Fr. Luther in front of Bishop Thomas Cajetan – Painting by Ferdinand Willem Pauwels (1872)
I think one of the problems that many Catholics will have here is the supposition that one could use the remote rule of faith (the past teaching of the Magisterium) as a standard by which to measure a given Pope’s teaching. For, many converts into Catholicism have converted on the precise advertisement that, contrary to their prior experience as Protestants, one would not need to ever exercise private judgement against the Magisterium of holy Church. To this it should be said that Catholicism in no way allows the obliteration of the marriage between faith & reason. I understand that we have some Catholics who have vowed to obey the teaching of the Pope whether it accords with [their] reason or not, but we should be careful. Because of the nature of Revelation and the Decrees of Vatican I on faith, revelation, and reason, there cannot be a doctrine of Christ which is contra-reason, or violates reason. Transcend and exceed reason ? Sure. But not violate such that an internal incoherence could be found. A perfect example would be the law of non-contradiction. We know that Jesus Christ died, buried, and was risen in bodily form. If therefore a Pope were to come along, shimmy his imagination, and teach that it is permissible to believe that Jesus only rose spiritually in some invisible manner, then we would have a contradiction, and anyone should be able to recognize that such a teaching is wrong, and, more importantly, not an authentic reflection of the Church’s magisterium.
But even still, some Catholics, whether from the popular ministries or from ultramontanist apologetics in the 19th/20th centuries, still cannot manage to picture how it can be reconciled – that a Pope’s own orthodoxy could be measured by another, namely, the Sacred Tradition and Holy Scripture. Is this not what Dr. Luther ultimately did? Is it now what the Anglican divines did when they sought to retain the episcopal tradition together with Scripture, and judged the Tridentine Pope’s wrong? If this is allowed, would we not be including the Protestant authority paradigm, i.e. private judgement?
The answer to this is herein (and anyone feel free to correct or add to it) – These Protestants had disavowed, in principle, the immediate authority of the hierarchical Church to pronounce doctrine on faith and morals. Luther did not appeal, as he was asked to by superiors, to the Church fathers for his doctrines, at least in principle, as if they were an agency to be submitted to. I understand that in the Augsburg Confession, and in the later coming Book of Concord, there would be references to Patristic texts, but ultimately, there was no recognition that said Patrimony was to be abided by with divine faith. If, therefore, St. Augustine, along with most of the Fathers, taught clearly contra sola fide, Luther would just cast them out of hand. Calvin even more so. The chief rejection was that even Councils, as well as Popes, could teach dogmatic and infallible doctrine. So Luther/Calvin and company would be ready to disavow the teaching of Popes, Councils, Fathers, and all scholastic theologians if they were to be found disharmonious with Scripture. And this is why Sola Scrpitura was so important, as a bed rock, for the rationale basis of Luther and the coming Protestants. If Scripture say X, and the Church says not-X, we go with Scripture, and that solves the problem.
The problem with this, of course, is that Scripture itself refers to the authority of the Church. So where Scripture itself witnesses to the wedded authority of Oral Tradition and the Sacred Writ, the Protestants thought safe to disregard and hold the inconsistency. Of course, they were not satisfied, and thus, picking up from the spirit of Wycliffe and Hus, who followed the former, they re-defined ἐκκλησία and ecclesia as invisible. At least, the elect, who would be divinely protected from apostacy, were invisible to the human eye, and thus there is no objective criteria with which to judge. Not even Scripture, since against the myriad of debate that would spawn in Protestant dialectic, it was the “few” who were “chosen” that rightly interpreted it.
In any case, Catholics don’t entertain these ideas. We wholeheartedly consent, with divine faith, to the divine establishment of the Church and its potential to deliberately teach dogma infallibly, as well as the indestructibility of its visible elements (at least, until the parousia of Christ). We hold to the Ecumenical Councils, the consensus of the Church fathers, the interpretations of Scripture made by the authentic and perennial teaching of the Magisterium, and the Papal decrees which come by way of “ex Cathedra”. It is to this unchanging Magisterium that we appeal as a standard because, ultimately, 
*that is the standard to which the Magisterium has vowed itself unto*. At the Vatican Council (1870), it was stated very clearly that, although the Pope, when speaking “ex cathedra” he, by “the divine assistance promised to him in blessed Peter“, can speak infallibly on fatith and morals, this assistance is never towards a “new doctrine”. It says in Chapter 4 , para. 6, on the authority of the Roman Pontiff: “For the Holy Spirit was promised to the successors of Peter not so that they might, by his revelation, make known some new doctrine, but that, by his assistance, they might religiously guard and faithfully expound the revelation or deposit of faith transmitted by the apostles.”. Thus, right there smack dab right in the middle of the Magisterial voice of the Ecumenical Council of Vatican, we have the Church telling us with supreme authority that she cannot assist the Pope in creating new doctrine, but, more importantly, only to *safeguard* the deposit of faith transmitted by the Apostles. Whatever comes out of the Pope, whether it be private statements or even acts of authentic Magisterium, though non-infallible, they are not protected, and thus may be wrong. Pope Francis himself is well aware of his own fallibility.
But one might further ask, who gets to judge what that “deposit of faith” is? Well, it is the Magisterium who gets to judge. And it is precisely to this Magisterium that we appeal to say that a Pope, whether it be Francis or another, cannot introduce novelty. And, because of the invincible wedding between faith/reason, there cannot ever be an authentic teaching of the Pope which contradicts the past. What if a Pope were to come out and say that it is a matter of morals that one should eat sandwiches with mustard instead of mayonaiise? Would we submit? Or if the Pope said it is more righteous to wear red shirts since it represents the blood of Christ? Or, more relevant, what if Pope Francis said the baptized do not need to follow even ex Cathedra teaching? Would we submit? Hans Küng, a known critic of Papal Infallibility, has achieved the Popes consent to look into the question of infallibility. Who knows where that will go.
Even still, one Catholic might ask what if the Magisterium says a certain doctrine, actually contradictory to past Magisterial teaching, is actually harmonious? Ultimately we do not believe such can be done , at least by an extraordinary exercise. The Pope does not get to re-define the laws of logic and reality. He can say that gravity actually pulls upward all day, and even say such is a matter of faith, and that it is harmonious all he wants, but that changes nothing. This is why persons who appeal to the Pope to clarify or even correct himself are actually exercising faith in the Magisterium, since we have faith that the authentic and irreformable Magisterium cannot violate the deposit of faith. If this were to happen, it would be the falsification-moment for Catholicism. And if this were to ever occur, then I would not be able to be committed to it. But I do not believe this can happen, and thankfully, it never has, and, by faith, I say it never will.
Concludimg remarks – This all might seem so redundant since the authoritative ability of the Magisterium is merely to sustain what is already known. Well, it would only be the same redundancy of the Apostles who were commissioned “to teach all things Christ had commanded” (Matt 28:18). Likewise, it would only be the same redundancy of Sacred Scripture, which forever remains unchangeable. Catholicism is not in the business of change, unless it means better fostering the single-same Gospel to one culture or another. Even then, great care is to be had in the implementation.
Erick Ybarra 