How the Pope became infallible
As a violent thunderstorm raged above St. Peter's Basilica in Rome on July 18, 1870, the bishops of the First Vatican Council adopted a decree that would alter Christian history. A Pope, they declared, is infallible when he defines doctrines of faith or morals ex cathedra (from his throne) and such dicta are "irreformable" and require no "consent of the church." The bishops' lopsided 533-to-2 vote that day masked a deep division in the council and throughout the church. The immediate repercussions included the schism of "Old Catholics" and...