The Roman Catholic Church is the true Church of Christ because it alone possesses the mark of apostolicity. Various Christian denominations, by their very formation, have denied both apostolic origin and apostolic continuity; all were born from a departure from the ancient Church and rebellion against the head of the Church. Their motivations and difficulties were diverse, but they have one thing in common: they do not listen to the Church (Ecclesiam non audire).
This is particularly evident in Protestant denominations, whose older representatives wanted to preserve apostolic continuity by arguing that there have always been reformers within the Church who acted as carriers of a parallel Protestant tradition. However, this is directly excluded by the Lord's command; He builds the Church on the rock foundation of Peter, sends His apostles with full authority, and remains with them until the end of the world. Those who listen to them will be saved, and those who do not will be damned. The ancient Church also interpreted His words in this way: those who were not in agreement with the Catholic Church and its head were excluded as not listening to the Church. The rebellion and negativity of heretics and schismatics throughout history are not enough to establish legal succession and continuity; denial is multifaceted and divisive, not constructive but destructive. If there were a line of extraordinary "reformers" alongside the legitimate successors of the apostles, the Church would have two parallel leaderships with no guarantee of harmonious cooperation; this would legalize chaos and division within the Church. Furthermore, where are the "signs" (miracles, prophecies, and shining holiness) that have always been the evident seals of extraordinary divine messengers throughout salvation history? Various Eastern and Greek churches also lack communion with the head of the Church, and therefore the formal element of apostolic continuity, even if they may possess the material aspect of apostolic continuity, such as apostolic foundation, which may be claimed with some validity for some ancient Eastern churches.
All of them have denied the formal principle of apostolicity, the primacy of Saint Peter's successor, which their predecessors still professed; thus, they became different churches. As such (as Eastern Orthodox or Lutheran churches), they were formed centuries after the apostles, and therefore cannot be an apostolic Church. In addition, they explicitly and programmatically separated themselves (especially the Protestants and Eastern Orthodox) from the Roman Church, and therefore deliberately detached themselves from the apostolic body. Since they have formally abandoned the principle and guarantee of apostolicity, it is no wonder that they have also departed from internal apostolicity in principle, especially in apostolic teaching. This is clearly demonstrated by the hesitation of Protestants in the area of teaching, the history of which is the gradual erosion of the Gospel truth down to the denial of Christ. The history of the faith and confession of Eastern churches also provides ample evidence.
On the other hand, the apostolicity of the Catholic Church is self-evident and obvious. The head of the Catholic Church, the Pope, is also the head of the Roman Church, which according to Saint Paul's testimony has an apostolic origin. Moreover, the bishop of Rome, as the head of the Church, is the legal successor of Saint Peter; and the other Catholic church leaders are in legal, doctrinal, and sacramental unity with him; thus, every Catholic church leader is at least an apostolic successor in form. This ensures the apostolic origin and continuity of all, and specifically the apostolicity of teaching. Church history bears witness that the Catholic Church has never compromised apostolic teaching; since the time of the first heresies, it has been its principle not to yield from apostolic tradition. From the very first heretics, the Church confronted them with the Apostolic Creed and the principle of apostolic succession; and it did not waver from this, even if it led to painful sacrifices. The Catholic criterion of apostolicity can be easily and reliably applied. Jesus Christ built his Church on the foundation of St. Peter, the rock; therefore, the true Church of Christ can be found where St. Peter's seat, the rock-foundation, is located. St. Ambrose tells the story of his brother, Satyrus, who, when shipwrecked on an unknown shore, valued the true faith above all else and immediately inquired from the local bishop: is he in unity with the Roman Church? St. Jerome, in the face of Eastern schisms, did the same: "The three-way divided church is tearing me apart. And I cry out: whoever is in unity with St. Peter's seat, that is my man!" St. Augustine calls the Donatists: "Come, brothers, if you want to be grafted into the vine. It pains the human heart to see you cut off like this. Read the bishops, starting from St. Peter's seat, pay close attention to the order of the fathers in which one succeeds the other: this is the rock on which the proud gates of hell shall not prevail." (Ambr. Excess. fratris I 47. Hieron. Epist. 16. August. Ps. c. Donat.)
Proposition: The Church is indefectible. Dogma.
Explanation: The indefectibility of the Church (indefectibilitas) encompasses two aspects: Jesus Christ's Church will endure until the end of time, and this is its constancy, perennitas; moreover, it will remain essentially unchanged in the form that He established, and this is its immutability, immutabilitas. The Church's indefectibility in preserving and proclaiming the revealed truth unchangeably is infallibility. Thus, according to the proposition, the visible Church will always exist on earth; furthermore, the divine element of the Church: the Gospel truth and grace, its instruments: the sacraments and the governing body leading to sanctification, the hierarchy, and its basic organization will always remain the same. However, we should not expect the Church to remain unchanged in incidental matters, such as the Church's fate throughout history, the emergence and disappearance of various non-Christian institutions and movements, the direction of ecclesiastical education, etc. This dogma was denied by those medieval and modern "spiritualists" who expected an eternal Gospel or the age of the Holy Spirit after the age of the Father (Old Testament) and the Son (New Testament), or who proclaimed that after the Petrine (Catholic) and Pauline (Protestant) churches, a Johannine church (without organization and legal character) should follow; such modern sects were the Quakers, Swedenborgians, and Irvingians. Rationalists, including modernists, who drag Christ's Gospel and even more so His Church into the stream of history, also deny the Church's immutability. In opposition to them, the Church has mostly defended the truth expressed in the proposition by condemning erroneous views.
Proof: According to the prophets, the Messiah's kingdom will have no end; God's new covenant, which He makes with humanity, will be eternally valid (2 Samuel 7:12–16; Isaiah 9:6–7, 55:3, 61:8; Jeremiah 31:31–6, 32:40; Daniel 2:44, 7:14; Hosea 2:19; Psalm 71:5–7, 89:36–9; cf. Haggai 2:7, Hebrews 7, 8, Luke 1:32, Hebrews 12:27). The Savior assures that His Church will endure until the end of the world. When sending His disciples out into the world, He assures them, "Behold, I am with you always, to the end of the age." He builds it on the rock foundation so that "the gates of hell" (death, decay; or more likely, the devil's attacks) cannot prevail against it (Matthew 28:20, 16:18; cf. 7:24, John 14:16). Here, the Savior explicitly speaks only of the Church's survival. But implicitly, He also testifies to its unchangeableness; for He always speaks of His Church; but a Church that essentially deviates from His foundation would no longer be His. The apostles proclaim the Church's indefectibility when they call it the body of Jesus Christ, thus considering it a participant in His excellence. The Church is an "eternal covenant", an "unshakable kingdom", the stronghold and pillar of truth; it is meant to save every person, therefore it must exist as long as there are people (1 Cor 12:12, Eph 1:22, 4:13, Col 1:18; Heb 13:20, 1 Cor 11:26; Heb 12:33, 2 Cor 3:11). However, this essential unchangeability is not stagnation and barrenness, but on the contrary: the Church is the mustard seed growing into a mighty tree, the wheat grain sprouting into a stalk, the leaven permeating the body, the Body of Christ maturing toward adulthood (Mt 13, Jn 12:24; Eph 1:23, 4:12, 1 Cor 12:12). The Church is guided and animated by the Word of Christ, which is spirit and life, and gradually leads the called ones into all truth (Jn 6:63, 16, 1 Pet 1:23).
The Church Fathers were deeply convinced that the founding of the Church falls into the fullness of time; it came in the last hour of the world's day, and therefore will remain until the end of this hour, that is, until the end of the world. They justified Christ's presence in the Church as proof that the Church cannot essentially change. "The Lord Christ received the anointing (the anointing of divinity) on his head so that he might breathe incorruptibility into his Church," says St. Ignatius. This conviction speaks powerfully in St. John's speech before his exile: "Do not be discouraged by the Church! For nothing is stronger than the Church. It is higher than the sky, deeper than the earth; it never grows old!" St. Augustine speaks similarly: "No one can erase God's plan from heaven; no one can erase God's Church from the earth." (Ignat. Eph 17, 1; Chrysost. Hom. de captiv. Eutrop. 6; Hom. ante exil. 1 2; August. Epist. 43, 9, 27; in Ps 101, 2, 8; Ambr. in Ps 40, 30; Athanas. in Ps 88, 38.)
The deeper reason for the Church's unchangeability is that in Jesus Christ, God's unshakable wisdom has given the perfect and definitive revelation, which is realized in and through the Church; its sustaining power is God's providential will, which can ensure the existence of the Church until the end of time (Rom 8:31, Eph 5:25), even amidst continuous attacks from opposing historical forces. However, this comforting great truth cannot give grounds for either the members or, especially, the leaders to slacken in apostolic zeal and vigilance; just as the truth of providence in general cannot be a title for rash confidence or inactivity; even less so, because the survival of the whole Church is indeed guaranteed by Christ's promises, but by no means the survival of the Church among individual nations. History confirms the Savior's words that his kingdom is taken away from lazy, unworthy people and careless shepherds, and given to those who produce worthier fruits.
Difficulties. 1. It was prophesied, repeatedly, that the Old Covenant would last forever; yet it gave way to the New Covenant. – Response. The Old Covenant, according to the clear testimony of Scripture, was of a temporary nature. What was intended for eternal preservation in it, Jesus Christ took up into the New Covenant, and thus it continues to live in the New Covenant. Moreover, believing Israel became the seed of the new Church and the heir of Christ's eternal kingdom (Rom 11,1.29.).
2. Everything under heaven changes, and the common fate of human affairs cannot be avoided by Christ's Church. – Response. This extreme relativism has haunted since Heraclitus. However, serious reflection shows that there is unchanging existence, the unconditional reality, God; and therefore, in principle, it is possible and, as a consequence of Christ's promise, certain that the temporal reflection of this unchangeability, the order of revealed truth and grace, the divine element of the Church, will also essentially remain unchanged. Indeed, from a purely philosophical point of view, one can say: If there were no unchanging element in created existence, there could be no change; for change consists in something remaining and something becoming different: quidquid mutatur, quantum ad aliquid manet, quantum ad aliquid transit.
3. According to critics, Church history testifies that the community which primarily calls itself Christ's Church has gone through profound changes. Two impassable chasms cut through the path of church history: one separates Christ from the apostles, the other separates them from the Catholic Church; and even within these two sections, the Church is essentially different around 30, 60, 90, 130, 190 (Harnack). – Response. It can be shown that all the essential elements of the Church, especially its teachings, which are most attacked by liberal Protestants and modernists, originate from Jesus Christ; therefore, the changes are not essential. This is also confirmed in detail by the present dogmatic discussion, which repeatedly points out how far the propositions of the liberal school are not born of history, but of negative dogmatics.