DIOCESE, the sphere of a bishop's jurisdiction (from Gr. bco1Kr70 tS, "house-keeping," "administration"). In this, its sole modern sense, the word diocese (dioecesis) has only been regu larly used since the 9th century. The Greek word ScoLKAocs, from meaning "administration," came to be applied to the territorial circumscription in which administration was exercised. The word is equivalent to "assize-districts." But in the reorganization of the empire, begun by Diocletian and completed by Constantine, the word "diocese" acquired a more important meaning, the em pire being divided into twelve dioceses, of which the largest Oriens—embraced sixteen provinces, and the smallest—Britain f our (see ROME : Ancient History; and W. T. Arnold, Roman Provincial Administration, pp. 187, 194-196, which gives a list of the dioceses and their subdivisions). The organization of the Christian church in the Roman empire following very closely the lines of the civil administration (see CHURCH the word diocese, in its ecclesiastical sense, was at first applied to the sphere of jurisdiction, not of a bishop, but of a metropolitan. For exceptions see Hinschius ii. p. 39, note I. The word, how ever, survived in its general sense of "office" or "administration," and it was even used during the middle ages for "parish" (see Du Cange, Glossarium, s. "Dioecesis" 2).
The practice, under the Roman empire, of making the areas of ecclesiastical administration very exactly coincide with those of the civil administration, was continued in the organization of the church beyond the borders of the empire, and many dioceses to this day preserve the limits of long vanished political divisions. The process is well illustrated in the case of English bishoprics. But this practice was based on convenience, not principle; and the limits of the dioceses, once fixed, did not usually change with the changing political boundaries. Thus Hincmar, archbishop of Reims, complains that not only his metropolitanate (dioecesis) but his bishopric (parocliia) is divided between two realms under two kings; and this inconvenient overlapping of jurisdictions remained, in fact, very common in Europe until the readjust ments of national boundaries by the territorial settlements of the 19th century. In principle, however, the subdivision of a diocese, in the event of the work becoming too heavy for one bishop. was very early admitted, e.g., by the first council at Lugo in Spain (569), which erected Lugo into a metropolitanate, the consequent division of diocese being confirmed by the king of the second council, held in 572. Another reason for dividing a diocese, and establishing a new see, has been recognized by the church as duly existing "if the sovereign should think fit to endow some principal village or town with the rank and privileges of a city" (Bingham, lib. xvii. c. 5) . But there are canons for the punishment of such as might induce the sovereign so to erect any town into a city, solely with the view of becoming bishop thereof. Nor could any diocese be divided without the consent of the primate.
In England an act of parliament is necessary for the creation of new dioceses. In the reign of Henry VIII. six new dioceses were thus created (under an act of ; but from that time onward until the 19th century they remained practically un changed.
By the ancient custom of the church the bishop takes his title, not from his diocese, but from his see, i.e., the place where his cathedral is established. Thus the old episcopal titles are all de rived from cities.
See Hinschius, Kirchenrecht, ii. 38, etc. ; Joseph Bingham, Origines ecclesiasticae, 9 vols. (184o) ; Du Cange, Glossarium, s. "Dioecesis"; New English Dictionary (Oxford, 1897), s. "Diocese."