Homily of the Unworthy Presbyter Cosmas Against the Newly Appeared Bogomil Heresy (10th Century)

Sermon Against the Heresy (Church Slavonic: Бесѣда на ересь ) is a polemical and didactic work of Old Bulgarian literature, written by Cosmas the Priest, a church writer close to Tsar Peter I of Bulgaria. Sermon bears the full title Homily of the Unworthy Presbyter Cosmas Against the Newly-Appeared Bogomil Heresy (Church Slavonic: недостоинаѥго козмꙑ презвѵтера бесеѣда на новоѩвивъшѫѭ сѧ ересь богоумилоу ), or, in other manuscripts, Sermon of Saint Cosmas Presbyter Against the Heretics, A Discussion and an Instruction from the Books of God. The treatise is recognized as the earliest and most complete work to tell of the nature of Bogomilism, its origins, and dualistic doctrine. As Catharism originated from Bogomilism, Sermon Against the Heretics is valuable as an insight into Catharism's Balkan predecessor. It is also an important source of life and society in 10th-century Bulgaria, which is described as suffering a major crisis, and the glorious days of Peter's father, Simeon the Great (r. 893–927), are long over. It has been preserved in 25 full copies, all from East Slavic sources, and 116 excerpts or compilations, some of which are of South Slavic origin. The earliest of the extant copies was made in the 15th century. As attested by the large number of copies, Cosmas' work was particularly popular in medieval Russia and Serbia. There, it was even used as a basis for writings against other heresies. 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 priest named Bogomil as its founder. 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. As Cosmas purposefully employed around 70 quotations from Apostle Paul to debunk the beliefs of Bogomils, he was very likely aware of the sect's ancestral ties to Paulicianism. The second part of the treatise contains Cosmas' criticism of contemporary Bulgarian society, with particular attention to the religious and social issues of the time. While Cosmas was a staunch supporter of the Bulgarian Orthodox Church's policies against Bogomilism, in the second section, he spares no criticism of that religious body's other practices. Cosmas accuses the Bulgarian abbots and bishops of greed, gluttony and neglect towards the congregation. He is also critical of hermits, whose popularity and influence Cosmas saw as inappropriate then. Cosmas hints that the emergence of Bogomilism should be blamed at least partially on the contemporary state of the Bulgarian Orthodox Church.