The term pope was originally used for all of the many bishops of the western leg of the Roman church. Although the Vatican's official list of popes now begins in the first century AD, in reality it was about 400 years later that the term was used exclusively for the bishop of Rome i.e. from only about 500 AD did that particular bishop begin to assume authority over the entire Church of Rome. The "primacy of the bishop of Rome" doctrine was hotly contested among Catholics for centuries.
The office of the bishop of Rome was itself often challenged. In the history of the Roman Church, the term antipope is used for a man who usurped or contended for the position of bishop of Rome, and who succeeded, to some degree, for some length of time. There were periods in the history of the Roman papacy that two, and sometimes three, men claimed to be the pope at the same time, each with a substantial religious and political following.
Antipopes came to power under diverse circumstances. Some examples:
- Political Exile
When the Arian-believing emperor Constantius II found the orthodox beliefs of Pope Liberius unacceptable, the emperor installed an archdeacon as Pope Felix II (355-365).
- Doctrinal Challenge
The growth of Monarchianism caused a priest, Hippolytus (217-235), to claim the papacy against Pope Calixtus I.
- Double Elections
In 418, competing camps elected their own popes, Eulalius, an archdeacon, and Boniface I, a priest.
- Triple Elections
In the 7th century, both Paschal and Theodore were elected pope by their respective supporters. When neither of them could gain the upper hand for control over the other, Sergius I was elected pope by another group.
- Election Changes
In 1059 a change was instituted in the way popes were elected. Pope Nicholas decreed that the German emperors would no longer have a leading role in the selection of popes. This resulted in 2 popes being elected, one by the old rules, one by the new: Honorius II and Alexander II.
- The Great Western Schism
In the 14th century the papal residence was moved to Avignon, France. This resulted in 3 elected popes at the same time: a papacy in Rome, a papacy in Avignon, and later a third papacy in Pisa.
Fact Finder: What was the papacy's role in the political history of Europe?
See Emperors and Popes