The Bishop of Rome is the bishop of the Holy See, more often referred to in the Catholic tradition as the Pope. The first Bishop of Rome to bear the title of "Pope" was Boniface III in 607, the first to assume the title of "Universal Bishop" by decree of Emperor Phocas. Earlier Bishops of Rome are customarily extended the title Pope as a courtesy, except in strict historical discourse. The title "Bishop of Rome" is also used in preference to Pope by some members of Eastern Orthodox, Anglican, and Protestant denominations, to reflect their rejection of papal authority over the Christian Church.
The Catholic Church holds that the Bishop of Rome is the sole successor to the "supremacy" or primacy of Simon Peter and is thus the "Vicar of Christ" for the world as a whole; however, the Eastern and Oriental Orthodox have no such tradition, but rather view the primacy as a primacy of honor, but not of universal jurisdiction. Protestant Christians likewise reject papal claims of universal jurisdiction.
Early Bishops of Rome were designated Vicar (representative) of Peter; the more authoritative Vicar of Christ was substituted for the first time by the Roman Synod of 495 to refer to Pope Gelasius I, an originator of the doctrine of papal supremacy—Petrine supremacy among Catholics— among the patriarchs. The exclusivity of Rome's claim to Petrine authority has often been questioned. Saint Cyril of Alexandria refers to the See of Antioch as the "See of Peter," thus suggesting the Antiochene Patriarch had a claim to Petrine authority.
The Roman Catholic view is founded on the verses in Matthew 16:18 and John 21:15-19 Roman Catholic dogma claims that a special authority was given by Christ to Saint Peter in these verses and that this special authority was bequeathed to the Bishop of Rome. In opposition to these claims, many non-Roman Catholic Christians point to other verses of Scripture such as Matthew 16:21-23; Luke 22:31-33; and Galatians 2:7-14 They point out that Peter was not always protected from fallibility in matters of faith and that the keys given to Peter were likewise granted to all the apostles in Matthew 18:18
With the title "Vicar of Christ," the Pope claims jurisdiction over the entire Christian Church and supreme authority over all matters of faith and morals. Modern Catholic doctrine concerning the Pope was authoritatively declared in the First Vatican Council (1870) in the Constitution "Pastor Aeternus". The doctrine of papal infallibility espoused at the First Vatican Council was rejected by such noteworthy Roman Catholics as Johann Joseph Ignaz von Döllinger.
By definition, all non-Roman Catholic Christians reject the Papal title of "Supreme Head of the Church" or any title that gives him universal ecclesiastical authority. This holds true especially for the Oriental Orthodox Church, the Eastern Orthodox Church, and all Protestants. Some Assyrian, Eastern Orthodox, and Oriental Orthodox Churches accepted governance by the Roman Pontiff in recent centuries due to missionary endeavors, sometimes involving "Holy Inquisition." These churches are referred to as Uniate by the Orthodox churches which continue to reject the supremacy of any one bishop.