Summa Theologica, by St. Thomas Aquinas, , at sacred-texts.com
We must now consider those on whom the power of the keys can be exercised. Under this head there are three points of inquiry:
(1) Whether a priest can use the key, which he has, on any man?
(2) Whether a priest can always absolve his subject?
(3) Whether anyone can use the keys on his superior?
Objection 1: It would seem that a priest can use the key which he has, on any man. For the power of the keys was bestowed on priests by Divine authority in the words: "Receive ye the Holy Ghost; whose sins you shall forgive, they are forgiven them" (John 20:22, 23). But this was said without any restriction. Therefore he that has the key, can use it on any without restriction.
Objection 2: Further, a material key that opens one lock, opens all locks of the same pattern. Now every sin of every man is the same kind of obstacle against entering into heaven. Therefore if a priest can, by means of the key which he has, absolve one man, he can do the same for all others.
Objection 3: Further, the priesthood of the New Testament is more perfect than that of the Old Testament. But the priest of the Old Testament could use the power which he had of discerning between different kinds of leprosy, with regard to all indiscriminately. Much more therefore can the priest of the Gospel use his power with regard to all.
On the contrary, It is written in the Appendix of Gratian: "It is not lawful for every priest to loose or bind another priest's parishioner." Therefore a priest cannot absolve everybody.
Further, judgment in spiritual matters should be better regulated than in temporal matters. But in temporal matters a judge cannot judge everybody. Therefore, since the use of the keys is a kind of judgment, it is not within the competency of a priest to use his key with regard to everyone.
I answer that, That which has to do with singular matters is not equally in the power of all. Thus, even as besides the general principles of medicine, it is necessary to have physicians, who adapt those general principles to individual patients or diseases, according to their various requirements, so in every kingdom, besides that one who proclaims the universal precepts of law, there is need for others to adapt those precepts to individual cases, according as each case demands. For this reason, in the heavenly hierarchy also, under the Powers who rule indiscriminately, a place is given to the Principalities, who are appointed to individual kingdoms, and to the Angels who are given charge over individual men, as we have explained above (FP, Q, AA,2). Consequently there should be a like order of authority in the Church Militant, so that an indiscriminate authority over all should be vested in one individual, and that there should be others under him, having distinct authority over various people. Now the use of the keys implies a certain power to exercise authority, whereby the one on whom the keys are used, becomes the proper matter of that act. Therefore he that has power over all indiscriminately, can use the keys on all, whereas those who have received authority over distinct persons, cannot use the keys on everyone, but only on those over whom they are appointed, except in cases of necessity, when the sacraments should be refused to no one.
Reply to Objection 1: A twofold power is required in order to absolve from sins, namely, power of order and power of jurisdiction. The former power is equally in all priests, but not the latter. And therefore, when our Lord (Jn. 20:23) gave all the apostles in general, the power of forgiving sins, this is to be understood of the power which results from receiving orders, wherefore these words are addressed to priests when they are ordained. But to Peter in particular He gave the power of forgiving sins (Mat. 16:19), that we may understand that he has the power of jurisdiction before the others. But the power of orders, considered in itself, extends to all who can be absolved: wherefore our Lord said indeterminately, "Whose sins you shall forgive, they are forgiven them," on the understanding that this power should be used in dependence on the power given to Peter, according to His appointment.
Reply to Objection 2: A material key can open only its own lock. nor can any active force act save on its own matter. Now a man becomes the matter of the power of order by jurisdiction: and consequently no one can use the key in respect of another over whom he has not jurisdiction.
Reply to Objection 3: The people of Israel were one people, and had but one temple, so that there was no need for a distinction in priestly jurisdiction, as there is now in the Church which comprises various peoples and nations.
Objection 1: It would seem that a priest cannot always absolve his subject. For, as Augustine says (De vera et false Poenitentia [*Work of an unknown author]), "no man should exercise the priestly office, unless he be free from those things which he condemns in others." But a priest might happen to share in a sin committed by his subject, e.g. by knowledge of a woman who is his subject. Therefore it seems that he cannot always use the power of the keys on his subjects.
Objection 2: Further, by the power of the keys a man is healed of all his shortcomings. Now it happens sometimes that a sin has attached to it a defect of irregularity or a sentence of excommunication, from which a simple priest cannot absolve. Therefore it seems that he cannot use the power of the keys on such as are shackled by these things in the above manner.
Objection 3: Further, the judgment and power of our priesthood was foreshadowed by the judgment of the ancient priesthood. Now according to the Law, the lesser judges were not competent to decide all cases, and had recourse to the higher judges, according to Ex. 24:14: "If any question shall arise" among you, "you shall refer it to them." It seems, therefore, that a priest cannot absolve his subject from graver sins, but should refer him to his superior.
On the contrary, Whoever has charge of the principal has charge of the accessory. Now priests are charged with the dispensation of the Eucharist to their subjects, to which sacrament the absolution of sins is subordinate [*Cf. Q, A, ad 1]. Therefore, as far as the power of the keys is concerned, a priest can absolve his subject from any sins whatever.
Further, grace, however small, removes all sin. But a priest dispenses sacraments whereby grace is given. Therefore, as far as the power of the keys is concerned, he can absolve from all sins.
I answer that, The power of order, considered in itself, extends to the remission of all sins. But since, as stated above, the use of this power requires jurisdiction which inferiors derive from their superiors, it follows that the superior can reserve certain matters to himself, the judgment of which he does not commit to his inferior; otherwise any simple priest who has jurisdiction can absolve from any sin. Now there are five cases in which a simple priest must refer his penitent to his superior. The first is when a public penance has to be imposed, because in that case the bishop is the proper minister of the sacrament. The second is the case of those who are excommunicated when the inferior priest cannot absolve a penitent through the latter being excommunicated by his superior. The third case is when he finds that an irregularity has been contracted, for the dispensation of which he has to have recourse to his superior. The fourth is the case of arson. The fifth is when it is the custom in a diocese for the more heinous crimes to be reserved to the bishop, in order to inspire fear, because custom in these cases either gives the power or takes it away.
Reply to Objection 1: In this case the priest should not hear the confession of his accomplice, with regard to that particular sin, but must refer her to another: nor should she confess to him but should ask permission to go to another, or should have recourse to his superior if he refused, both on account of the danger, and for the sake of less shame. If, however, he were to absolve her it would be valid*: because when Augustine says that they should not be guilty of the same sin, he is speaking of what is congruous, not of what is essential to the sacrament. [*Benedict XIV declared the absolution of an accomplice "in materia turpi" to be invalid.]
Reply to Objection 2: Penance delivers man from all defects of guilt, but not from all defects of punishment, since even after doing penance for murder, a man remains irregular. Hence a priest can absolve from a crime, but for the remission of the punishment he must refer the penitent to the superior, except in the case of excommunication, absolution from which should precede absolution from sin, for as long as a man is excommunicated, he cannot receive any sacrament of the Church.
Reply to Objection 3: This objection considers those cases in which superiors reserve the power of jurisdiction to themselves.
Objection 1: It would seem that a man cannot use the keys in respect of a superior. For every sacramental act requires its proper matter. Now the proper matter for the use of the keys, is a person who is subject, as stated above (Q, A). Therefore a priest cannot use the keys in respect of one who is not his subject.
Objection 2: Further, the Church Militant is an image of the Church Triumphant. Now in the heavenly Church an inferior angel never cleanses, enlightens or perfects a higher angel. Therefore neither can an inferior priest exercise on a superior a hierarchical action such as absolution.
Objection 3: Further, the judgment of Penance should be better regulated than the judgment of an external court. Now in the external court an inferior cannot excommunicate or absolve his superior. Therefore, seemingly, neither can he do so in the penitential court.
On the contrary, The higher prelate is also "compassed with infirmity," and may happen to sin. Now the power of the keys is the remedy for sin. Therefore, since he cannot use the key on himself, for he cannot be both judge and accused at the same time, it seems that an inferior can use the power of the keys on him.
Further, absolution which is given through the power of the keys, is ordained to the reception of the Eucharist. But an inferior can give Communion to his superior, if the latter asks him to. Therefore he can use the power of the keys on him if he submit to him.
I answer that, The power of the keys, considered in itself, is applicable to all, as stated above (A): and that a priest is unable to use the keys on some particular person is due to his power being limited to certain individuals. Therefore he who limited his power can extend it to whom he wills, so that he can give him power over himself, although he cannot use the power of the keys on himself, because this power requires to be exercised on a subject, and therefore on someone else, for no man can be subject to himself.
Reply to Objection 1: Although the bishop whom a simple priest absolves is his superior absolutely speaking, yet he is beneath him in so far as he submits himself as a sinner to him.
Reply to Objection 2: In the angels there can be no defect by reason of which the higher angel can submit to the lower, such as there can happen to be among men; and so there is no comparison.
Reply to Objection 3: External judgment is according to men, whereas the judgment of confession is according to God, in Whose sight a man is lessened by sinning, which is not the case in human prelacy. Therefore just as in external judgment no man can pass sentence of excommunication on himself, so neither can he empower another to excommunicate him. On the other hand, in the tribunal of conscience he can give another the power to absolve him, though he cannot use that power himself.
It may also be replied that absolution in the tribunal of the confessional belongs principally to the power of the keys and consequently to the power of jurisdiction, whereas excommunication regards jurisdiction exclusively. And, as to the power of orders, all are equal, but not as to jurisdiction. Wherefore there is no comparison.