 "Sermon Against the Heretics" is divided into two sections, which may be seen as separate works due to their somewhat different topics.The first part presents details about various aspects of the Bogomil heresy and identifies a certain priest named Bogomil as its founder (though, Cosmas claims, it was actually an act of the devil himself).The first section of the treatise is a vehement criticism of Bogomilism and its disobedient followers, whom Cosmas accuses of contributing to the degradation of Bulgarian society.