This collection of essays was presented to Professor Soren Giversen on his 65th birthday, 9 January 1993. Their common theme is ancient Gnosticism and its importance to the social, cultural and religious development of the Mediterranean world from Hellenistic to Roman times. Our knowledge of Gnosticism has recently been enriched by the discovery of previously unknown Gnostic texts preserved in Coptic manuscripts and published by Soren Giversen and others. These texts form the point of departure for several of the essays; others deal with Marcion, early Christianity and Judaism and their attitude to crucial Gnostic issues.