Papal Infallibility

Papal infallibility is the gift by which the pope, when he solemnly defines a doctrine of faith or morals to be held by the whole Church, is preserved from error by the assistance of the Holy Spirit. This gift bears on his solemn teaching, and is exercised under precise conditions.

The promise made to Peter

Christ built his Church on Peter and entrusted to him the keeping of the faith. He says to him: “You are Peter, and on this rock I will build my Church, and the gates of hell shall not prevail against it.” Matthew 16:18 And on the eve of his Passion: “I have prayed for you, that your faith may not fail; and when you have turned again, strengthen your brothers.” Luke 22:32 The Lord himself prays that Peter's faith may hold, and gives him to strengthen the others. Infallibility prolongs this prayer of Christ over the successor of Peter.

The conditions of the infallible act

The pope engages this gift only when four conditions are met. He speaks as supreme pastor and teacher of all Christians; he uses his supreme apostolic authority; he defines a doctrine of faith or morals; he declares it to be held by the whole Church. Such an act is called a definition ex cathedra, “from the chair” of Peter. Outside these conditions, in his homilies, his interviews, his decisions of governance or his personal opinions, the pope teaches and deserves respect, without being covered by this gift.

The keeping of the deposit

The gift preserves from error by keeping the deposit received. The pope keeps the faith handed down from the Apostles and sets it forth faithfully; the Spirit prevents him from leading the Church astray at the moment he fixes what she must believe. Revelation was completed with the Apostles, and infallibility serves its faithful transmission, not the adding of a new word.

The infallibility of the Church

This gift of the pope flows from a promise made to the whole Church. Christ assured her against error, “the gates of hell shall not prevail against it” Matthew 16:18, and he gave her his Spirit: “the Spirit of truth will guide you into all the truth.” John 16:13 The Church therefore cannot fail in the faith. The pope exercises at given moments this infallibility that belongs to the whole body, to settle matters when the unity of the faith is at stake and to keep all the faithful in one same truth.

The pope remains a man

Infallibility bears on the defined teaching, and leaves the human condition of the pope intact. He can sin, err in his judgments, fail in his conduct; history has known popes both holy and unworthy. The gift makes him neither holy nor omniscient. It keeps his solemn word from error, so that the flock entrusted to Peter may never be taught what is false.

Its definition at the council

The Church lived this assurance from the beginning; she defined it in proper terms at the First Vatican Council, in 1870. Its solemn exercise remains rare. Two Marian proclamations illustrate it: the Immaculate Conception, declared by Pius IX in 1854, and the Assumption, declared by Pius XII in 1950. In more than twenty centuries, the pope has spoken thus only to fix what touches the heart of the faith.