8 The human race has always felt the need of a priesthood: of men, that is, who have the official charge to be mediators between God and humanity, men who should consecrate themselves entirely to this mediation, as to the very purpose of their lives, men set aside to offer to God public prayers and sacrifices in the name of human society. For human society as such is bound to offer to God public and social worship. It is bound to acknowledge in Him its Supreme Lord and first beginning, and to strive toward Him as to its last end, to give Him thanks and offer Him propitiation. In fact, priests are to be found among all peoples whose customs are known, except those compelled by violence to act against the most sacred laws of human nature. They may, indeed, be in the service of false divinities; but wherever religion is professed, wherever altars are built, there also is a priesthood surrounded by particular marks of honor and veneration.
Source: Ad Catholici Sacerdotii (Vatican.va)