Readers will be aware that I do not enable any comments which even delicately hint at anything even remotely like Sedevacantism. Even if a Bishop of Rome were personally a heretic, even if, like Pope Honorius I, he actually promoted and propagated heresy, he would still be pope. I have no doubt whatsoever about this. And it is the duty of every Catholic to be in Full Communion with him. Sedevacantism is illogical and unhistorical rubbish.
But I must admit that I have no worked-out solution to the following very hypothetical hypothesis.
Suppose a pope were, additionally, to require of every Catholic explicit assent ex animo to heresy as a necessary condition for Communion with himself, what would be the situation?
I think this is humanly impossible in the current pontificate, because PF likes to operate by creating a mess and being imprecise and trusting to Time being more powerful than Space. It is inconceivable that he would waste the energy which would be needed to be precise enough to specify a heresy in a way that would be juridically watertight. Moreover, he would run the risk of putting himself in danger, and I think he is far too fly an individual to do that. Genuinely, I am asking about something genuinely hypothetical.
I'm not terribly keen on receiving lots of ranting comments, either one way or the other. But I would value sober and sensible materials for a solution to this problem. Especially, historical analogues. Unless you feel that this scenario, like an erroneous ex cathedra definition, is something the Holy Spirit can be relied on simply to prevent.
Does S Athanasius ...
And, yes, poor Dr Doellinger is a terrible warning to us all about the dangers inherent in getting answers to this sort of question wrong ...