The papacy is the oldest continuously functioning office in Western Christianity. Catholic tradition holds that Jesus Christ commissioned the apostle Peter as the rock on which the Church would be built, and that Peter served as first Bishop of Rome before his martyrdom under Nero in the first century. Historians trace the office's development more cautiously: the bishops of Rome held no unchallenged primacy in the earliest centuries, and papal authority grew alongside Rome's prestige as the empire's former capital, the presence of Peter and Paul's traditional tombs, and the city's role as a court of appeal in doctrinal disputes.
Papal authority today rests on the doctrine of Petrine primacy, formalized most explicitly at the First Vatican Council in 1870, which defined papal infallibility for solemn pronouncements on faith and morals made ex cathedra, a power exercised only rarely. As Bishop of Rome, the Pope governs the worldwide Roman Catholic Church through the Roman Curia, appoints bishops, calls and confirms the decrees of ecumenical councils, and serves as a visible symbol of the Church's unity. The office also carries civil sovereignty over Vatican City State, an arrangement dating to the 1929 Lateran Treaty that resolved the Roman Question left by the loss of the Papal States in 1870.
The papacy's authority has never gone unchallenged. Eastern Orthodoxy rejects universal papal jurisdiction while honoring Rome's historic place of honor; the Reformation rejected papal authority outright; and within Catholicism itself, councils and popes have at times disputed where final authority lies, most sharply during the fourteenth-century Western Schism, when rival claimants divided the Church.