(Greek Hierarchia; from Hieros, sacred; archein, rule, command)

This word has been used to denote the totality of ruling powers in the Church, ever since the time of the Pseudo-Dionysius Aeropagita (sixth century), who consecrated the expression in his works, The Celestial Hierarchy and The Ecclesiastical Hierarchy (P. G., III, 119 and 370). According to this author the word connotes the care and control of holy or sacred things. The Hierarcha, it is here explained, is he who has actual care of these things; who, indeed, both obeys and commands. There is, consequently, a necessary gradation among hierarchs. The hierarchy, therefore, connotes the totality of powers established in the Church for the guiding of man to his eternal salvation, but divided into various orders or grades, in which the inferior are subject to and yield obedience to the higher ones. 

When Christ instituted the Twelve apostles, He constituted them in the form of a college or permanent assembly, at the head of which he placed Peter, chosen from among them. St. Peter and the rest of the apostles constitute a single apostolic college.

The Lord made Simon alone, whom named Peter, the rock of His Church. He gave him the keys of His Church and instituted him shepherd of the whole flock (Mt. 16:18-19). The office of binding and loosing which was given to peter was also assigned to the college of apostles united to its head. This pastoral office of Peter and the other apostles belongs to the Churchs very foundation and is continued by the bishops under the primacy of the Pope.

The Pope, bishop of Rome and Peters successor, is the perpetual and visible source and foundation of the unity both of the bishops and of the whole company of the faithful. The Roman Pontiff, by reason of his office as Vicar of Christ, and as pastor of the entire Church has full, supreme, and universal power over the whole Church.

The Patriarch is the father and head of a particular church legitimately recognized by the supreme authority of the Church . A patriarch is a bishop who has power over all the bishops including metropolitans and other Christian faithful of the Church over which he presides. (se EASTERN CHURCHES).

The college or body of bishops has no authority unless united with the Roman Pontiff, Peters successor, as its head. The college of bishops exercises power over the universal Church in a solemn manner in an ecumenical council. The individual bishops are the visible source and foundation of unity in their own particular churches. As such, they exercise their pastoral office over the portion of the People of God assigned o them, assisted by priests and deacons.