Pope Leo the Great and the Ecclesiastical jurisdiction of Rome over Eastern Illyricum According to the Collectio Thessalonicensis

Introduction. The Collectio Thessalonicensis is a collection of documents compiled in the 9th century, which contains four letters of Pope Leo the Great (440–461) to Anastasius of Thessalonica and the episcopate of Eastern Illyricum. The correspondence took place in the 40s of the 5th century and reveals the policy of the Roman See in relation to this region. The aim of this article is to reconstruct the policy of Pope Leo the Great in relation to the Churches of Illyricum, aimed at consolidating over them the ecclesiastical authority of the See of Thessalonica and the supreme ecclesiastical jurisdiction of the Roman See. Methods. The work is based on the application of the historical-critical method of processing the text data of the sources used in the original Latin. Analysis. The article analyses in detail the content of three letters of Pope Leo – XXIII–XXV, according to the modern critical edition. The fourth letter, XXVI, has survived only partially and does not contain any significant information on the topic of interest to us. The studied letters are consistently analysed in order to identify the peculiarities of Pope Leo’s relations, on the one hand, with the primate of Thessalonica, Anastasius, and on the other hand, with the metropolitans and bishops of the provinces of Eastern Illyricum. In order to illustrate observations and conclusions, the article provides extensive translations and commentaries on excerpts from the studied letters, and an assessment of other available translations is given. Results. The letters of Pope Leo the Great studied in this work represent an important and, in fact, the final stage in the formation of the jurisdiction of the Roman See in Eastern Illyricum. The studied letters clearly demonstrate that the Metropolitan of Thessalonica had the power of a regional primate, personally delegated to him by the Pope, which is contrary to the general church practice of that time. Leo’s letters reflect the final stage of the transformation of the conciliar court in Eastern Illyricum into an ecclesiastical tribunal limited in the number of its members and headed by the Metropolitan of Thessalonica. The Papal See is designated in them for the first time as the highest appellate instance for Eastern Illyricum in matters of the episcopate. The provincial council now appears to be only the first instance for considering the case of the provincial episcopate: the second appears to be the Primate of Thessalonica, and the third is the Roman See. Funding. The research is carried out within the project “Black Sea Region and the Mediterranean World during Periods of Crisis and Changes in the Middle Ages”, funded by the Russian Science Foundation (no. 22-18-00167-П).