Chapter 11 — Part I: The Creed — Article IX: The Holy Catholic Church; the Communion of Saints
Section 35. Should anyone object that the Church is content with one Head and one Spouse, Jesus Christ, and requires no other, the answer is obvious. For as we deem Christ not only the author of all the Sacraments, but also their invisible minister -- He it is who baptises, He it is who absolves, although men are appointed by Him the external ministers of the Sacraments -- so has He placed over His Church, which He governs by His invisible Spirit, a man to be His vicar and the minister of His power. A visible Church requires a visible head; therefore the Saviour appointed Peter head and pastor of all the faithful, when He committed to his care the feeding of all His sheep, in such ample terms that He willed the very same power of ruling and governing the entire Church to descend to Peter's successors.