This term is employed in an ecclesiastical and in an historical signification. In the former of these uses it denotes the ecclesiastical system in which the pope as successor of St. Peter and Vicar of Jesus Christ governs the Catholic Church as its supreme head. In the latter, it signifies the papal influence viewed as a political force in history. (See APOSTOLIC SEE; APOSTOLIC SUCCESSION; CHURCH; PAPAL ARBITRATION; POPE; UNITY.)