The Church is a visible organization consisting of baptized Christians in local churches under the authority of a bishop from true apostolic succession, in union with the Pope (Gal 1:13, Acts 8:1, Eph 1:15,22, Col 1:18). Jesus even used the term (Matt. 16:18, 18:17). The Magisterium teaches that the Church of the Apostles is one and the same as the Catholic Church today. The Church of the Apostles was called the "catholic church" by Ignatius of Antioch in 110 A.D. (Letter to the Smyrneans, 8:2). However, beginning in the first century, some believers broke away from this Church that Christ established, and formed their own churches (such as the Gnostic and Montanist churches). The original church, the church of the apostles, began calling itself the "Catholic Church" to distinguish it from all the other churches which broke away, claiming the "original church" was no longer the "true church".
That is how one knew which church was the original church. The church that traced the apostolic succession of their local churches back to the apostles, the one that had bishops who descended in an unbroken line beginning with the apostles, was the true church. This made sense, since the truth was to be passed on through a succession of bishops. The apostle Paul handed the truth on to Timothy, a bishop, "the things which you have heard from me," who was to pass it on to succeeding bishops, "hand on to trustworthy men," who were to teach others, and thus continue apostolic succession, "who will be able to teach others" (2 Tim 2:2). Only in the Catholic Church is there an unbroken succession of bishops dating back to the apostles, in union with an unbroken succession of popes (bishops of Rome) dating back to Peter.
Some Protestants complain about the term "Catholic." They say that no one in the Bible is called "Catholic", so the Apostles could not have been Catholics, as Catholics today claim they were. The problem is, until Acts 11:26, no one is called a "Christian." But this does not mean James and Stephen, who died before this, were not Christians. It just means that Christians were not yet given the name, just as the people we read about in the Bible were not yet given the name "Catholic" (they would be given this name later). The Catholic Church is the actual church that the apostles were members of and that Jesus founded.
One of the marks of the True Church is that it be one. In the early Church, we see this unity preserved, especially at the Council of Jerusalem, where the Magisterium of the Church made a decision about Gentile converts that were binding on the entire Church. As Paul said about the unity of the Church: "For it has been reported to me by Chloe's people that there is quarreling among you, my brethren. What I mean is that each one of you says, ‘‘I belong to Paul,' or ‘‘I belong to Apollos,' or ‘‘I belong to Cephas' or ‘‘I belong to Christ.' Is Christ divided? Was Paul crucified for you? Or were you baptized in the name of Paul?" (1 Cor 1:11-13). In Protestantism, we see Christians divided into many denominations, embracing many different beliefs. Only in Catholicism do we see a Church united in doctrine, even though many dissent from these teachings.
Protestants claim that the Christian Church is united––they say that the Church consists of all Christians, and their unity is invisible, rather than corporate. The Catholic Church also teaches this concept, called the Mystical Body of Christ, but the Church also teaches that the Church is a visible organization, consisting of baptized Christians in local churches under the authority of a bishop in union with the pope. Some of the Church's members are invisibly so––those who are justified but are not nominal members of the Catholic Church. The Biblical picture of the Church is Catholic rather than Protestant The Church was to have one and only one faith: "The group of believers was one in mind and heart" (Acts 4:32); "keep the unity of the Spirit . . . there is one body and one spirit . . . one faith" (Eph 4:3-5; 1 Cor. 1:10-13; Phil. 1:27, 2:2, 3:16); "stand fast in one Spirit, with one mind" (Phil 1:27; see also 2:2, 3:16). Denominationalism was condemned: "Where there are . . . divisions among you, are you not carnal and behaving like mere men" (1 Cor 3:3-5); "note those who cause divisions and offenses contrary to the doctrine which you learned [from the bishops and apostles] and avoid them. For those who are such do not serve . . . Jesus Christ" (Rom. 16:17-18); "These are sensual persons, who cause divisions, not having the Spirit" (Jude 19). Jude, earlier in his epistle, makes mention of who these people are. They were described as the people who were following the "rebellion of Korah", who were condemned for rebelling against the priests who were in authority over the People of Israel. So the people who cause divisions and do not have the Spirit are those that rebel against the presbyters and bishops who have authority over the church.
The Church is a "city set on a hill" (Matt. 5:14). Therefore, it must be clearly visible. In Acts 15 we see the elders gathered together for the Council of Jerusalem, in the first Magisterial decision made in the Church. In Matthew 18:15-17, Christ exhorts his followers to take the case of erring brothers "to the Church", which means the Church would have to be visible. Jesus compares the Kingdom of Heaven (which often refers to the Church) with wheat and weeds (Matt. 13:24-30) and good and bad fish (Matt. 13:47-50; Matt. 22:1-14). Therefore, the Church cannot be limited to the elect alone, because some members of the "Kingdom of Heaven" are unregenerate sinners. Yes, Jesus also uses the parable of the shepherd and his sheep (John 10:1-16; 2 Tim. 2:19, 1 John 2:19), but the Bible uses the word sheep to refer to the unsaved as well (Ps. 74:1; 119:176; Ez. 34:2-3,13,23,30; Is. 53:6).
The Bible says that the Church is the "pillar and foundation of the truth" (1 Tim 3:15). The Catholic Church (the church of the New Testament) is the pillar and foundation of the truth because it was given the gift of infallibility, held by the Magisterium––the bishops in union with the pope, who in turn teach laypeople, who must submit to these teachings. A spiritual union of all Christians transcending all denominations cannot be the "pillar and foundation of the truth", because among these Christians, the truth cannot be found, since there is great division regarding doctrine, belief, and practice. Furthermore, with only a fallible interpretation of Scripture, no one can be sure they have the truth.
Protestants may argue that the Catholic Church was at one time the "true church", but is not anymore since it fell into error. However, Jesus said "I am with you always, even to the end of the age" (Matt 28:20), and "the Father . . . will give you another Helper (the Holy Spirit), that He may abide with you forever" (John 14:16). The Church was given the Spirit of Truth (John 14:26, 15:26, 16:13). Christ promised He (Matt 28:20) and the Holy Spirit (Jn 14:16) would be with the Church forever. This means the Church would always teach infallibly (Jn 14:17, 15:26, 16:13). The Spiritual gift of infallibility was passed down through a succession of bishops (1 Tim 4:14). Furthermore, those who began to believe and teach things contrary to the bishops and presbyters were condemned. There is no indication that they were justified in forming another denomination. They were in fact considered to be no longer a member of the church: "having faith . . . which some have rejected, of whom are Hymenaeus and Alexander, whom I have delivered to Satan (excommunicated)" (1 Tim 1:18-20). They were thrown out of the church because they were openly professing a false doctrine. They were saying "the resurrection of the body had already taken place" (2 Tim 2:17). This had nothing to do with the Trinity or sola fide or sola scriptura. It was a belief that would be considered "secondary" according to Protestants. But primary or secondary, denying doctrine was heresy: "warn a heretic once, and then a second time, after that have nothing to do with him . . . such a person . . . stands self-condemned". (Tit 3:10-11; 2 Thess 3:14). This paints the picture of one church, with bishops and presbyters who rule the church, and which considers any person or group of people who rebel through false teaching and belief to be out of the church.
Ignatius of Antioch (Letter to the Smyrneans 8:2 [A.D. 110]) "Wherever the bishop appears, let the people be there; just as wherever Jesus Christ is, there is the Catholic Church"; (Letter to the Philadelphians 3:3-4:1 [A.D. 110]) "If anyone follows a maker of schism, he does not inherit the kingdom of God."
Irenaeus (Against Heresies, 3:4:1 [A.D. 185]) "The truth is to be found nowhere else but in the Catholic Church, the sole deposit of apostolic doctrine. Heresies are of recent formation, and cannot trace their origin back to the apostles"; "The Tradition of the apostles...can be seen in every church by those who with to behold the truth. We can enumerate those who were established by the apostles, and their successors down to our time, none who taught or thought anything like their (the heretics) mad ideas" (ibid. 3:3:1).
Tertullian (Demurrer Against the Heretics 30 [A.D. 200]) "Where was Marcion, that shipmaster of Pontus, the zealous student of Stoicism? Where was Valentinus, the disciple of Platonism? For it is evident that those men lived not so long ago--in the reign of Antonius for the most part--and that they at first were believers in the doctrine of the Catholic Church, in the church of Rome under the episcopate of the blessed Eleutherius, until on account of their ever restless curiosity, with which they even infected the brethren, they were more than once expelled".
Cyprian of Carthage (The Unity of the Catholic Church 4; 1st edition [A.D. 251]) "On him [Peter] he builds the Church, and to him he gives the command to feed the sheep, and although he assigns a like power to all the apostles, yet he founded a single chair, and he established by his own authority a source and an intrinsic reason for that unity. Indeed, the others were also what Peter was, but a primacy is given to Peter, whereby it is made clear that there is but one Church and one chair. So too, all [twelve apostles] are shepherds, and the flock is shown to be one, fed by all the apostles in single-minded accord. If someone does not hold fast to this unity of Peter, can he imagine that he still holds the faith? If he desert the chair of Peter upon whom the Church was built, can he still be confident that he is in the Church?".
Council of Nicaea I (Appendix to the Creed of Nicaea [A.D. 325]) "Those who call 'God the Son of God changeable and mutable,' these the Catholic Church anathematizes".
Cyril of Jerusalem (Catechetical Lectures 18:23 [A.D. 350]) "[The Church] is called Catholic, then, because it extends over the whole world, from end to end of the earth, and because it teaches universally and infallibly each and every doctrine which must come to the knowledge of men, concerning things visible and invisible, heavenly and earthly, and because it brings every race of men into subjection to godliness, governors and governed, learned and unlearned, and because it universally treats and heals every class of sins, those committed with the soul and those with the body, and it possesses within itself every conceivable form of virtue, in deeds and in words and in the spiritual gifts of every description".
Jerome (Commentary on Titus 3:10-11 [A.D. 386]). "Between heresy and schism there is this difference: that heresy involves perverse doctrine, while schism separates one from the Church on account of disagreement with the bishop."
Augustine (The True Religion 7:12 [A.D. 390]) "We must hold to the Christian religion and to communication in her Church, which is Catholic and which is called Catholic not only by her own members but even by all her enemies. For when heretics or the adherents of schisms talk about her, not among themselves but with strangers, willy-nilly they call her nothing else but Catholic. For they will not be understood unless they distinguish her by this name which the whole world employs in her regard"; (Faith and Creed 10:21 [A.D. 393])."We believe in the holy Church, that is, the Catholic Church; for heretics and schismatics call their own congregations churches. But heretics violate the faith itself by a false opinion about God; schismatics, however, withdraw from fraternal love by hostile separations, although they believe the same things we do. Consequently, neither heretics nor schismatics belong to the Catholic Church; not heretics, because the Church loves God, and not schismatics, because the Church loves neighbor"; (Against the Letter of Mani Called "The Foundation" 4:5 [A.D. 397]) "There are many other things which most properly can keep in [the] bosom [of the Catholic Church]. The unanimity of peoples and nations keeps me here. Her authority, inaugurated in miracles, nourished by hope, augmented by love, and confirmed by her age, keeps me here. The succession of priests, from the very see of the apostle Peter, to whom the Lord, after his resurrection, gave the charge of feeding his sheep [John 21:15––17], up to the present episcopate, keeps me here. And last, the very name Catholic, which, not without reason, belongs to this Church alone, in the face of so many heretics, so much so that, although all heretics want to be called ‘‘Catholic,'' when a stranger inquires where the Catholic Church meets, none of the heretics would dare to point out his own basilica or house".
The Catholic Church they all write about is one and the same church, characterized by a succession of bishops beginning with the Apostles, in union with the Pope, the Bishop of Rome and successor of Peter. The church of the Apostles was the same as the church of Augustine, which is the same as the Roman Catholic Church of today. Notice that some of the fathers said that schismatics were not members of the Catholic Church. Schismatics accepted all the doctrines of the Church, but had separated from it. If Protestants were correct––if the "catholic church" was nothing more than true believers, then schismatics would be true believers, since they believed everything that the Christians believed. But the Catholic Church was a visible organization, and as such, to separate from it was to no longer be a member of the Catholic Church. Tertullian's challenge to the heretics of his day remains a challenge to the anti-Catholic Protestants of our day: "If there be any which are bold enough to plant [their origin] in the midst of the apostolic age, that they may thereby seem to have been handed down by the apostles, because they existed in the time of the apostles, we can say: Let them produce the origin of their church; let them display the succession of their bishops, to see if the first was ordained by an Apostle" (Demurrer Against the Heretics 32 [A.D. 200]). After listing the bishops of Rome, beginning with Peter, he writes, "let us see if the heretics can pretend to something like this."