This volume in honour of Adelbert Davids, professor emeritus of Patristic studies at the Faculty of Theology of the Radboud University Nijmegen and former editor-in-chief of The Journal of Eastern Christian Studies, was first published in that same journal in 2008. As this issue is sold out the book is here reprinted in the companion series of Eastern Christian Studies. Heretics and Heresies in the Ancient Church and in Eastern Christianity opens with a biographical note (by P. Nissen) and contains eighteen essays by friends and colleagues of the honoree that all deal with one or another aspect of the crucial question of how the Early Church and the Eastern Church have defined heresy and orthodoxy. The contributors are B. Dehandschutter (heresy and the notion of tradition), A. Hilhorst ('heretical' martyrs), A. van den Hoek (Heracleon's hermeneutics), F. Ledegang (the Ophites), J. van Amersfoort (the Ebionites), K. Demoen (fourth-century thelogy on the notion of heresy), J. Leemans (Gregory of Nyssa on orthodoxy and heresy), J. Verheyden (Epiphanius' Panarion), D. Muller (persecution of heretics under Justinian), P.Van Deun (editio princeps of tractate CPG 7697,25 by Maximus the Confessor), A.A.R. Bastiaensen (the notion of perfidus/perfidia), M. Parmentier (editio princeps of CPL 560, a guideline against heretics), G. Bartelink (Cassianus's De incarnatione), D.W. Winkler (Nestorian controversy in the seventh century), H. Kaufhold (regulations against heresy and heretics in canon law in the Eastern Churches), H. Teule (Barhebraeus), F.B. Poljakow (traces of gnosticising thought currents in early twentieth-century Russia), B. Groen (dealing with anti-judaism in Byzantine liturgy today).