Catholic Diocese
The Canon Law of the Catholic Church defines a diocese as "a portion of the people of God which is entrusted to a bishop for him to shepherd with the cooperation of the presbyterium, so that, adhering to its pastor and gathered by him in the Holy Spirit through the gospel and the Eucharist, it constitutes a particular church in which the one, holy, catholic, and apostolic Church of Christ is truly present and operative."[9]
Christianity was given legal status in 313 with the Edict of Milan. Churches began to organize themselves into dioceses based on the civil dioceses, not on the larger regional imperial districts.[3] These dioceses were often smaller than the provinces. Christianity was declared the Empire's official religion by Theodosius I in 380. Constantine I in 318 gave litigants the right to have court cases transferred from the civil courts to the bishops.[4] This situation must have hardly survived Julian, 361–363. Episcopal courts are not heard of again in the East until 398 and in the West in 408. The quality of these courts was low, and not above suspicion as the Bishop of Alexandria Troas found that clergy were making a corrupt profit. Nonetheless, these courts were popular as people could get quick justice without being charged fees.[5] Bishops had no part in the civil administration until the town councils, in decline, lost much authority to a group of 'notables' made up of the richest councilors, powerful and rich persons legally exempted from serving on the councils, retired military, and bishops post-AD 450. As the Western Empire collapsed in the 5th century, bishops in Western Europe assumed a larger part of the role of the former Roman governors. A similar, though less pronounced, development occurred in the East, where the Roman administrative apparatus was largely retained by the Byzantine Empire. In modern times, many dioceses, though later subdivided, have preserved the boundaries of a long-vanished Roman administrative division. For Gaul, Bruce Eagles has observed that "it has long been an academic commonplace in France that the medieval dioceses, and their constituent pagi, were the direct territorial successors of the Roman civitates."[6]
Modern usage of 'diocese' tends to refer to the sphere of a bishop's jurisdiction. This became commonplace during the self-conscious "classicizing" structural evolution of the Carolingian Empire in the 9th century, but this usage had itself been evolving from the much earlier parochia ("parish"; Late Latin derived from the Greek παροικία paroikia), dating from the increasingly formalized Christian authority structure in the 4th century.[7]
As of April 2020, in the Catholic Church there are 2,898 regular dioceses: 1 papal see, 9 patriarchates, 4 major archdioceses, 560 metropolitan archdioceses, 76 single archdioceses and 2,248 dioceses in the world.