This is obvious LoT as why would a Pope need a cofessor if this were not the case. Tell us something we don't know.
I would like U or anyone else to show a history book, Papal Allocution, theological text or any other evidence that there even is such a thing as a 'sede vacantist' or 'sede vacantism'.
In all the past 10 yrs of studying Church history, I have never run across either term until D Hobson once asked me on the phone if I was one.
My first reaction was one of dismay as I immediately wondered how Pope Gregory XVII can be Pope and the chair of Peter to be vacant at the same time.