In my humble opinion, as a former Lutheran, to be a Christian is to be a Catholic, because the unity the bible speaks of so often can be found exclusively in the C.C. *IT ONLY TOOK 20 YEARS TO FIGURE THAT OUT.
Christ revealed the truth and gave it to His Church, and men are to be saved by knowing and following the truth. But the essential unity of the true Christian Church is also explicitly and repeatedly declared throughout the New Testament:
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* Speaking of His Church, the Saviour called it a kingdom, the kingdom of heaven, the kingdom of God (Matthew 13:24, 31, 33; Luke 13:18; John 18:36);
* He compared it to a city the keys of which were entrusted to the Apostles (Matthew 5:14; 16:19),
* to a sheepfold to which all His sheep must come and be united under one shepherd (John 10:7-17);
* to a vine and its branches,
* to a house built upon a rock against which not even the powers of hell should ever prevail (Matthew 16:18).
* Moreover, the Saviour, just before He suffered, prayed for His disciples, for those who were afterwards to believe in Him -- for His Church -- that they might be one and remain one as He and the Father are one (John 17:20-23); and
* He had already warned them that "every kingdom divided against itself shall be made desolate: and every city or house divided against itself shall not stand" (Matthew 12:25).
These words of Christ are expressive of the closest unity.
St. Paul likewise insists on the unity of the Church.
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* Schism and disunion he brands as crimes to be classed with murder and debauchery, and declares that those guilty of "dissensions" and "sects" shall not obtain the kingdom of God (Galatians 5:20-21).
* Hearing of the schisms among the Corinthians, he asked impatiently: "Is Christ divided? Was Paul then crucified for you? or were you baptized in the name of Paul?" (1 Corinthians 1:13).
* And in the same Epistle he describes the Church as one body with many members distinct among themselves, but one with Christ their head: "For in one Spirit we are all baptized into one body, whether Jews or Gentiles, whether bond or free" (1 Corinthians 12:13).
* To show the intimate union of the members of the Church with the one God, he asks: "The chalice of benediction, which we bless, is it not the communion of the blood of Christ? And the bread, which we break, is it not the partaking of the body of the Lord? For we, being many, are one bread, one body, all that partake of one bread" (1 Corinthians 10:16-17).
* Again in his Epistle to the Ephesians he teaches the same doctrine, and exhorts them to be "careful to keep the unity of the Spirit in the bond of peace", and he reminds them that there is but "one body and one spirit-one Lord, one faith, one baptism, one God and Father of all" (Ephesians 4:3-6).
* Already, in one of his very first Epistles, he had warned the faithful of Galatia that if anybody, even an angel from heaven, should preach unto them any other Gospel than that which he had preached, "let him be anathema" (Galatians 1:8).
Such declarations as these coming from the great Apostle are clear evidence of the essential unity which must be characteristic of the true Christian Church.
The other Apostles also persistently proclaimed this essential and necessary unity of Christ’s Church (cf. 1 John 4:1-7; Apocalypse 2:6, 14-15, 20-29; 2 Peter 2:1-19; Jude 5:19). And although divisions did arise now and then in the early Church, they were speedily put down and the disturbers rejected, so that even from the beginning the Christians could boast that they were of “one heart and one soul” (Acts 4:32; cf. Acts 11:22; 13:1).
Tradition is unanimous to the same effect. Whenever heresy threatened to invade the Church, the Fathers rose up against it as an essential evil.
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* The unity of the Church was the object of nearly all the exhortations of St. Ignatius of Antioch ("Ad Ephes.", n. 5, 16-17; "Ad Philadelph.", n. 3).
* St. Irenaeus went even further, and taught that the test of the one true Church, in which alone was salvation, was its union with Rome (Adv. haeres., III, iii).
* Tertullian likewise compared the Church to an ark outside of which there is no salvation, and he maintained that only he who embraced every doctrine handed down by the Apostolic Churches, especially by that of Rome, belonged to the true Church (De praescript., xxi).
* The same contention was upheld by Clement of Alexandria and by Origen, who said that outside the one visible Church none could be saved.
* St. Cyprian in his treatise on the unity of the Church says: "God is one, and Christ one, and one the Church of Christ" (De eccl. unitate, xxiii); and again in his epistles he insists that there is but "One Church founded upon Peter by Christ the Lord" (Epist. 70, ad Jan.) and that there is but "one altar and one priesthood" (Epist. 40, v).
Many more testimonies of unity might be adduced from Saints Jerome, Augustine, Chrysostom, and the other Fathers, but their teachings are only too well known. The long list of councils, the history and treatment of heretics and heresies in every century show beyond doubt that unity of doctrine of cult, and of authority, has always been regarded as an essential and visible mark of the true Christian Church. As shown above, it was the intention of Christ that His Church should be one, and that, not in any accidental internal way, but essentially and visibly. Unity is the fundamental mark of the Church, for without it the other marks would have no meaning, since indeed the Church itself could not exist. Unity is the source of strength and organization, as discord and schism are of weakness and confusion. Given one supernatural authority which all respect, a common doctrine which all profess, one form of worship subject to the same authority and expressive of the same teaching, centred in one sacrifice and in the reception of the same sacraments, and the other marks of the Church necessarily follow and are easily understood.
That the mark of unity which is distinctive of and essential to the true Church of Christ is to be found in none other than the Roman Catholic Church, follows naturally from what has been said. All the theories of unity entertained by the sects are woefully out of harmony with the true and proper concept of unity as defined above and as taught by Christ, the Apostles, and all orthodox Tradition. In no other Christian body is there a oneness of faith, of worship, and of discipline. Between no two of the hundreds of nonCatholic sects is there a common bond of union; each one having a different head, a different belief, a different cult. Nay more, even between the members of any one sect there is no such thing as real unity, for their first and foremost principle is that each one is free to believe and do as he wishes. They are constantly breaking up into new sects and subdivisions of sects, showing that they have within themselves the seeds of disunion and disintegration. Divisions and subdivisions have ever been the characteristics of Protestantism. This is certainly a literal fulfilment of the words of Christ: “Every plant which my heavenly Father hath not planted shall be rooted up” (Matthew 15:13); and “every kingdom divided against itself shall be made desolate: and every city or house divided against itself shall not stand” (Matthew 12:25).
