1. Though populations are different in different dioceses and cities, still, as there is one Church, there must be one Christian people. As then in the spiritual people of one Church there is required one Bishop, who is Head of all that people; so in the whole Christian people it is requisite that there be one Head of the whole Church.*
2. One requisite of the unity of the Church is the agreement of all the faithful in faith. When questions of faith arise, the Church would be rent by diversity of judgements, were it not preserved in unity by the judgement of one. But in things necessary Christ is not wanting to His Church, which He has loved, and has shed His blood for it: since even of the Synagogue the Lord says: What is there that I ought further to have done for my vineyard and have not done it.? (Isai. v, 4.) We cannot doubt then that by the ordinance of Christ one man presides over the whole Church.
3. None can doubt that the government of the Church is excellently well arranged, arranged as it is by Him through whom kings reign and lawgivers enact just things (Prov. viii, 15). But the best form of government for a multitude is to be governed by one: for the end of government is the peace and unity of its subjects: and one man is a more apt source of unity than many together.*
But if any will have it that the one Head and one Shepherd is Christ, as being the one Spouse of the one Church, his view is inadequate to the facts. For though clearly Christ Himself gives effect to the Sacraments of the Church, -- He it is who baptises, He forgives sins, He is the true Priest who has offered Himself on the altar of the cross, and by His power His Body is daily consecrated at our altars, -- nevertheless, because He was not to be present in bodily shape with all His faithful, He chose ministers and would dispense His gifts to His faithful people through their hands. And by reason of the same future absence it was needful for Him to issue His commission to some one to take care of this universal Church in His stead.* Hence He said to Peter before His Ascension, Feed my sheep (John xxi, 1) and before His Passion, Thou in thy turn confirm thy brethren (Luke xxii, 32); and to him alone He made the promise, To thee I will give the keys of the kingdom of heaven (Matt. xvi, 19). Nor can it be said that although He gave this dignity to Peter, it does not pass from Peter to others. For Christ instituted His Church to last to the end of the world, according to the text: He shall sit upon the throne of David and in his kingdom, to confirm and strengthen it in justice and judgement from henceforth, now, and for ever (Isai. ix, 7). Therefore, in constituting His ministers for the time, He intended their power to pass to posterity for the benefit of His Church to the end of the world, as He Himself says: Lo, I am with you to the end of the world (Matt. xxviii, 20).
Hereby is cast out the presumptuous error of some, who endeavour to withdraw themselves from obedience and subjection to Peter, not recognising his successor, the Roman Pontiff, for the pastor of the Universal Church.
4.75 : Of the Distinction of Orders
4.77 : That Sacraments can be administered even by Wicked Ministers