Christianity shifted its center from Jerusalem to Rome around A.D. 70, when the Romans suppressed a Jewish rebellion and destroyed Jerusalem. Peter, proclaimed by Jesus to be the rock of the Church, had worked and died in Rome. He left behind a line of apostolic succession of bishops (or popes) who would maintain the Roman bishopric as the spiritual center of the Catholic Church.

As the Church continued to grow, a number of strong, forceful characters helped shape its development. Whether they were bishops or laypeople with a strong religious bent, the Church would not be what it is today without them.

Clement of Rome

Clement became the third Bishop of Rome around the end of the first century. Some evidence — though no proof — suggests that he worshiped with Peter and Paul. If so, he was very close to the source of divine inspiration, and its influence on him would have been great.

Clement's fame comes mainly from one masterful letter in which he establishes the inviolable authority and primacy of the Church of Rome, which descends from Peter through apostolic succession. Clement wrote his letter to the church of the Corinthians, who had been led into sedition, and he demanded their return to obedience.

Here is what a peer of his time, a man named Eusebius, wrote of him in his Ecclesiastical History: “Clement has left us one recognized epistle, long and wonderful, which he composed in the name of the Church of Rome. In many churches this epistle was read aloud to the assembled worshipers in early days, as it is in our own.”

Clement may have suffered a martyr's death. According to a story that surfaced in the fourth century, the Emperor Trajan was miffed that Clement had converted so many pagans to Christianity and banished him to a quarry, where he performed a miracle and slaked the thirst of thousands. Trajan then ordered Clement to be weighted down with an iron anchor and tossed into the sea near Crimea. When the waves subsided, Clement was entombed in marble by angels.

Ignatius of Antioch

Ignatius, the third bishop of Antioch, lived from the first to second centuries. He was a good pastor and gave his people courage when the Emperor Domitian began persecuting Christians.

Ignatius was a strong and impassioned writer. He sent epistles to various churches — to the Ephesians, Magnesians, Trallians, Romans, Philadelphians, Smyrnaeans, and to Polycarp. In his letters, Ignatius warns against heresies and explains that they are a threat to unity.

He continued to write while under arrest and on his way to Rome. Ignatius of Antioch was sentenced to be torn apart by lions at the Flavian amphitheater in Rome. He died a martyr.

Irenaeus of Lyon

Irenaeus grew up in Smyrna, where he remembered hearing the great bishop Polycarp, another father of the Church, talk about the apostle John. Irenaeus was ordained in Lyon. There, he witnessed the horrifying martyrdom of Greek-speaking Christians, including Lyon's bishop. Irenaeus traveled to Rome to tell the bishop, who asked Irenaeus to return to Lyon, take over the duties of the martyred bishop, and help rebuild the Christian Church. (By “Church,” the pope meant the Christian community, not a physical building.)

In his writings, Irenaeus argued against the Gnostics, who did not accept the humanity of Jesus Christ because they saw the body as evil. Irenaeus also fought for and helped perpetuate the idea of apostolic succession.

Clement of Alexandria

Clement of Alexandria was a second-century teacher who traveled among the Greek-speaking communities before settling in Alexandria to start a school. He is known for three important philosophical works expressing his ideas: The Protrepticus, The Paedogogus (“The Tutor”), and The Stromateis. One of his ardent beliefs was that a Christian life should be devoted to the perfect knowledge of truth.