The word pope means father. In ancient Greek it was a child’s term of affection for the father of the family, but was borrowed by later Latin as an honorific. Both Greek-speaking Eastern and Latin-speaking Western Catholics then applied it to priests, bishops and patriarchs as heads of their spiritual families. Today, priests of the Orthodox Churches of Greece, Russia and Serbia still call their parish priest pope.

Gradually, however, Latin Christianity began to restrict its usage. At the beginning of the 3rd century, papa was a term of respect for clergy in high positions. By the 5th century, it was applied particularly to the Bishop of Rome, without excluding other usages. After the 8th century, however, as far the West was concerned the title was exclusively used of the Bishop of Rome. Indeed, the great reforming Pope, Gregory VII (1073-1085), officially restricted its use to the Bishop of Rome.

As the Council of Florence affirmed in 1439, defined as a matter of faith by the First Vatican Council in 1870, and endorsed by the Second Vatican Council in 1964, Jesus Christ conferred the position of primacy in the church upon Peter alone. In solemnly defining the Petrine primacy, the First Vatican Council cited the three classical New Testament texts long associated with it: John 1:42, John 21:15 ff., and, above all, Matthew 16:18 ff. The council understood these texts, along with Luke 22:32, to signify that Christ himself constituted Saint Peter as prince of the apostles and visible head of the church, possessed of a primacy of jurisdiction that was to pass down in perpetuity to his papal successors, along with the authority to pronounce infallibly on matters of faith or morals.

The importance of Peter in the Church Christ established is also affirmed by the more numerous mentions of this apostle in the New Testament and the evident authority of Peter on those occasions. At the Council of Jerusalem (Acts 15), it was Peter who decided what was to be done with Gentile converts and states that choice as a matter of firm policy. Indeed, it was to Peter that God revealed that the gentiles were to be evangelized, even though it would be Paul who would become their most-fervent apostle.