St Optatus, of Mela in Africa, addressing the Donatists: “To err knowingly is a sin: the ignorant are some times pardoned. You cannot deny that you know the Episcopal chair in the city of Rome was first bestowed on Peter: that Peter, the head of all the Apostles, sat therein; in which one chair unity should be preserved by all—so that now, whoever would place another chair against this one, would be guilty of schism.” (S. Optatus)