COSMAS THE PRIEST. - A Bulgarian author of the 10th century.
He composed a treatise against the Bogomils (v.) of the First Bulgarian Empire, which is our principal source on that heresy and on him himself.
According to Vaillant, he was almost a contemporary of John the Exarch: he would have lived under Peter (927-69), son of Simeon the Great, and would have written immediately after the fall of Bulgaria under Byzantium (972).
The purpose of the book is to stem the enormous danger of the heresy and to combat abuses. The Treatise against the Bogomils is the principal work of ancient Bulgarian literature and, as it is, awkward but alive and sincere, surpasses its pedantic Greek models. It seems to ignore the Byzantine masters, while its horizon extends as far as Jerusalem and Rome. The title of "presbyter" which the author himself seems to attribute to himself would designate, according to Vaillant, the higher clergy. Since C. also uses it to designate Fathers of the Church, such as St. Athanasius, the title would even confirm the arguments of Gagov, according to which C. was a bishop.