As head of the Roman Catholic Church, the pope is the supreme spiritual leader of the Church and controls the church doctrine. With a billion followers, the pope's decisions impact societies and governments all over the world.
To understand the authority of the papacy, we should first understand a little history of the Roman Catholic Church.
The Catholic Church dates back to the time of Jesus Christ, when Christ selected Peter to lead his Church. In the book of Matthew (16:18) of the Bible, Christ says to Peter, "And I say also unto thee, That thou art Peter, and upon this rock I will build my church; and the gates of hell shall not prevail against it." This statement, now known as the Petrine guarantee, gave Peter the fullness of power, according to the New Catholic Encyclopedia.
Many theologians believe the "rock" of which Christ spoke is Peter himself. Peter's original name was Simon; Christ gave Peter another name, Cephas, an Aramaic word meaning "rock." Aramaic is the language that Christ spoke. Knowing this, Matthew 16:18 can be interpreted as Christ saying that he is building his Church on the strength of Peter. Further evidence of this conferment of power is in John 21:15-19, when Christ tells Peter, "Feed my sheep."
Upon Christ's ascension, Peter became the undisputed leader of the Church based on the powers given from Christ to Peter. At some point in his life, likely at the end of his life, Peter moved to Rome to spread the word of Christ, according to the New Catholic Encyclopedia. It was in Rome where Nero, the Roman emperor who persecuted the church, killed Peter. Through his death, Peter became a martyr. His body was buried on Vatican Hill. St. Peter's Cathedral was later erected over his grave.
During his life, Peter was never officially the bishop of Rome or the pope, but in honor of his work and his role as the head of the Church, he is recognized as the first pope. Every pope since Peter is considered the immediate successor of Peter, and not of that pope's immediate predecessor. A pope is considered to be carrying on the power that Christ granted Peter. Today, a great amount of the pope's powers are derived from the Petrine guarantee, which is etched in Latin around the perimeter of dome of St. Peter's Cathedral.
The pope's powers were bolstered in the First Vatican Council in 1870, when 433 bishops passed the decree of papal infallibility. This decree declared that the pope was infallible in matters of faith and morality. According to the decree, the pope "is possessed of that infallibility with which the Divine Redeemer wished His Church to be endowed."
The next two sections explain the process of papal succession.