After the martyrdom of Saints Peter, St. Linus was appointed Bishop of Rome, and after eleven years, succeeded by St. Cletus. Upon his demise in 91, St. Clement was placed in the apostolic chair. According to the Liberian Calendar, he sat nine years, eleven months, and twenty days. Pope Saint Linus was the second Bishop of Rome and Supreme Pontiff of the Catholic Church. His pontificate endured from circa AD 67 to his death. Among those to have been Pope, Saint Peter, Linus, and Clement are specifically named in the New Testament.
The Fathers of the Church spread the gospel of Jesus Christ, defended the Church in apologetic writing and fought the many heresies of the first six centuries of Christianity. These men, also called Apostolic Fathers, gave special witness to the faith, some dying the death of a martyr. Like Jesus who referred to Abraham as a spiritual father (Luke 16: 24) and St. Paul, who referred to himself in the same terms (1 Cor 4: 15), the Fathers were zealous for the word of God. Their writings are a testimony to the faith of the early Church, yet many Christians are unfamiliar with the work of Clement of Rome, Ignatius of Antioch, Polycarp of Smyrna, Justin the Martyr, Irenaeus, Tertullian, Origen, Cyprian of Carthage, Athanasius, Ephraim, Cyril of Jerusalem, Hilary of Poitiers or Gregory the Great to name of few of the early Fathers.