Arthur Middleton on the bishop as the focus of unity
Ignatius and Irenaeus saw the bishop’s office as a focus of unity, in space and in time, because succession and continuity are integral to apostolicity and catholicity. It is much more than an empirical unity. Cyprian is emphatic about this existing church principle because of his own episcopal circumstances. The Paschal Synod at Carthage (251) is concerned with the lapsed and the schisms at Rome and Carthage. They were intimately connected, but the latter concerns us here.
The De Unitate lays down the principles, while the letters [Epp. 41; 44; 48, to Cornelius; Ep. 51, to Antonian; Ep. 54, to Cornelius] demonstrate their practical application. His primary concern is the unity of a single particular church, which is secured by there being but one bishop in a city [Ep. 54.5].
The collegiality of the episcopate is what makes it singular in function throughout the whole Church, where each member exercises episcopal authority in harmony. Hence, because the episcopate is united, the whole Church is one, and that oneness is made visible by the mutual intercourse and common action of bishops throughout the world.
This sacramentum unitatis is more than a practical and empirical entity, because it is of divine appointment. For Cyprian, it stems from the gift of the keys to Peter that he might be the foundation of the Church, and though the other apostles were to share a power and authority equal to that of Peter, all are based on him. The bishops are exactly what the apostles were, and their authority is symbolized as the cathedra Petri, a phrase that seems to be formed on the analogy of ‘Moses’ Seat’ in Matthew 23.
This term cathedra Petri is not found in patristic literature before Cyprian, but in Tertullian [De Praescrip. 36], the term cathedrae apostolorum is used of those churches actually founded by apostles, such as Antioch and Ephesus. The ambiguous term cathedra Petri was used to describe the Roman Church from early times.
For Cyprian [Ep. 39], this is the ‘one chair founded on Peter,’ which is occupied by the bishop in every particular church. In De Unitate ch.4, the cathedra Petri is clearly identical with the una cathedra, which is unquestionably the bishop’s seat of authority, the seat of the undivided episcopate. At Rome this was the seat of Peter.
‘That he might set forth unity, he arranged by his authority the origin of that unity, as beginning from one. Assuredly the rest of the apostles were also the same as was Peter, endowed with a like partnership both of honour and power; but the beginning proceeds from unity…
‘And this unity we ought firmly to hold and assert, especially those of us that are bishops who preside in the Church, that we may also prove the episcopate itself to be one and undivided. The episcopate is one, each part of which is held by each one for the whole. The Church also is one, which is spread abroad far and wide into a multitude by an increase of fruitfulness…’ [De Unitate, 4, 5].