Why priests are different.
1 It is, of course, clear from what has been said that in all the sacraments dealt with a spiritual grace is conferred in a mystery of visible things. But every action ought to be proportioned to its agent. Therefore, the sacraments mentioned must be dispensed by visible men who have spiritual power. For angels are not competent to dispense the sacraments; this belongs to men clothed in visible flesh. Hence, the Apostle says: “Every high priest taken from among men is ordained for men in the things that appertain to God” (Heb. 5:1).
2 This argument can be derived in another way. The institution and the power of the sacraments has its beginning in Christ. For the Apostle says of Him: “Christ loved the Church and delivered Himself up for it: that He might sanctify it, cleansing it by the laver of water in the word of life” (Eph. 5:75-26). It is also clear that Christ gave the sacrament of His body and blood at the Last Supper, and ordered it to be frequented; and these are the principal sacraments. Therefore, since Christ was about to withdraw His bodily presence from the Church, it was necessary that Christ should establish other ministers in His place who would dispense the sacraments to the faithful; in the Apostle’s words: “Let a man so account of us as ministers of Christ and dispensers of the mysteries of God” (1 Cor. 4:1).
And so He committed the consecration of His body and blood to the disciples, saying: “Do this in commemoration of Me” (Luke 2:19); the same received the power of forgiving sins, in the words of John (20:2.3): “Whose sins you shall forgive, they are forgiven them”; the same also were given the duty of teaching and baptizing, when He said: “Going, therefore, teach ye all nations, baptizing them” (Mat. 28:19). But a minister is compared to his lord as an instrument to its principal agent, for, as an instrument is moved by the agent for making something, so the minister is moved by his lord’s command to accomplish something. Of course, the instrument must be proportionate to the agent.
Hence, the ministers of Christ must be in conformity with Him. But Christ, as the Lord, by His very own authority and power wrought our salvation, in that He was God and man: so far as He was man, in order to suffer for our redemption; and, so far as He was God, to make His suffering salutary for us. Therefore, the ministers of Christ must not only be men, but must participate somehow in His divinity through some spiritual power, for an instrument shares in the power of its principal agent. Now, it is this power that the Apostle calls “the power which the Lord bath given me unto edification and not unto destruction” (2 Cor. 13:10).
3 One must not say, of course, that power of this sort was given by Christ to His disciples in such a way as not to flow on through them to others; it was given “for building up the Church,” in the Apostle’s phrase. So long, then, must this power be perpetuated as it is necessary to build up the Church. But this is necessary from the death of the disciples of Christ to the very end of the world. Therefore, the spiritual power was given to the disciples of Christ so as to pass on from them to others. Hence, also, our Lord used to address His disciples in the person of other believers. Thus, we have in Mark (13:37): “What I say to you, I say to all”; and in Matthew (28:20) our Lord said to the disciples: “Behold, I am with you all days even to the consummation of the world.”
4 This spiritual power from Christ, then, flows into the ministers of the Church; the spiritual effects on us, of course, derived from Christ, are fulfilled under certain sensible signs, as is clear from the foregoing; therefore, this spiritual power also had to be passed on to men under certain sensible signs. But fixed forms of words and determined acts are of this sort: the imposition of hands, for example, the anointing, and the offering of the book or the chalice, or of something of this sort which belongs to the execution of the spiritual power. But, whenever something spiritual is transferred under a bodily sign, we call it a sacrament. Clearly, then, in conferring the spiritual power, a certain sacrament is enacted which is called the sacrament of orders.
5 Now, this belongs to the divine liberality: that, if the power for some operation is conferred on one, there be conferred also those things without which this operation cannot suitably be exercised. But the administration of the sacraments to which the spiritual power is ordered is not suitably done unless one be helped to it by divine grace. Accordingly, grace is bestowed in this sacrament as it is in the other sacraments.
6 Now, the power of orders is established for the dispensation of the sacraments. But among the sacraments that which is most noble and tends most to complete the others is the sacrament of the Eucharist as is clear from what has been said. Therefore, the power of orders must be weighed chiefly by reference to this sacrament, for “everything is denominated from its end.”
7 It seems, of course, to be the same power which grants a perfection, and which prepares matter for the reception of that perfection. just so, fire has the power both to pass its form on to another, and to dispose that other for the reception of the form. Since, then, the power of orders is extended to performing the sacrament of the body of Christ and handing it on to believers, the same power must extend itself to this: making the believers ready for this sacrament and in harmony with its reception. But a believer is made ready for the reception of this sacrament and in harmony with it by his freedom from sin; otherwise, he cannot be united spiritually with that Christ to whom he is sacramentally conjoined by the reception of this sacrament.
Therefore, the power of orders must extend itself to, the remission of sins by the dispensation of those sacraments which are ordered to the remission of sins; baptism and penance are of this kind, as is clear from what has been said. Hence, as was said, our Lord’s disciples, to whom He committed the consecration of His body, were also given the power to forgive sins. This, indeed, is the power we understand by the “keys” about which our Lord said to Peter: “I will give to you the keys of the kingdom of heaven” (Mat. 16:19). For to every man heaven is closed or is opened by this: he is subject to sin, or he is cleansed from sin; hence, too, the use of these keys is called “to bind and to loose”, namely, from sins. It was of these, indeed, keys that we spoke above.