Over the centuries, the pope's claims of spiritual authority have been ever more clearly expressed since the first centuries, culminating in the proclamation of the dogma of papal infallibility for those rare occasions the pope speaks ex cathedra (literally "from the chair (of Peter)") when issuing a solemn definition of faith or morals. The last such occasion was in the year 1950 with the definition of the dogma of the Assumption of Mary.The office of pope has often been controversial among the Eastern Orthodox, Protestants, secular rulers, and sometimes within the Catholic Church itself.Roman Catholics say that the primacy of the papacy derives from Jesus Christ himself, while non-Catholic historians see the primacy of the pope as arising out of hundreds of years of church tradition. All agree that the Pope's role developed through history.
