Without question, St. Peter was the first pope of the Catholic Church. Since the church was under persecution by the Roman Empire until A.D. 313 and the official Roman historians were not concerned with the affairs of the church, we must rely on the testimony of the early church fathers.
St. Irenaeus (d. 202) in his Adversus Haereses described how the church at Rome was founded by St. Peter and St. Paul and traced the handing on of the office of St. Peter through Linus, Cletus (also called Anacletus), Clement and so on through 12 successors to his own present day, Pope Eleutherius. (Even in the Roman Canon, or the first eucharistic prayer, we remember St. Peter and the apostles, as well as Linus, Cletus and Clement, these first four popes of the church who reigned during the first century.) Moreover, St. Irenaeus emphasized the teaching authority of the pope: “For with this church (of Rome), because of its superior origin, all churches must agree, that is, all of the faithful in the whole world; and it is in her that the faithful everywhere have maintained the apostolic tradition.” Here the office of the pope was recognized as instituted by Christ to provide leadership and authentic teaching for the whole church.
St. Irenaeus also highlighted the problems that arose in the church of Corinth during the time of Pope Clement and how he intervened on his own initiative to take corrective action: “In the time of this Clement, no small dissension having occurred among the brethren at Corinth, the church in Rome dispatched a most powerful letter to the Corinthians, exhorting them to peace, renewing their faith, and declaring the tradition which it had lately received from the apostles.” The beauty of this incident is that the church in Corinth respected the authority of the successor of St. Peter, repented and made appropriate corrections. Moreover, St. Eusebius (d. 339) noted in his History of the Church how this letter was received, read and respected in other churches: “Clement has left us one recognized epistle, long and wonderful, which he composed in the name of the church at Rome and sent to the church of Corinth, where dissension had recently occurred. I have evidence that in many churches this epistle was read aloud to the assembled worshipers in early days, as it is in our own.” Clearly, the church as a whole recognized the primacy and authority of the successor of St. Peter.
Another great early church father to highlight is St. Cyprian of Carthage (d. 258). In his The Unity of the Catholic Church, he taught, after citing Matthew 16:13-20: “And again (Jesus) says to (Peter) after His resurrection: ‘Feed my sheep.’ On him 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. … A primacy is given to Peter, whereby it is made clear that there is but one church and one chair. So too, all are shepherds, and the flock is shown to be 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 deserts the chair of Peter upon whom the church was built, can he still be confident that he is in the church?” Remember that the chair represents the office and the authority of the pope which Jesus gave to St. Peter and his successors. Here again the office of the pope was recognized as instituted by Christ to be a sign of unity and to provide leadership and authentic teaching for the whole church.
Many other early church fathers during the times of persecution, like Tertullian (d. 250) in De praescriptione haereticorum and Origen (d. 254) in his Commentaries on John, also attest to the office, role and authority of St. Peter and his successors. Of course, these attributes become magnified after the legalization of Christianity, and especially after the fall of the Roman Empire and the ensuing political chaos. Nevertheless, our church boasts of an unbroken line of legitimate successors of St. Peter who stand in the stead of Christ as His vicar, and are a fundamental source of church unity.
For good reason, the Second Vatican Council noted that the pope, the bishop of Rome and the successor of St. Peter, “is the perpetual and visible source and foundation of the unity both of the bishops and of the whole company of the faithful. For the Roman pontiff, by reason of his office as vicar of Christ and as pastor of the entire church, has full, supreme, and universal power over the whole church, a power which he can always exercise unhindered” (“Lumen Gentium,” No. 22, 23). Nevertheless, we must always remember that one of the official titles of the pope, first taken by Pope Gregory the Great (d. 604), is “servant of the servants of God.” As we think of this answer, may we be mindful of our Holy Father, Pope Benedict XVI, and pray for his intentions.