Secret Groups in Ancient Judaism proposes a new approach to the understanding of many Jewish groups and sects from the last centuries BCE and the first centuries CE. Michael Stone argues that the known ancient Jewish groups-the Qumran covenanters, Josephus's and Philo's Essenes, and Philo's Therapeutae-can be viewed as societies at the heart of whose existence were esoteric knowledge and practice. Guarding and transmitting this esoteric knowledge and practice, Stone argues, provided the dynamic that motivated the social and conceptual structure of these groups. Analyzing these groups as secret societies enables us to see previously latent social structural dimensions, and provides many new enriching insights into the groups, including the Dead Sea covenanters. Drawing on sociological analyses of secret societies, Stone also compares these Jewish groups with mystery religions of the contemporary Greek and Roman world, and of early Christianity. His approach casts a powerful new light on ancient Jewish religious groups and highlights unstudied aspects of the world of Christian origins.