Sedevacantism is the position held by a minority of traditionalist Catholics, that the present occupant of the papal see is not truly the Pope, the See has been vacant since the death of Pope Pius XII in 1958.
Sedevacantism is the position, the See has been vacant since the death of Pope Pius XII in 1958. The present occupant of the papal see is not truly the Pope. This was what this position is held by a minority of traditionalist Catholics.