Infallibility, the immunity from error, in all that regards faith and morals, which is claimed by the Roman Catholic Church, and, at least as regards the past, by the Greek Church, as represented in the decrees of the councils which that church looks upon as ecumenical. The latter claim, however, which does not go beyond that of inerrancy, or actual exemption from error up to the present time, differs widely from that of infallibility, as put forward by the Roman Church, which involves not alone an actual historical immunity from error, but also such a positive and abiding assistance of the Spirit of God as will at all times both protect against the possibility of error and guide and direct in the faithful teaching of all necessary truth. The infallibility claimed by the Roman Church is thus of two kinds, passive and active—the first (Matt. xvi. 18), in virtue of which the church never can receive or embrace any erroneous doctrine, no matter by whom proposed; the second, in virtue of which she is charged with the function (Matt. xxviii. 19; Mark, xvi. 15; Ephes. iv. 11-16) of permanently teaching to the world the essential truths of God, of actively resisting every access of error, and of authoritatively deciding every controversy by which the oneness of belief among the faithful may be endangered. Catholics regard this gift as a natural and necessary accompaniment of the authority in matters of faith with which they believe the church to be invested, and which, if not guided in its exercise by such infallible assistance, would be but a false light and an attractive but dangerous instrument of delusion.
Such is the notion of infallibility as claimed by the Roman Church. Two very important and practical questions, however, arise regarding it, both of which have been the occasion of much controversy even among Catholics themselves: (1) as to the subject—the seat or the organ of this infallibility, and (2) as to the object—the matters to which it extends.
As to the first, all Catholics have been agreed that the body of bishops, morally speaking, throughout the church, acting in common with the pope, constitute the most perfect organ of the infallibility of the church; and hence, that when they unite in any way, whether assembled in a general council or separated in place, their judgment is infallible. Thus, if a doctrinal decree was addressed officially by the pope to the whole church, and either expressly confirmed or tacitly accepted by the bishops, this decree was held to be infallible. In like manner, if a doctrinal decree, emanating even from a local council, as that of a national, or even a provincial church, was universally accepted by the pope and the bishops, that decree also was held to be infallible. In a word, wherever there is found the united judgment of the pope and the bishops, all have agreed in accepting it as the infallible judgment of the church. But should the pope alone judge without the bishops, then arose the well-known dispute of the Gallican and Ultramontane divines; the latter affirming, the former denying, the papal judgment to be infallible; but all agreeing that it was not binding as an article of Catholic faith so long as it had not received the assent of the body of the bishops. By the decree of the Vatican Council (1870) this controversy was decided after much discussion; the constitution Pastor Aeternus teaches 'that when the Roman Pontiff speaks ex cathedra—that is, when he, using his office as pastor and doctor of all Christians, in virtue of his apostolic office defines a doctrine of faith and morals to be held by the whole church—he by the divine assistance, promised to him in the blessed Peter, possesses that infallibility with which the Divine Redeemer was pleased to invest his church in the definition of doctrine on faith or morals, and that therefore such definitions of the Roman Pontiff are irreformable in their own nature and not because of the consent of the church.' See POPE.
On the matters or subjects to which the gift of infallibility extends Catholics are agreed in one principle, that it embraces all those subjects, and those only, which are necessary for the maintenance of divine truth in the church. Hence, presupposing divine revelation, either written or oral, it embraces all questions of faith and morality, all subjects of general discipline, so far at least as to preclude the introduction, by authority of the church, of any discipline which should be injurious to faith or to morality. On the other hand, it does not embrace questions of science, or matters of fact, or abstract opinions unconnected with religion. On this point all Catholics have been agreed. But a very celebrated dispute arose in the 17th century, on occasion of the Augustinus of Jansenius, as to the infallibility of the church in judging of books, out of which originated the well-known Jansenist distinction of law and of fact (see JANSENISM). On this subject it will be enough to say that all Catholics are now agreed in recognising as a necessary condition to the effective infallibility that it should extend to the judgments upon books so far as to decide whether the doctrine contained therein may or may not be opposed to sound faith or morality.
[The Vatican Council produced a large literature, including Ceconi, Storia del Concilio Vaticano (1873); Frond, Actes et Histoire du Concile œcuménique de Rome (8 vols. 1870-73). Salmon's Infallibility of the Church (1889) discusses the doctrine controversially from the Protestant point of view.] See also BASEL (COUNCIL OF), POPE, ROMAN CATHOLIC CHURCH, &c., and Rev. D. Lyons, Christianity and Infallibility—Both or Neither (1892).