You're arguing pretty hard for something that even you claim doesn't make sense. Now that we both agree that what you've been saying doesn't make sense - which is kind of what I've been driving at - I have to get back to work.
Since Urban VI was the rightful Pope, it follows that the other claimaints were not, and that the successors of Urban VI (Boniface IX, Innocent VII, and finally Gregory XII) were also rightful Popes.
But Gregory XII papacy was renunciated. Even though he was the rightful Pope, chosen by God through election. Doesn't this mean (by your own "rules") that the entire Catholiuc Church as it stands today is not Catholic, because they've all been revering and listening to false Popes since 1418?
... all someone has to do is believe they’re a Christian in order to be a Christian and that idea is demonstrably and unequivocally false.
You have utterly failed to demonstrate that.
Whoever gets the 2/3 majority needed is the person that was chosen by God. Full stop.
And that's actually demonstrably wrong.
The papacy had resided in Avignon since 1309, but Pope Gregory XI returned to Rome in 1377. The Catholic Church split in 1378 after Gregory XI's death and Urban VI's election.
This makes Urban VI Pope.
A group of French cardinals declared his election invalid and elected Clement VII as pope.
Now who is the rightful Pope? Urban VI or Clement VII? If your "full stop" applies, then the answer is Urban VI, even if the French cardinals were correct that his election was invalid. Or do invalid elections not count, which would make Clement VII the rightful Pope?
After [over forty years and] several attempts at reconciliation, the Council of Pisa (1409) declared that both rivals were illegitimate and elected a third purported pope [Alexander V].
There's another election - is Alexander V the rightful Pope now?
The schism was finally resolved [nine more years later] when the Pisan claimant Antipope John XXIII called the Council of Constance (1414–1418). The Council arranged the renunciation of both Roman pope Gregory XII [whose election was handed down through Urban VI] and Pisan antipope John XXIII [who was elected after Alexander V]. The Avignon antipope Benedict XIII [he was elected after Clement VII] was excommunicated, while Pope Martin V [finally, back to one Pope] was elected and reigned from Rome.
In 1409, who was the rightful Pope? Was it Benedict XIII, or Gregory XII, or Alexander V?
... if they’re not a high quality version of that thing.
And who is the arbiter of quality, and who draws the line in the sand?
I know this has all kind of devolved into a semantic argument, and a weird discussion about Popery, and I think at this point it's worth reiterating my initial point: If someone claims to belong to a religion, they do. Whether that claim enables anyone to make predictions or judgments about a person's other statements or actions is another question entirely.
You're talking about "the Catholic Church and its deity is the very end of any discussion about who is the rightful Pope," and I'm talking about "But it has happened that multiple people, each with their own supporters, claimed to be the rightful Pope at the same time."
When that happens, which one of those is "the Catholic Church"? In the moment, there is no way to tell. Looking back across history, we can see the outcome.
I'm really not sure why this is hard for you to comprehend, or why you're entirely hung up on Catholic dogma.
Again, history is written by the victors. It "just so happens" that the Pope is the Pope because the portion of the Catholic Church which says he's the Pope has the social, economic, and political power to make that "true." Which would be the case no matter which portion achieved that set of powers; we could just as easily be referring to a whole different set of Popes, past and present.
I'm not talking about how they view or define themselves. If Catholic dogma wants to say that that's what God intended, that's fine. Neither of us has to believe it. If some other set of Popes ended up existing, that would have been "what God intended."
The Catholic Church is founded on the idea that the Pope is the mouthpiece of god.
Who decides who the "right" Pope is? You must certainly know that issues of succession (oh so topically) are often contested, and the Catholic Church is not immune to that.
Absolutely right. Nobody really wanted to sponsor Columbus because they already knew how big the globe was, and that Columbus' proposed expedition would run out of supplies before he got to east Asia by going west - because they were unaware of the Americas existing.
The earliest globe that still exists was started in 1490, and finished in 1492, the very year that Columbus set sail. Columbus didn't return to Spain until March 15, 1493.
Whether someone is a "vegan" depends on behavior in ways that "Christian" doesn't. Even so, being "vegan" - even when the person does not directly and knowingly consume animal products - completely ignores the fact that they are indirectly making use of animal products, because they depend on a society that currently uses animal products, and where that society got to the technological level it's at through the use of animal products over many millenia.
And we're back to No True Scotsman, adjusting the definition to fit the circumstances.
If someone claims they’re a “Christian” but don’t believe in Jesus, then they’re not a Christian.
That's fair. It still hinges on a belief claim only. Based on a person's other actions, you can doubt that claim, but the singular authority for what a person actually believes is what that person claims to believe.
If someone claims to be "a Christian," they are. There is no other qualification. Whether such a person adheres more or less to common Christian principles is a separate issue, let alone that there are so many splinter groups of "Christians" that the phrase "common Christian principles" barely has any meaning anyway.
Something I didn't even realize I wanted was to not have some eyeball-pulling algorithm recommending things to me. It's lovely.