DIOCESE. - In the ecclesiastical order it is that territory, well defined in its extent and in its boundaries, which is governed by a bishop with ordinary power according to the norms of law (cf. CIC, cann. 215 and 329); it generally takes its name from the place where the cathedral church stands, the mother of all the other churches and where the bishop himself has his habitual residence. Such a name derives from Roman public law: in the Constantinian age, in fact, the name of d. designated a broad circumscription, which comprised a certain number of provinces and was governed by a vicar. In Christian antiquity, however, today's d. was commonly called Church; so that by this term was indicated not only the universal Church but also the individual particular Churches; besides the buildings in which the Christian community assembled. A little later the d. was indicated by the name of parish, until finally the term d. prevailed as exclusive. The origin of the d. lies at the beginnings of Christian propaganda. For while the Palestinian territory was under the direct government of the apostolic college, St. Paul took care to establish, in his journeys through the Roman Hellenic world, Christian communities in the urban centers, placing at the head of each a college of presbyters assisted by deacons: he in turn was assisted by trusted disciples who, when needed, took his place among those communities. St. Paul was certainly not the only great missionary among the Gentiles; St. Peter too, having left Palestine and beginning from Antioch, extended his missionary activity. At their death the disciples continued their work in the territories for which they had received a special mission, so that the apostolic succession was not interrupted. And since in the cities the most numerous centers of the faithful had been formed, here the leaders of the individual Christian communities took up their seat under the name of bishops. In this way, with the progressive expansion of the propaganda, in every city there was a bishop assisted by a clergy equal in rank and authority to those of the other cities, apart from that personal prestige which could derive to some among these bishops from special gifts of holiness or organizational ability. Hence it came about that in the regions where the number of cities or of inhabited centers of some importance was greater, the number of d. also proved greater, so much so that it became necessary to intervene (as in Africa) lest these multiply too much to the detriment of discipline.
It is natural that the boundaries of the d. should for the most part coincide with the boundaries of the individual urban territories; and that the bishoprics of the lesser centers should gravitate by preference toward the more important centers, that is, toward the capital city of the province within which they were included and with which particular economic or political interests existed. When in the West Christianity spread into countries inhabited by barbarians or reconquered regions where the invasions had upset every civil order, recourse was had directly to the pope for the constitution of the regular ecclesiastical hierarchy and for the division of the country into d. according to the common discipline; a task which the pope then carried out by means of legates sent on the spot, and even today brings to completion by means of the Roman dicasteries, as soon as in a heretical or pagan country solid nuclei of Catholics have been formed. In fact, according to the discipline in force, only the Roman Pontiff erects and suppresses d., divides the territory of those that prove too vast and populous, unites in perpetuity or temporarily two d. under a single bishop, changes their boundaries by detaching a part of the territory to incorporate it into another (cf. CIC, cann. 215-16). The first requirement for the constitution of a d. is that a cathedral church be erected in it, a sufficient and dignified residence for the bishop in the most important and suitable place for administration, and that provision be made for the support of the bishop himself and of his clergy, that the formation of the sacred ministers be possible in a local or central seminary, that the division of the diocesan territory into parishes with well-determined boundaries be at least begun. For, according to the law in force, a regularly constituted d. that is not subdivided into parishes is inconceivable. In all d. of ancient foundation there is a college of priests for the liturgical officiality of the cathedral church (Cathedral Chapter: v.) which assists the bishop in the government of the d. in circumstances determined by the norms of law. But for the dispatch of current affairs the bishop himself is assisted by a group of officials (vicar general, chancellor, etc.) who constitute the diocesan curia.
In the d. of the missions it is possible that a part of the territory is not divided into parishes, but entrusted directly to missionaries as cooperators of the Ordinary.
The individual d., then, are either directly subject to the Roman Pontiff, or grouped into ecclesiastical provinces in each of which one of the bishops, for the most part the one of the most important, most illustrious or most ancient see, with the title of metropolitan (metropolitan see) or of archbishop, holds a special presidency over the others with authority specifically defined by the canon laws (v. METROPOLITI). These are called suffragan sees. There are, however, archiepiscopal sees without suffragan d. Those are called titular sees (episcopal and archiepiscopal) which now subsist only as a historical memory, because they no longer have either a subject Catholic people or an ecclesiastical organization, and sometimes no longer even exist as an inhabited place, but which continue to be conferred by the Holy See on prelates who are thereby invested with the episcopal character. This happens so that they may perform the sacred functions reserved to bishops, whether as auxiliaries of residential bishops or as vicars of the Holy See in territories where the ecclesiastical hierarchy is not yet regularly constituted, or so that they may sustain with greater dignity and authority important offices, such as those of nuncios or apostolic administrators, of military bishops, or even for other particular and personal reasons.
Nowadays among the Orientals many d. are not only circumscribed within a determined territory, as in the West, but are also limited to a part of the population dwelling there, that is, to that part which follows a particular rite and belongs to one of the nationalities that make up the entire population. Thus the Catholic bishops of the Byzantine rite have no jurisdiction over the faithful of the Latin rite dwelling in their territory and vice versa; the Armenian bishops have no jurisdiction over the Melkite or Syrian faithful, etc., who are governed by their own proper hierarchy.
Bibliography2 works
Pio Paschini
Although the matter of the delimitation of d. is of exclusive competence of the Church, nevertheless it often grants the State some faculty of interference (v. CIRCOSTRIZIONI ECCLESIASTICHE).
One of the most notable examples of this in the more recent concordats is contained in articles 16-17 of the Italian concordat. By these it was established that the Holy See and Italy should proceed in agreement "by means of mixed commissions, to a revision of the circumscription of the dioceses, with the aim of making it correspond as far as possible to that of the provinces of the State," proceeding with the reduction of the dioceses as they became vacant (for various reasons, this norm has had little practical application), and without suppressing the titles of the dioceses or the chapters, but grouping the dioceses in such a way that their chief towns corresponded to those of the provinces. It was further established that, in any case, no part of the territory subject to the sovereignty of the Italian State should depend on a bishop whose see was located in territory subject to the sovereignty of another State; and that no diocese of Italy should include zones of territory subject to the sovereignty of another State. The modifications which, after the arrangement mentioned above, should in the future be made to the circumscriptions of the dioceses, will be ordered by the Holy See after agreements with the Italian government and in observance of the same principles, except for the small rectifications of territory required by the good of souls.