Anti Pope

[dominikus28]

How exactly does the church know which were past anti popes?
How can they tell who was the real one and the fake one?

 

[Dale_M]

The real one can infallibly declare the other one false.



According to the Wikipedia article (take that as you may),

In its list of the Popes, the Holy See’s annual directory, Annuario Pontificio, attaches to the name of Pope Leo VIII (963-965) the following note: “At this point, as again in the mid-eleventh century, we come across elections in which problems of harmonizing historical criteria and those of theology and canon law make it impossible to decide clearly which side possessed the legitimacy whose factual existence guarantees the unbroken lawful succession of the Successors of Saint Peter. The uncertainty that in some cases results has made it advisable to abandon the assignation of successive numbers in the list of the Popes.”

Well, in any event, I trust that the Holy Spirit has kept the Church from error.