imagine a group of rule-makers—elite academics, federal judges, prestigious attorneys—peaceably striving to write a rule that could balance individual class members’ interests with the interests of the class as a whole. But this is not what happened. The Rule 23 of today is an accord between two rival sects of mid-century legal thinking.