The Gnostic Trilogy is the best-known and most important work by the ascetic philosopher and teacher Evagrius of Pontus. For the first time since antiquity, this volume presents the work in its entirety, providing a fresh and comprehensive English translation of all three parts, in all their known ancient versions, both Greek and Syriac. Detailed explanatory notes, cross-references to Scripture, to ancient literature, and to Evagrius's other writings, as well as commentary on the translation techniques of the Syriac translators, provide the necessary resources for understanding this ancient and puzzling text.