Q: Whether Only a Bishop Can Confer This Sacrament?

A: On the contrary,
Pope Eusebius (Ep. iii ad Ep. Tusc.) says: "The sacrament of the imposition of the hand should be held in great veneration, and can be given by none but the high priests. Nor is it related or known to have been conferred in apostolic times by others than the apostles themselves; nor can it ever be either licitly or validly performed by others than those who stand in their place. And if anyone presume to do otherwise, it must be considered null and void; nor will such a thing ever be counted among the sacraments of the Church." Therefore it is essential to this sacrament, which is called "the sacrament of the imposition of the hand," that it be given by a bishop.

I answer that,
In every work the final completion is reserved to the supreme act or power; thus the preparation of the matter belongs to the lower craftsmen, the higher gives the form, but the highest of all is he to whom pertains the use, which is the end of things made by art; thus also the letter which is written by the clerk, is signed by his employer. Now the faithful of Christ are a Divine work, according to 1 Cor. 3:9: "You are God's building"; and they are also "an epistle," as it were, "written with the Spirit of God," according to 2 Cor. 3:2, 3. And this sacrament of Confirmation is, as it were, the final completion of the sacrament of Baptism; in the sense that by Baptism man is built up into a spiritual dwelling, and is written like a spiritual letter; whereas by the sacrament of Confirmation, like a house already built, he is consecrated as a temple of the Holy Ghost, and as a letter already written, is signed with the sign of the cross. Therefore the conferring of this sacrament is reserved to bishops, who possess supreme power in the Church: just as in the primitive Church, the fulness of the Holy Ghost was given by the apostles, in whose place the bishops stand (Acts 8). Hence Pope Urban I says: "All the faithful should, after Baptism, receive the Holy Ghost by the imposition of the bishop's hand, that they may become perfect Christians."

Reply Obj. 1: The Pope has the plenitude of power in the Church, in virtue of which he can commit to certain lower orders things that belong to the higher orders: thus he allows priests to confer minor orders, which belong to the episcopal power. And in virtue of this fulness of power the Pope, Blessed Gregory, allowed simple priests to confer this sacrament, so long as the scandal was ended.

Reply Obj. 2: The sacrament of Baptism is more efficacious than this sacrament as to the removal of evil, since it is a spiritual birth, that consists in change from non-being to being. But this sacrament is more efficacious for progress in good; since it is a spiritual growth from imperfect being to perfect being. And hence this sacrament is committed to a more worthy minister.

Reply Obj. 3: As Rabanus says (De Instit. Cleric. i), "the baptized is signed by the priest with chrism on the top of the head, but by the bishop on the forehead; that the former unction may symbolize the descent of the Holy Ghost on him, in order to consecrate a dwelling to God: and that the second also may teach us that the sevenfold grace of the same Holy Ghost descends on man with all fulness of sanctity, knowledge and virtue." Hence this unction is reserved to bishops, not on account of its being applied to a more worthy part of the body, but by reason of its having a more powerful effect.