The Facts on Roman Catholicism (Harvest House, 1993), p. 38
Is the Pope infallible?
The Catholic Church teaches that when the Pope speaks “ex cathedra” (i.e., “from his chair” or authoritatively*), he is infallible in matters of faith and morals.
Papal infallibility was officially defined and promulgated on July 18,1870 at the first Vatican Council.* What this means is that for 1,870 years the Catholic Church did not officially teach that the Pope was infallible. Even within the Council itself, there were many protests, and a large number of other faithful Catholics rejected it as well, earning for themselves the title “Old Catholics.”*
We grant that most papal statements are not made under the strictures of the 1870 ex cathedra definition. But that is not the issue. Rather, the issue is that such pronouncements in general uphold the doctrinal position of Catholicism overall.
A thorough discussion of the Vatican I Council can be found in August Bernard Hasler’s How the Pope Became Infallible….*
Papal infallibility has never been a credible doctrine. As Carson points out in his study of contemporary Catholicism, the doctrine of an infallible Pope and/or Church reasonably assumes that the infallible guide will first of all be clearly recognizable; second, that this guide will act with reasonable promptitude in discerning truth from error; and third, that this guide can never be responsible for leading the Church into error.* But in the history of the Catholic Church, this has not been the case.
*For full documentation, please see The Facts on Roman Catholicism.