It has to do with the certitude giving adoration to the Eucharist, because of the dogma behind it.
The certitude is at the same level for knowing the papal claimants cannot be true popes because of their implementing the errors of Mortalium Animos throughout every corner of the Church hierarchy.
Sorry ... just not following at all. Perhaps try formulating this as a syllogism.
They could implement all kinds of "errors of Mortalium Animos" without that even invalidating the Rite.
Sounds like what your grasping for but missing the mark on is that ...
MAJOR: Pope cannot promulgate a Rite of Mass that is doubtfully valid.
MINOR: Montini promulgated a Rite of Mass that is doubtfully valid.
CONCLUSION: Montini was not the Pope.
Problem here, of course, is that the MINOR is not dogmatically certain, but we are making a private judgment. Based on the logical weakest link principle, therefore, the conclusion cannot be dogmatically certain either, since the conclusion cannot be any stronger than the weakest of its premises.
Topic: Why the Sedevacantist position is not dogma (Read 8572 times)