Robert Pretty's introduction and translation of the Adamantius Dialogue provides access to the last important extant source about ancient Gnosticism(s) left unavailable in a modern European language. Little or no new material has come to light concerning some other groups than those reflected at Nag Hammadi - the Marconites, for example, and the followers of Bardesanes. These last mentioned groupings, together with the later Valentinians, are the very ones involved in the Adamantius Dialogue. The book is written in the form of a dialogue between a member of the Catholic Church and various heretical opponents who debate with him in turn.