Apologeticae sive Theologiae Fundamentalis, Tomus II (Pars Altera): Demonstratio Catholica

The Roman Church is apostolic both as regards origin and as regards succession.

1. The apostolicity of origin of the Roman Church is already evident. For on the one hand we have proved that that Church is apostolic in origin, whose head and centre are the see and the successor of Peter; on the other hand, however, we have shown that the Roman see is the see of Peter and that the Roman bishop is the successor of the prince of the apostles. Hence all particular churches, although recently founded, are mediately apostolic, provided that they are in communion with the Roman see, which is immediately apostolic.

2. The apostolicity of succession of the Roman Church is manifest with the same evidence. For we have also proved this: that the criterion of the apostolic succession of the pastors of individual churches is union with the successor of Peter, i. e. with the Roman pontiff. As many pastors of the whole world as remain united with the Roman pontiff have succeeded the apostles in an unbroken series and by a legitimate mission.

Therefore the Roman Catholic Church, although separated from the apostles by nineteen centuries and scattered throughout the whole world, is nevertheless wholly apostolic both as regards origin and as regards succession. On the contrary: