The Catholic Church was, therefore, a vast human society, believed to be of divine foundation and sanction, and with a mission greater and more lofty than that of any other organization. Church and state had each its own sphere, but the Church had insisted for centuries that it was greater and more necessary than the state. The members of the Church were the sum-total of Christian believers who had been baptized --practically the population of western and central Europe--and its officers constituted a regular governing hierarchy. [Sidenote: Head of the Church] At the head of the hierarchy was the bishop of Rome, styled the pope or sovereign pontiff, who from the first had probably enjoyed a leading position in the Church as the successor of St. Peter, prince of the apostles, and whose claims to be the divinely appointed chief bishop had been generally recognized throughout western Europe as early as the third century--perhaps earlier. The bishop of Rome was elected for life by a group of clergymen, called cardinals, who originally had been in direct charge of the parish churches in the city of Rome, but who later were frequently selected by the pope from various countries because they were distinguished churchmen. The pope chose the cardinals; the cardinals elected the pope. Part of the cardinals resided in Rome, and in conjunction with a host of clerks, translators, lawyers, and special officials, constituted the _Curia_, or papal court, for the conduct of general church business. [Sidenote: Local Administration of the Church] [Sidenote: Secular Clergy]