“We know who the pope is now, and we know who the pope was then. There were not three popes. There can’t be.”
Hope you like Wiki...
http://en.wikipedia.org/wiki/Western_Schism
“According to Broderick:
“Doubt still shrouds the validity of the 3 rival lines of pontiffs during the 4 decades subsequent to the still disputed papal election of 1378. This makes suspect the credentials of the cardinals created by the Roman, Avignon, and Pisan claimants to the Apostolic See. Unity was finally restored without a definitive solution to the question; for the Council of Constance succeeded in terminating the Western Schism, not by declaring which of the 3 claimants was the rightful one, but by eliminating all of them by forcing their abdication or deposition, and then setting up a novel arrangement for choosing a new pope acceptable to all sides. To this day the Church has never made any official, authoritative pronouncement about the papal lines of succession for this confusing period; nor has Martin V or any of his successors. Modern scholars are not agreed in their solutions; although they tend to favor the Roman line.”[1]”
You posted:
“Doubt still shrouds the validity of the 3 rival lines of pontiffs during the 4 decades subsequent to the still disputed papal election of 1378.”
Nope. Not among Catholics. And it is the Catholic Church who must be relied on as to who was pope. Thus, there is no issue here. Just as the USA decides who is president, the Church says who is pope. Period.
“Modern scholars are not agreed in their solutions; although they tend to favor the Roman line.”
The Church has always said it was the Roman obedience. End of story.
There were several men who claimed to be pope. These men has successors who forwarded that claim. Not until a Council did they finally fasten on one man. the office itself remained undivided, so eventually they had to sort out whose actions would stand as official. Again: the principle of a papacy was never challenged until Luther”s time.