Gnostic beliefs presented themselves as a major challenge to Irenaeus of Lyons (Against Heresies, ca. A.D. 180), Hippolytus of Rome (the presumed author of the Elenchos Against All Heresies, post-A.D. 222), and Epiphanius of Salamis (Panarion, A.D. 374-77). What was at stake for them were life-and-death issues; the nature of Christianity and the question of truth. While recent manuscript finds shed new light on gnostic thought, the writings of the heresiologists are still indispensable--for knowledge of gnostic teaching but also of "what certain influential authors in the...