Summa Theologica, by St. Thomas Aquinas, [1947], at sacred-texts.com
We must now consider the recipients of the sacrament of Penance: under which head there are three points of inquiry:
(1) Whether penance can be in the innocent?
(2) Whether it can be in the saints in glory?
(3) Whether in the good or bad angels?
Objection 1: It would seem that penance cannot be in the innocent. For penance consists in bewailing one's evil deeds: whereas the innocent have done no evil. Therefore penance cannot be in them.
Objection 2: Further, the very name of penance [poenitentia] implies punishment [poena]. But the innocent do not deserve punishment. Therefore penance is not in them.
Objection 3: Further, penance coincides with vindictive justice. But if all were innocent, there would be no room for vindictive justice. Therefore there would be no penance, so that there is none in the innocent.
On the contrary, All the virtues are infused together. But penance is a virtue. Since, therefore, other virtues are infused into the innocent at Baptism, penance is infused with them.
Further, a man is said to be curable though he has never been sick in body: therefore in like manner, one who has never been sick spiritually. Now even as there can be no actual cure from the wound of sin without an act of penance, so is there no possibility of cure without the habit of penance. Therefore one who has never had the disease of sin, has the habit of penance.
I answer that, Habit comes between power and act: and since the removal of what precedes entails the removal of what follows, but not conversely, the removal of the habit ensues from the removal of the power to act, but not from the removal of the act. And because removal of the matter entails the removal of the act, since there can be no act without the matter into which it passes, hence the habit of a virtue is possible in one for whom the matter is not available, for the reason that it can be available, so that the habit can proceed to its act---thus a poor man can have the habit of magnificence, but not the act, because he is not possessed of great wealth which is the matter of magnificence, but he can be possessed thereof.
Reply to Objection 1: Although the innocent have committed no sin, nevertheless they can, so that they are competent to have the habit of penance. Yet this habit can never proceed to its act, except perhaps with regard to their venial sins, because mortal sins destroy the habit. Nevertheless it is not without its purpose, because it is a perfection of the natural power.
Reply to Objection 2: Although they deserve no punishment actually, yet it is possible for something to be in them for which they would deserve to be punished.
Reply to Objection 3: So long as the power to sin remains, there would be room for vindictive justice as to the habit, though not as to the act, if there were no actual sins.
Objection 1: It would seem that the saints in glory have not penance. For, as Gregory says (Moral. iv), "the blessed remember their sins, even as we, without grief, remember our griefs after we have been healed." But penance is grief of the heart. Therefore the saints in heaven have not penance.
Objection 2: Further, the saints in heaven are conformed to Christ. But there was no penance in Christ, since there was no faith which is the principle of penance. Therefore there will be no penance in the saints in heaven.
Objection 3: Further, a habit is useless if it is not reduced to its act. But the saints in heaven will not repent actually, because, if they did, there would be something in them against their wish. Therefore the habit of penance will not be in them.
Objection 4: On the other hand, penance is a part of justice. But justice is "perpetual and immortal" (Wis. 1:15), and will remain in heaven. Therefore penance will also.
Objection 5: Further, we read in the Lives of the Fathers, that one of them said that even Abraham will repent of not having done more good. But one ought to repent of evil done more than of good left undone, and which one was not bound to do, for such is the good in question. Therefore repentance will be there of evil done.
I answer that, The cardinal virtues will remain in heaven, but only as regards the acts which they exercise in respect of their end. Wherefore, since the virtue of penance is a part of justice which is a cardinal virtue, whoever has the habit of penance in this life, will have it in the life to come: but he will not have the same act as now, but another, viz. thanksgiving to God for His mercy in pardoning his sins.
Reply to Objection 1: This argument proves that they do not have the same act as penance has now; and we grant this.
Reply to Objection 2: Christ could not sin, wherefore the matter of this virtue was lacking in His respect both actually and potentially: so that there is no comparison between Him and others.
Reply to Objection 3: Repentance, properly speaking, considered as that act of penance which is in this life, will not be in heaven: and yet the habit will not be without its use, for it will have another act.
Reply OBJ 4,5: We grant the Fourth argument. But since the Fifth Objection proves that there will be the same act of penance in heaven as now, we answer the latter by saying that in heaven one will be altogether conformed to the will of God. Wherefore, as God, by His antecedent will, but not by His consequent will, wishes that all things should be good, and therefore that there should be no evil, so is it with the blessed. It is this will that this holy father improperly calls penance.
Objection 1: It would seem that even a good or bad angel can be a subject of penance. For fear is the beginning of penance. But fear is in the angels, according to James 2:19: "The devils . . . believe and tremble." Therefore there can be penance in them.
Objection 2: Further, the Philosopher says (Ethic. ix, 4) that "evil men are full of repentance, and this is a great punishment for them." Now the devils are exceeding evil, nor is there any punishment that they lack. Therefore they can repent.
Objection 3: Further, a thing is more easily moved to that which is according to its nature than to that which is against its nature: thus water which has by violence been heated, of itself returns to its natural property. Now angels can be moved to sin which is contrary to their common nature. Much more therefore can they return to that which is in accord with their nature. But this is done by penance. Therefore they are susceptible to penance.
Objection 4: Further, what applies to angels, applies equally to separated souls, as Damascene says (De Fide Orth. ii, 4). But there can be penance in separated souls, as some say, as in the souls of the blessed in heaven. Therefore there can be penance in the angels.
On the contrary, By penance man obtains pardon for the sin he has committed. But this is impossible in the angels. Therefore they are not subjects of penance.
Further, Damascene says (De Fide Orth. ii, 4) that man is subject to penance on account of the weakness of his body. But the angels are not united to a body. Therefore no penance can be in them.
I answer that, In us, penance is taken in two senses; first, as a passion, and thus it is nothing but pain or sorrow on account of a sin committed: and though, as a passion it is only in the concupiscible part, yet, by way of comparison, the name of penance is given to that act of the will, whereby a man detests what he has done, even as love and other passions are spoken of as though they were in the intellectual appetite. Secondly, penance is taken as a virtue, and in this way its act consists in the detestation of evil done, together with the purpose of amendment and the intention of expiating the evil, or of placating God for the offense committed. Now detestation of evil befits a person according as he is naturally ordained to good. And since this order or inclination is not entirely destroyed in any creature, it remains even in the damned, and consequently the passion of repentance, or something like it, remains in them too, as stated in Wis. 5:3 "(saying) within themselves, repenting," etc. This repentance, as it is not a habit, but a passion or act, can by no means be in the blessed angels, who have not committed any sins: but it is in the wicked angels, since the same applies to them as to the lost souls, for, according to Damascene (De Fide Orth. ii, 4), "death is to men what sin is to an angel." But no forgiveness is possible for the sin of an angel. Now sin is the proper object of the virtue itself which we call penance, in so far as it can be pardoned or expiated. Therefore, since the wicked angels cannot have the matter, they have not the power to produce the act, so that neither can they have the habit. Hence the angels cannot be subjects of the virtue of penance.
Reply to Objection 1: A certain movement of penance is engendered in them from fear, but not such as is a virtue.
This suffices for the Reply to the Second Objection.
Reply to Objection 3: Whatever is natural in them is entirely good, and inclines to good: but their free-will is fixed on evil. And since the movement of virtue and vice follows the inclination, not of nature, but of the free-will, there is no need that there should be movements of virtue in them either actually or possibly, although they are inclined to good by nature.
Reply to Objection 4: There is no parity between the holy angels and the beatified souls, because in the latter there has been or could have been a sin that could be pardoned, but not in the former: so that though they are like as to their present state, they differ as to their previous states, which penance regards directly.