List of works referred to in abbreviated form. 11 Chapter I: The foundations of mediaeval dualism in the period of late antiquity. 21 Chapter II: The Paulician movement in Byzantium. 32 Chapter III: The rise of a heretical movement in the First Bulgarian Empire. 41 Chapter IV: The Bulgarian Bogomil heresy as portrayed b Cosmas the Presbyter in his Sermon against the Heretics. 50 Chapter V: The Bogomil heresy and Byzantine rr. onasticism. 67 Chapter VI: The Bogomils and Paulicians in conflict with the Byzantine state power. 78 Chapter VII: The Bogomil myth as presented by Euthymius Zigabenus. 84 Chapter VIII: Byzantine Bogomilism after Alexius Comnenus. 96 Chapter IX: The western ideal of the vita apoBtoZica and the heretical apostles from the East. 103 Chapter X: The emergence of the Cathar churches and their relations with the Christian East. 127 Chapter XI: The dualist doctrines as seen by western authors . . The myth and the ethics. 133 Chapter XII: Catharism and the western world. 147 Chapter XIII: The beginnings of heresy in Bosnia. 162 Chapter XIV: The cUlmination of the fight against heresy in Western Europe. 167 Chapter XV: Heresy "in partibus Sclavoniae" - the crusade against Bosnia. 211 Chapter XVI: The struggle against the Bogomil heresy in Serbia under the Nemanjid dynasty. in the Second Bulgarian Empire. and in contemporary Byzantium. 225 Chapter XVII: Ecclesia Romana and "ecclesia Dei". 240 Chapter XVIII: The end of the Cathar sect in western Europe. 276 Chapter XIX: The "Bosnian Church".