After the death and resurrection of Jesus, his disciples began travelling and spreading his message. At first they held with all the Jewish traditions and spread the word among their own people. With the conversion of Paul (Saul), who worked for the Roman govornment hunting down Christians and bringing them to trial, the "major doctrine" was developed. Paul said that ANY who believed and were Baptized could recieve salvation. Paul also added the theological point that Christians were the "true Israel", an Israel of faith rather than one of flesh (the Jews).
From the beginning, the leaders of the Christian faith (the apostles) agreed that only those they taught directly could teach others about the truths of this new religion. Each apostle specified a special student to take his place when he died. This student, in turn, taught others, and selected one to carry on for him when he died. This is called the Apostolic Line.
In the modern Catholic church, it is recognized that Peter was the chosen of Jesus to continue his ministry. According to the Scriptures, Matthew 16:13- 19, Christ said to Peter: "And I tell you, you are Peter, and on this rock I will build my church." Each of the others was recognized as the equivalent of what we know of as Bishops in the Apostolic Line. The Pope is supposedly the direct heir to Peter. The Christian faith was not established in Rome until 380, after persecution was outlawed by Constantine in 313.
It's important to note that no matter what branch you are talking about of the Catholic Church, they all universally recognize that each has an unbroken Apostolic Line. Different denominations are called Rites, Catholic being a universal term to encompass them all. This includes Roman Rite, Anglican Rite, Celtic Rite, Orthodox Rite (Eastern or Western) and Gallican Rite. All are valid expressions of the Orthodoxy of the one, holy, catholic and apostolic Church (as considered by the Independent Catholic Union).
Personally, I'm Baptist, but one of my ex-wives was Catholic and I spent many a pleasant evening arguing with her Priest. Drunken bastige that he was.
