I don't think it's a heresy. Yet. I just think it's unjust to separate yourselves from other sedevacantists, as if we don't want a Pope, as if we are some lower species because we don't have an imaginary friend as Pope. Roscoe especially is incredibly aggravating when he tries constantly to disassociate himself from... Himself. Because whether he likes it or not, he is a sedevacantist.
You can see the same desperation in the "sedeprivationist" theory. The Popes under this so-called "Cassiacuм thesis" are material but not formal Popes. And the priests and bishops with invalid Holy Orders are therefore material but not formal priests and bishops. So we have an entire Church of material but not formal clergy -- a ghost Church, a Through the Looking Glass church. If all these ghost priests, ghost bishops and their ghost Pope suddenly have a change of heart, if they recant their errors, THEN they will be restored formally to the faith and it will once again be the Catholic Church.
Granted. If they renounce their errors, it will be. But they are not going to. And in the meantime, all those who don't make a clean break are weakening the resistance, the real Church, which is now in eclipse.
The human capacity for self-delusion really is limitless.
Sedeprivationists and Siri-ites hinder unity in an emotional sense, but not in a real sense. In general, parentsfortruth and roscoe agree with the detested "sedes" on the essentials. We probably go to the same kind of sede/trad churches. For that reason I can't say they're being divisive.
But their acolytes do show a certain reluctance to face reality -- a reluctance I understand, as nothing is harder for a Catholic than to say there is no Pope. But that doesn't change the fact that we DO NOT HAVE A POPE. Even if one is being kept in a cage somewhere in Vietnam, with bamboo shoots being shoved under his fingernails, suffering for the faith, he still can't guide us or teach us. This is why I say that the dreaded term "sedevacantism" reflects our predicament perfectly.
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The "other side" is not so kind. I recall David Hobson saying that Bishop Pivarunas of CMRI "holds the heresy of popeless ecuмenism." Does he even know what "ecuмenism" means? And how is saying that we're without a Pope a heresy? The Church is not only without a Pope whenever one Pope dies, but there have been times where people were confused about the very identity of the Pope.
Siri-ites, I must question your discernment of spirits if fast-talking hucksters like Hobson and Malachi Martin are the guys you really want to follow. You need better spokesmen, and badly. I read all through Hobson's website and he has no proof of Siri being Pope, he just tells us to blindly believe it because he says so. Well, who are you, David Hobson?