With respect, you are making a strawman here. Even if a Pope cannot lose his Office due to heresy, a Pope losing his office is not the belief of all Sedevacantists. A significant portion believe that the election of Roncalli was invalid. Though, I am sure this is not news to you.

Hello hgodwinson and welcome to the debate.

The idea of believing in an invalid election, like believing in the pope is not the pope, is only opinion. That's all it is.
Like +ABL saying one day we may say the pope is not the pope - that was his opinion at that time. Like the saints and fathers who taught a heretic pope loses his office, this was their opinion at that time. The whole idea of sedeism is nothing more that opinion that among many, has morphed and been elevated into a de fide doctrine of the Church - without the Church ever having believed or taught it.   

A lot of crazy thinking is corrected by clear challenges, and there have been many, many challenges that have been presented to the sedes for their consideration right here on CI that either go unanswered or are completely ignored, such as the post you replied to - presumably because there is no getting around the truth of it, and in order to wholly accept that truth, the sede belief is threatened. So it is another challenge placed into the ignored-by-sede file, which is a huge file btw.

After posting this, and to show you what I mean in reference to the underlined above, here is a quote by a sede from another sede thread....

Incidentally, The Archbishop actually knew the principles involved with the “heretic pope question”. He knew that if JPII was, to his mind, a pertinacious heretic, he would have lost his “pontificate”. This is a fact. With Bergoglio on the scene, R&Rers, such as yourself, know that this Catholic doctrine is now provable, so now you needed to switch gears and deny the doctrine.

Unfortunately, we have some Old Catholics here posing as Catholics, so readers need to be aware.

Agreed! You Old Catholic you!

So, the fact that you have it exactly backwards is a window into how messed up your mind has gotten.

Always remember:
Catholics through all the generations of the Church have always believed that there are two ways for a pope to lose his office, 1) his death or 2) his resignation. This is what I believe. This is Catholic.

If you remember this, you will be unable to believe there's any other way for a pope to lose his office without changing what Catholics believe.

Tell that to St. Robert Bellarmine or to those who hold 4 of the 5 Opinions regarding that question.  This is a disputed matter and your assertion that "what Catholics believe" is that minority opinion that was held by only 1 or 2 theologians tops (and now +Schneider) is absurd on the face of it.  You're basically saying that Bellarmine, Cajetan, John of St. Thomas and others are not "Catholic", once again demonstrating that for you, Stubborn is the litmus test for what's "Catholic".

"What Catholics believe" is what Archbishop Lefebvre articulated, namely, that the Papacy is guided and protected by the Holy Spirit and prevented from changing the Church so much that Catholics must sever communion with and subjection to the hierarchy in order to remain Catholics.

On the other hand, as Hgodwinson points out, the reasons why Sedes believe the pope has lost his office are MANY.  So it’s not like there’s a uniform explanation.  A fact that many Sedes forget.

You're confusing explanations for the "how and why" of the V2 papal claimants not being legitimate popes for the doctrinal rationale behind it, namely, the belief of Catholics that the Papacy is guided and protected by the Holy Spirit from damaging the Church this badly through the Magisterium, the Mass, etc. ... a principle upheld by Archbishop Lefebvre.  This is the chief driving doctrinal factor behind sedevacantism, upon which sedevacantism rests, but which sedevacantists do often forget and allow themselves to be embroiled in battles over the "5 Opinions".  That is why I've referred to myself as a dogmatic indefectibilist, rather than as a sedevacantist or even sedeprivationist.  If someone wanted to claim that Montini was drugged, chained down in a dungeon beneath the Vatican, and replaced by a big-eared crooked-nosed double, while I wouldn't by it, I would have no principled objection to it.  Or if someone wanted to claim that Montini was not acting freely but under blackmail, I could almost believe that (given the allegations about Montini's lifestyle).  I'd have no principled objection to it, but might disagree about these particular explanations for the "how and why".

It was precisely over the varying possible explanations of the "how and why" that prevented him from definitively ("solemnly and officially" as he said) embracing SVism, though he maintained that it was possible.

Stubborn, to be fair, every crisis/heresy in the church, throughout history, was a “first”.  Just because something has never happened before, doesn’t mean it can’t happen.  There’s no doctrine which says the pope can’t lose his office due to heresy.  Only a “pious belief”.

On the other hand, as Hgodwinson points out, the reasons why Sedes believe the pope has lost his office are MANY.  So it’s not like there’s a uniform explanation.  A fact that many Sedes forget.

Conclusion- We live in unprecedented times.  God has allowed this Tribulation to be (as Scripture says) the worst that has been, and will be.  Let’s not draw lines in the sand on what God will/won’t allow.  Whatever happens, however horrible, He will be with us.  But we really don’t know His limits.

Sorry Pax, you say there is no doctrine, but I quoted what sedes believe is indeed "the doctrine" which was posted by a sede. Yes, there is no denying these are unprecedented times, but these times do not reward any of us the right to determine the status of popes - nor do we have any reason whatsoever to even attempt to do such an absurd thing.

Look at Lad, he consistently portrays +ABL, of all people, as "leaning" sede even tho a few months before he died he clearly stated that he always warned against it and explained why. The guy has blinded himself in order to cling to a useless belief - while excoriating as heretics those who prove he is wrong. This is what sedeism does to some faithful people....as +ABL said, it is a danger.

for the doctrinal rationale behind it, namely, the belief of Catholics that the Papacy is guided and protected by the Holy Spirit from damaging the Church this badly through the Magisterium, the Mass, etc. ... a principle upheld by Archbishop Lefebvre.

Yes, this is a general principle, but it's too general.  Which is why 1,000 people can apply it in a 1,000 different ways.