Summa Theologica, by St. Thomas Aquinas, , at sacred-texts.com
We must now consider the power of the ministers of this sacrament, which power depends on the keys. As to this matter, in the first place we shall treat of the keys, secondly, of excommunication, thirdly, of indulgences, since these two things are connected with the power of the keys. The first of these considerations will be fourfold: (1) the nature and meaning of the keys. (2) the use of the keys; (3) the ministers of the keys; (4) those on whom the use of the keys can be exercised.
Under the first head there are three points of inquiry:
(1) Whether there ought to be keys in the Church?
(2) Whether the key is the power of binding and loosing, etc.?
(3) Whether there are two keys or only one?
Objection 1: It would seem that there is no necessity for keys in the Church. For there is no need for keys that one may enter a house the door of which is open. But it is written (Apoc. 4:1): "I looked and behold a door was opened in heaven," which door is Christ, for He said of Himself (Jn. 10:7): "I am the door." Therefore the Church needs no keys for the entrance into heaven.
Objection 2: Further, a key is needed for opening and shutting. But this belongs to Christ alone, "Who openeth and no man shutteth, shutteth and no man openeth" (Apoc. 3:7). Therefore the Church has no keys in the hands of her ministers.
Objection 3: Further, hell is opened to whomever heaven is closed, and vice versa. Therefore whoever has the keys of heaven, has the keys of hell. But the Church is not said to have the keys of hell. Therefore neither has she the keys of heaven.
On the contrary, It is written (Mat. 16:19): "To thee will I give the keys of the kingdom of heaven."
Further, every dispenser should have the keys of the things that he dispenses. But the ministers of the Church are the dispensers of the divine mysteries, as appears from 1 Cor. 4:1. Therefore they ought to have the keys.
I answer that, In material things a key is an instrument for opening a door. Now the door of the kingdom is closed to us through sin, both as to the stain and as to the debt of punishment. Wherefore the power of removing this obstacle is called a key. Now this power is in the Divine Trinity by authority; hence some say that God has the key of "authority." But Christ Man had the power to remove the above obstacle, through the merit of His Passion, which also is said to open the door; hence some say that He has the keys of "excellence." And since "the sacraments of which the Church is built, flowed from the side of Christ while He lay asleep on the cross" [*Augustine, Enarr. in Ps. 138], the efficacy of the Passion abides in the sacraments of the Church. Wherefore a certain power for the removal of the aforesaid obstacle is bestowed on the ministers of the Church, who are the dispensers of the sacraments, not by their own, but by a Divine power and by the Passion of Christ. This power is called metaphorically the Church's key, and is the key of "ministry."
Reply to Objection 1: The door of heaven, considered in itself, is ever open, but it is said to be closed to someone, on account of some obstacle against entering therein, which is in himself. The obstacle which the entire human nature inherited from the sin of the first man was removed by Christ's Passion; hence, after the Passion, John saw an opened door in heaven. Yet that door still remains closed to this or that man, on account of the original sin which he has contracted, or the actual sin which he has committed: hence we need the sacraments and the keys of the Church.
Reply to Objection 2: This refers to His closing Limbo, so that thenceforth no one should go there, and to His opening of Paradise, the obstacle of nature being removed by His Passion.
Reply to Objection 3: The key whereby hell is opened and closed, is the power of bestowing grace, whereby hell is opened to man, so that he is taken out from sin which is the door of hell, and closed, so that by the help of grace man should no more fall into sin. Now the power of bestowing grace belongs to God alone, wherefore He kept this key to Himself. But the key of the kingdom is also the power to remit the debt of temporal punishment, which debt prevents man from entering the kingdom Consequently the key of the kingdom can be given to man rather than the key of hell, for they are not the same, as is clear from what has been said. For a man may be set free from hell by the remission of the debt of eternal punishment, without being at once admitted to the kingdom, on account of his yet owing a debt of temporal punishment.
It may also be replied, as some state, that the key of heaven is also the key of hell, since if one is opened to a man, the other, for that very reason, is closed to him, but it takes its name from the better of the two.
Objection 1: It would seem that the key is not the power of binding and loosing, whereby "the ecclesiastical judge has to admit the worthy to the kingdom and exclude the unworthy" therefrom, as stated in the text (Sent. iv, D, 16). For the spiritual power conferred in a sacrament is the same as the character. But the key and the character do not seem to be the same, since by the character man is referred to God, whereas by the key he is referred to his subjects. Therefore the key is not a power.
Objection 2: Further, an ecclesiastical judge is only one who has jurisdiction, which is not given at the same time as orders. But the keys are given in the conferring of orders. Therefore there should have been no mention of the ecclesiastical judge in the definition of the keys.
Objection 3: Further, when a man has something of himself, he needs not to be reduced to act by some active power. Now a man is admitted to the kingdom from the very fact that he is worthy. Therefore it does not concern the power of the keys to admit the worthy to the kingdom.
Objection 4: Further, sinners are unworthy of the kingdom. But the Church prays for sinners, that they may go to heaven. Therefore she does not exclude the unworthy, but admits them, so far as she is concerned.
Objection 5: Further, in every ordered series of agents, the last end belongs to the principal and not to the instrumental agent. But the principal agent in view of man's salvation is God. Therefore admission to the kingdom, which is the last end, belongs to Him, and not to those who have the keys, who are as instrumental or ministerial agents.
I answer that, According to the Philosopher (De Anima ii, text. 33), "powers are defined from their acts." Wherefore, since the key is a kind of power, it should be defined from its act or use, and reference to the act should include its object from which it takes its species, and the mode of acting whereby the power is shown to be well-ordered. Now the act of the spiritual power is to open heaven, not absolutely, since it is already open, as stated above (A, ad 1), but for this or that man; and this cannot be done in an orderly manner without due consideration of the worthiness of the one to be admitted to heaven. Hence the aforesaid definition of the key gives the genus, viz. "power," the subject of the power, viz. the "ecclesiastical judge," and the act, viz. "of excluding or admitting," corresponding to the two acts of a material key which are to open and shut; the object of which act is referred to in the words "from the kingdom," and the mode, in the words, "worthy" and "unworthy," because account is taken of the worthiness or unworthiness of those on whom the act is exercised.
Reply to Objection 1: The same power is directed to two things, of which one is the cause of the other, as heat, in fire, is directed to make a thing hot and to melt it. And since every grace and remission in a mystical body comes to it from its head, it seems that it is essentially the same power whereby a priest can consecrate, and whereby he can loose and bind, if he has jurisdiction, and that there is only a logical difference, according as it is referred to different effects, even as fire in one respect is said to have the power of heating, and in another, the power of melting. And because the character of the priestly order is nothing else than the power of exercising that act to which the priestly order is chiefly ordained (if we maintain that it is the same as a spiritual power), therefore the character, the power of consecrating, and the power of the keys are one and the same essentially, but differ logically.
Reply to Objection 2: All spiritual power is conferred by some kind of consecration. Therefore the key is given together with the order: yet the use of the key requires due matter, i.e. a people subject through jurisdiction, so that until he has jurisdiction, the priest has the keys, but he cannot exercise the act of the keys. And since the key is defined from its act, its definition contains a reference to jurisdiction.
Reply to Objection 3: A person may be worthy to have something in two ways, either so as to have a right to possess it, and thus whoever is worthy has heaven already opened to him---or so that it is meet that he should receive it, and thus the power of the keys admits those who are worthy, but to whom heaven is not yet altogether opened.
Reply to Objection 4: Even as God hardens not by imparting malice, but by withholding grace, so a priest is said to exclude, not as though he placed an obstacle to entrance, but because he does not remove an obstacle which is there, since he cannot remove it unless God has already removed it. [*St. Thomas here follows the opinion of Peter Lombard, and replies in the negative. Later in life he altered his opinion. Cf. TP, Q, A; TP, Q, A; TP, Q, A.] Hence God is prayed that He may absolve, so that there may be room for the priest's absolution.
Reply to Objection 5: The priest's act does not bear immediately on the kingdom, but on the sacraments, by means of which man wins to the kingdom.
Objection 1: It would seem that there are not two keys but only one. For one lock requires but one key. Now the lock for the removal of which the keys of the Church are required, is sin. Therefore the Church does not require two keys for one sin.
Objection 2: Further, the keys are given when orders are conferred. But knowledge is not always due to infusion, but sometimes is acquired, nor is it possessed by all those who are ordained, and is possessed by some who are not ordained. Therefore knowledge is not a key, so that there is but one key, viz. the power of judging.
Objection 3: Further, the power which the priest has over the mystic body of Christ flows from the power which he has over Christ's true body. Now the power of consecrating Christ's true body is but one. Therefore the power which regards Christ's mystic body is but one. But this is a key. Therefore, etc.
Objection 4: On the other hand, It seems that there are more than two keys. For just as knowledge and power are requisite for man to act, so is will. But the knowledge of discretion is reckoned as a key, and so is the power of judging. Therefore the will to absolve should be counted as a key.
Objection 5: Further, all three Divine Persons remit sins. Now the priest, through the keys, is the minister for the remission of sins. Therefore he should have three keys, so that he may be conformed to the Trinity.
I answer that, Whenever an act requires fitness on the part of the recipient, two things are necessary in the one who has to perform the act, viz. judgment of the fitness of the recipient, and accomplishment of the act. Therefore in the act of justice whereby a man is given what he deserves, there needs to be a judgment in order to discern whether he deserves to receive. Again, an authority or power is necessary for both these things, for we cannot give save what we have in our power; nor can there be judgment, without the right to enforce it, since judgment is determined to one particular thing, which determination it derives, in speculative matters, from the first principles which cannot be gainsaid, and, in practical matters, from the power of command vested in the one who judges. And since the act of the key requires fitness in the person on whom it is exercised---because the ecclesiastical judge, by means of the key, "admits the worthy and excludes the unworthy," as may be seen from the definition given above (A)---therefore the judge requires both judgment of discretion whereby he judges a man to be worthy, and also the very act of receiving (that man's confession); and for both these things a certain power or authority is necessary. Accordingly we may distinguish two keys, the first of which regards the judgment about the worthiness of the person to be absolved, while the other regards the absolution.
These two keys are distinct, not in the essence of authority, since both belong to the minister by virtue of his office, but in comparison with their respective acts, one of which presupposes the other.
Reply to Objection 1: One key is ordained immediately to the opening of one lock, but it is not unfitting that one key should be ordained to the act of another. Thus it is in the case in point. For it is the second key, which is the power of binding and loosing, that opens the lock of sin immediately, but the key of knowledge shows to whom that lock should be opened.
Reply to Objection 2: There are two opinions about the key of knowledge. For some say that knowledge considered as a habit, acquired or infused, is the key in this case, and that it is not the principal key, but is called a key through being subordinate to another key: so that it is not called a key when the other key is wanting, for instance, in an educated man who is not a priest. And although priests lack this key at times, through being without knowledge, acquired or infused, of loosing and binding, yet sometimes they make use of their natural endeavors, which they who hold this opinion call a little key, so that although knowledge be not bestowed together with orders, yet with the conferring of orders the knowledge becomes a key which it was not before. This seems to have been the opinion of the Master (Sent. iv, D, 19).
But this does not seem to agree with the words of the Gospel, whereby the keys are promised to Peter (Mat. 16:19), so that not only one but two are given in orders. For which reason the other opinion holds that the key is not knowledge considered as a habit, but the authority to exercise the act of knowledge, which authority is sometimes without knowledge, while the knowledge is sometimes present without the authority. This may be seen even in secular courts, for a secular judge may have the authority to judge, without having the knowledge of the law, while another man, on the contrary, has knowledge of the law without having the authority to judge. And since the act of judging to which a man is bound through the authority which is vested in him, and not through his habit of knowledge, cannot be well performed without both of the above, the authority to judge, which is the key of knowledge, cannot be accepted without sin by one who lacks knowledge; whereas knowledge void of authority can be possessed without sin.
Reply to Objection 3: The power of consecrating is directed to only one act of another kind, wherefore it is not numbered among the keys, nor is it multiplied as the power of the keys, which is directed to different acts, although as to the essence of power and authority it is but one, as stated above.
Reply to Objection 4: Everyone is free to will, so that no one needs authority to will; wherefore will is not reckoned as a key.
Reply to Objection 5: All three Persons remit sins in the same way as one Person, wherefore there is no need for the priest, who is the minister of the Trinity, to have three keys: and all the more, since the will, which is appropriated to the Holy Ghost, requires no key, as stated above (ad 4).