But, in a sense, that situation would be the easy one to face: it would be a situation in which matters were completely clear-cut, totally black-and-white. Much more worrying would be a situation (almost as improbable) in which the edges were blurred and it was not quite certain that a fully-frontal breach with the Paradosis was being set before us.
I will simply, and probably unnecessarily, remind you of
GENERAL GUIDELINES AND BASIC RESOURCES
(a) Regular readers will have noticed my emphasis on the Magisterial teaching of Ecumenical Councils and of Roman Pontiffs that any 'development' or 're-expression' in doctrine must be eodem sensu eademque sententia.
(b) And I regularly work into my texts that crucial statement of Vatican I, to the effect that the Holy Spirit was not promised to the Successors of S Peter so that, by His revelation, they might reveal (patefacerent) new teaching; but so that, by His assistance, they might guard and set forth the Tradition handed down through the Apostles, the Deposit of Faith.
(c) And I have written about precedents, of which that of Pope Honorius is probably the most straightforward, when popes have been wrong and have attempted to use their position even to promote heresy. Remember that Honorius was corrected, condemned and anathematised by successive Roman Pontiffs and Ecumenical Councils. So, clearly, it cannot be wrong to work openly and vigorously for the righting of such an error. If it were wrong to do so, then the errors of the pontificate of Honorius would not have been eventually righted.
(d) And, from the time of Blessed John Henry Newman, given as Patron to the Ordinariate by the wisdom of Pope Benedict XVI, there have been those who remind us of the Arian Crisis, when there was a substantial and near-universal apostasy on the part of the episcopate. As Newman put it, the Ecclesia Docens ceased to teach; its Magisterium was (not de jure but) de facto inoperative. Of course, he was delated to Rome for this, but God protected him, as He always did. With a considerable exercise of the imagination, one might possibly think of hypothetical reasons why such episcopal apostasy might be a possibility in some remote sci-fi situation.
(e) And at the end of Vatican I, Blessed John Henry even specified hypothetical circumstances in which it would be his judgement that that Council had not been, despite its appearances, a genuine Ecumenical Council of the Catholic Church. Yet, despite all this, Leo XIII made him a Cardinal and Benedict XVI beatified him. I am glad that
(f) Since we have indeed seen it all before, we are, thank God, protected against reactions which might put our very souls at risk, such as the vile error of Sedevacantism. Whatever mistake might come from any future Roman Pontiff or however many of the bishops, he would still be Pope; they would still be our bishops. We must be aware of the plans which are undoubtedly being laid even now by the Low Command at the Enemy's direct and personal orders. Sedevacantism is one of their most subtle creations.
But ... hey ... good news!! There are perhaps little glimmers of a silver lining, to be derived from our own present Holy Father's useful and most instructive praxis.
(1) When recently asked about the 2003 CDF document on homosexual orientation, our Holy Father replied "I do not remember that 2003 document of the CDF". Now: that particular piece of the Magisterium created a lot of comment, much of it adverse, which still continues today. It is not easy to believe, in a flatly tediously literal sense, that Pope Francis "does not remember" it. We must assume that this is now a morally acceptable formula of diplomatic evasion, rather like when your butler or your housemaid tells an unwelcome visitor that you are "not at home". It is, perhaps, worth remembering for use if ever any pope tries to saddle you with something disordered. Haec non memini! Practise repeating it!
(2) The current Roman Pontiff has, again and again and again, spoken of, and called for, Parrhesia. This means boldness to speak fearlessly even in situations in which to do so in the face of powerful people may appear (in worldly terms) dangerous. Accordingly, the Parrhesia so repeatedly enjoined by the Magisterium of Pope Francis I could, in the pontificate of Francis IV, be taken up by your great grandchildren and made the theological basis of a practical policy of Resistance. Never before has this interesting Greek term been so incessantly present upon the labia Magisterialia.
But, in any case, her Immaculate Heart will prevail.