Father David R. Belland writes to Abyssum out of his deep felt concern and love for the Church.
He suggests that If Our Lord promised that “the gates of hell shall not prevail against it,” His Bride, He means it. Yet, what if a man who claims to be a pope becomes a heretic or seemingly teaches heresy? That question has been pondered down the ages, and to this day no absolute answer has really been provided. In fact, for all the hypothetical scenarios concerning heresy, the possible solutions proposed by the learned theologians are just that: possible, but not in any way certain. Michael Davies in his book, I Am with You Always: The Divine Constitution and Indefectibility of the Catholic Church, says the following:
Saint Robert was (in De Romano Pontifice Vol. II, chap. 30, p. 720), of course, discussing a theoretical possibility, and believed that a pope could not become an heretic and thus could not be deposed, but he also acknowledged that the more common opinion was that the pope could become an heretic, and he was thus willing to discuss what would need to be done if, per impossible, this should happen: ‘This opinion (that the Pope could not become an heretic) is probable and easily defended. . . . Nonetheless, in view of the fact that this is not certain, and that the common opinion is the opposite one, it is useful to examine the solution to this question, within the hypothesis that the Pope can be an heretic’ [De Romano Pontifice, Vol. II, chap.30, p.418]. The great Jesuit theologian, Francisco de Suarez (1548-1617) was also sure that God’s ‘sweet providence’ would never allow the one who could not teach error to fall into error, and that this was guaranteed by the promise Ego autem rogavi pro te… (Luke 22:32). But, like Bellarmine, Suarez was willing to consider the possibility of an heretical pope as an hypothesis, particularly in view of the fact, he claimed, that several ‘general councils had admitted the hypothesis in question’ [De legibus, vol. IV, chap. 7, no. 10, p 361]. Saint Alphonsus Ligouri (1696-1787) did not believe that God would ever permit a Roman Pontiff to become a public or an occult (secret) heretic, even as a private person: ‘We ought rightly to presume as Cardinal Bellarmine declared, that God will never let it happen that a Roman Pontiff, even as a private person, become a public heretic or an occult heretic’ [Dogmatic Works of St. Alphonsus Maria de Ligouri, Vol. VIII, p. 720].”
 Michael Davies, I Am With You Always: The Divine Constitution and Indefectibility of the Catholic Church, New rev. ed. 1997, The Neumann Press, Long Prairie, Minnesota, 1997, pp. 44 – 4 )
Certainly, God would not allow his Church to be left in the dust of doubt either with regard to Faith or with regard to Morals. Considering the reality of the situation in the Church today, therefore, one that is absolutely unparalleled, indeed exceptional, can one really look to the past for a solution, which no one has actually demonstrated to be absolutely workable for past crises, or to merely theoretical scenarios envisioned for the future? Yet, those theoretical problems discussed in the past in no way even remotely approach the unprecedented reality here and now.
The mind of Father David R. Belland resolutely balks at the idea. He asks: “Does it not seem more likely that the unprecedented reality of today demands an unprecedented concrete solution? And can you guess what’s coming; yes, you’re right, Benedict is that unprecedented, yet concrete, solution that if looked into can be seen as that unquestionable protection of God.”
Perhaps a better way of stating the QUESTION is this.
A man who occupies the Chair of Peter is called the Pope.
A man who occupies the Chair of Peter seems to be a public heretic or occult heretic, yet it is not reasonable that God would ever permit a Roman Pontiff to become a public or an occult (secret) heretic, even as a private person:
Ergo, such a man who occupies the Chair of Peter is not the Pope.