This doctrine is similar to certain secular views of inerrant procedural safeguards in the law, such that a jury verdict combined with other procedural protections can reduce the possibility of error to zero.
Papal infallibility was established during the First Vatican Council in 1871. At the time, Italy was being formed and the Catholic Church was losing its political status in the world. The Church wanted to clarify its authority with regard to these events. It was the favored idea of Pope Pius IX, (reigned 1846-78), supported by around 50 devoted bishops and the Jesuits. Most of the opposition came from the 88 French bishops in attendance. The majority (45) supported the Pope but a minority of 25 held to both a Gallican, and in some cases a 'modernist,' line. Eventually the minority fell in line and the ultramontane position of the Pope was completely dominant inside the Catholic Church.
Conditions for Infallibility
In order for a teaching by the Pope to be infallible, certain conditions must be fulfilled:
"...when the Roman Pontiff speaks ex cathedra, that is, when, in the exercise of his office as shepherd and teacher of all Christians, in virtue of his supreme apostolic authority, he defines a doctrine concerning faith or morals to be held by the whole Church, he possesses, by the divine assistance promised to him in blessed Peter, that infallibility which the divine Redeemer willed his Church to enjoy in defining doctrine concerning faith or morals, and that therefore such definitions of the Roman pontiff are of themselves and not from the consent of the Church irreformable."
To break down the four different conditions set out here, the Pope must...:
- ...be teaching "ex cathedra" as the head and shepherd of the Church.
- ...explicitly make it clear that he "defines" the teaching, such as through a specific phrase or formula. ("...we pronounce, declare, and define...")
- ...be teaching on a question of "faith and morals", as opposed to e.g. a question of canon law.
- ...and it must be a teaching "to be held by the whole Church", such as expressed through a declaration of excommunication on those who refuse the teaching. ("Hence if anyone, which God forbid, should dare willfully to deny or to call into doubt that which we have defined, let him know that he has fallen away completely from the divine and Catholic Faith.")
In the language of the Catholic Church, these conditions are very specific, and only a few papal teachings are actually considered infallible.
Current Infallible Teachings
Since the First Vatican Council, only two infallible teachings have been made:
- Immaculate Conception (the dogma that Mary was born without original sin) - Declared infallible in 1854 by Pius IX
- Assumption (the dogma that after Mary's death, her body was physically raised into heaven) - Declared infallible 1950 by Pius XII
In 1994, there were concerns that a letter opposing female ordination may have been an infallible teaching according to this criteria. However, Benedict XVI (then known as Cardinal Ratzinger) has rejected these claims.
Certain other historical teachings by past Popes are similarly considered infallible.
In spite of these conditions, papal infallibility is often misunderstood by the general public, who think that it means the Pope is always free of error, or that he is even free of sin, neither of which are actually the case.
Roman Catholic Opposition
Johann Döllinger (1799-1890) was a leading German Catholic theologian and professor at the University of Munich. He rejected the doctrine of papal infallibility, warning it would permanently alienate the Catholic Church from 'all thinking men'. He was excommunicated by Rome and but refused to become the bishop of the breakaway "Old Catholic Church."
Additional voices of past opposition are compiled in such works such as Roman Catholic opposition to papal infallibility
In 1970 Roman Catholic liberal theologian Hans Kung (March 19, 1928) wrote Infallible? An inquiry, which argued that historically papal infallibility was not always universally accepted in the Roman church, with the position that bishops were direct successors to the Apostles also being seen as contrary to history. In December 18, 1979, the controversial theologian was stripped of his missio canonica, the authority by virtue of which he instructs future priests in fundamental theology, it being decided that “Professor Küng may no longer teach theology and may no longer be considered to be a Catholic theologian."
British Prime Minister William E. Gladstone denounced the dogma of papal infallibility as a threat to the civil allegiance of Roman Catholics. His 'Expostulation' sparked a brief but intense controversy, notable for the personalities involved, such as Cardinals Newman and Manning and Lord Acton. While Catholics replied to Gladstone, he received almost no Protestant support. The controversy provided the last occasion for anti-Catholic agitation in England and marked the demise of anti-Catholicism as an overt political issue.
The doctrine of papal infallibility has often been a principal subject of American Protestants opposing the Catholic Church. Various arguments are articulated, with proof texts for papal infallibility being contended against.  
- Dulles, Avery Cardinal. Magisterium: Teacher and Guardian of the Faith (2007), by leading Catholic theologian
- Hasler, August Bernard. How the Pope Became Infallible: Pius IX and the Politics of Persuasion (1980), popular history.
- Hales, E. E. Y. Pio Nono: A Study in European Politics and Religion in the Nineteenth Century (1954) online edition
- O'Connor, James T. The Gift of Infallibility: The Official Relatio on Infallibility of Bishop Vincent Ferrer Gasser at Vatican Council I (2nd ed. 2008), pro. excerpt and text search
- Ott, Michael. "Pope Pius IX" in The Catholic Encyclopedia. Vol. 12. (1911) online
- Powell, Mark E. Papal Infallibility: A Protestant Evaluation of an Ecumenical Issue (2009) excerpt and text search
- Tierney, Brian. Origins of Papal Infallibility 1150-1350; a Study on the Concepts of Infallibility, Sovereignty and Tradition in the Middle Ages (1972), the dogma was invented in the Middle Ages
- Toner, Patrick. "Infallibility." in The Catholic Encyclopedia. Vol. 7. (1910) online
- online books and articles from Questia
- Margaret O'Gara, Triumph in Defeat: Infallibility, Vatican I, and the French Minority Bishops (1988)
- First Vatican Council, Session 4: First Dogmatic Constitution on the Church of Christ, chapter 4, paragraph 9
- Apostolic Constitution Munificentissimus Deus Defining the Dogma of the Assumption, paragraph 44
- Ibid., par. 45
- W. J. Sparrow Simpson, Roman Catholic opposition to papal infallibility, 1909
- The Universe, The Pope Silences Dr. Küng, December 21, 1979
- Josef L. Altholz, "The Vatican Decrees Controversy, 1874-1875," Catholic Historical Review 1972 57(4): 593-605
- John Harvey Treat, Johann Augustus Bolles, G. H. Houghton Butler, The Catholic faith, or, Doctrines of the Church of Rome contrary to scripture and the primitive church, pp. 480ff
- What Think Ye of Rome? Part Four: The Catholic-Protestant Debate on Papal Infallibility, Christian Research Journal, Fall 1994, page 24
- White, A Response to David Palm's Article on Oral Tradition from This Rock Magazine, May, 1995
- A Response to an Argument for Infallibility
- White, Of Athanasius and Infallibility
- White, Exegetica: Roman Catholic Apologists Practice Eisegesis in Scripture and Patristics
- E.J.V. Huiginn, From Rome to Protestantism", The Forum, Volume 5, p. 111
- Peter De Rosa, Vicars of Christ: the Dark Side of the Papacy
- Harold O. J. Brown, Protest of a Troubled Protestant, New Rochelle, NY: Arlington House, 1969; p. 122
- Williston Walker, A History of the Christian Church, 3d ed. New York: Charles Scribner’s Sons, 1970; p. 67
- E.J.V. Huiginn, From Rome to Protestantism", The Forum, Volume 5, pp. 109-110