Summa Th. III EN Qu.85 a.2

Whether Penance is a special virtue?

Objection: 1. It would seem that penance is not a special virtue. For it seems that to rejoice at the good one has done, and to grieve for the evil one has done are acts of the same nature. But joy for the good one has done is not a special virtue, but is a praiseworthy emotion proceeding from charity, as Augustine states (De Civ. Dei xiv, 7,8,9): wherefore the Apostle says (1Co 13,6) that charity "rejoiceth not at iniquity, but rejoiceth with the truth." Therefore, in like manner, neither is penance, which is sorrow for past sins, a special virtue, but an emotion resulting from charity.
2. Further, every special virtue has its special matter, because habits are distinguished by their acts, and acts by their objects. But penance has no special matter, because its matter is past sins in any matter whatever. Therefore penance is not a special virtue.
3. Further, nothing is removed except by its contrary. But penance removes all sins. Therefore it is contrary to all sins, and consequently is not a special virtue.

On the contrary The Law has a special precept about penance, as stated above (Question [84], Articles [5],7).
I answer that As stated in the I-II 54,1, ad 1, I-II 54,2, habits are specifically distinguished according to the species of their acts, so that whenever an act has a special reason for being praiseworthy, there must needs be a special habit. Now it is evident that there is a special reason for praising the act of penance, because it aims at the destruction of past sin, considered as an offense against God, which does not apply to any other virtue. We must therefore conclude that penance is a special virtue.

Reply to Objection: 1. An act springs from charity in two ways: first as being elicited by charity, and a like virtuous act requires no other virtue than charity, e.g. to love the good, to rejoice therein, and to grieve for what is opposed to it. Secondly, an act springs from charity, being, so to speak, commanded by charity; and thus, since charity commands all the virtues, inasmuch as it directs them to its own end, an act springing from charity may belong even to another special virtue. Accordingly, if in the act of the penitent we consider the mere displeasure in the past sin, it belongs to charity immediately, in the same way as joy for past good acts; but the intention to aim at the destruction of past sin requires a special virtue subordinate to charity.
2. In point of fact, penance has indeed a general matter, inasmuch as it regards all sins; but it does so under a special aspect, inasmuch as they can be remedied by an act of man in co-operating with God for his justification.
3. Every special virtue removes formally the habit of the opposite vice, just as whiteness removes blackness from the same subject: but penance removes every sin effectively, inasmuch as it works for the destruction of sins, according as they are pardonable through the grace of God if man co-operate therewith. Wherefore it does not follow that it is a general virtue.

Whether the virtue of penance is a species of justice?

Objection: 1. It would seem that the virtue of penance is not a species of justice. For justice is not a theological but a moral virtue, as was shown in the II-II 62,3. But penance seems to be a theological virtue, since God is its object, for it makes satisfaction to God, to Whom, moreover, it reconciles the sinner. Therefore it seems that penance is not a species of justice.
2. Further, since justice is a moral virtue it observes the mean. Now penance does not observe the mean, but rather goes to the extreme, according to Jr 6,26: "Make thee mourning as for an only son, a bitter lamentation." Therefore penance is not a species of justice.
3. Further, there are two species of justice, as stated in Ethic. v, 4, viz. "distributive" and "commutative." But penance does not seem to be contained under either of them. Therefore it seems that penance is not a species of justice.
4. Further, a gloss on Lc 6,21, "Blessed are ye that weep now," says: "It is prudence that teaches us the unhappiness of earthly things and the happiness of heavenly things." But weeping is an act of penance. Therefore penance is a species of prudence rather than of justice.

On the contrary Augustine says in De Poenitentia [*De vera et falsa Poenitentia, the authorship of which is unknown]: "Penance is the vengeance of the sorrowful, ever punishing in them what they are sorry for having done." But to take vengeance is an act of justice, wherefore Tully says (De Inv. Rhet. ii) that one kind of justice is called vindictive. Therefore it seems that penance is a species of justice.
I answer that As stated above (Article [1], ad 2) penance is a special virtue not merely because it sorrows for evil done (since charity would suffice for that), but also because the penitent grieves for the sin he has committed, inasmuch as it is an offense against God, and purposes to amend. Now amendment for an offense committed against anyone is not made by merely ceasing to offend, but it is necessary to make some kind of compensation, which obtains in offenses committed against another, just as retribution does, only that compensation is on the part of the offender, as when he makes satisfaction, whereas retribution is on the part of the person offended against. Each of these belongs to the matter of justice, because each is a kind of commutation. Wherefore it is evident that penance, as a virtue, is a part of justice.It must be observed, however, that according to the Philosopher (Ethic. v, 6) a thing is said to be just in two ways, simply and relatively. A thing is just simply when it is between equals, since justice is a kind of equality, and he calls this the politic or civil just, because all citizens are equal, in the point of being immediately under the ruler, retaining their freedom. But a thing is just relatively when it is between parties of whom one is subject to the other, as a servant under his master, a son under his father, a wife under her husband. It is this kind of just that we consider in penance. Wherefore the penitent has recourse to God with a purpose of amendment, as a servant to his master, according to Ps 122,2: "Behold, as the eyes of servants are on the hands of their masters . . . so are our eyes unto the Lord our God, until He have mercy on us"; and as a son to his father, according to Lc 15,21: "Father, I have sinned against heaven and before thee"; and as a wife to her husband, according to Jr 3,1: "Thou hast prostituted thyself to many lovers; nevertheless return to Me, saith the Lord."

Reply to Objection: 1. As stated in Ethic. v, 1, justice is a virtue towards another person, and the matter of justice is not so much the person to whom justice is due as the thing which is the subject of distribution or commutation. Hence the matter of penance is not God, but human acts, whereby God is offended or appeased; whereas God is as one to whom justice is due. Wherefore it is evident that penance is not a theological virtue, because God is not its matter or object.
2. The mean of justice is the equality that is established between those between whom justice is, as stated in Ethic. v. But in certain cases perfect equality cannot be established, on account of the excellence of one, as between father and son, God and man, as the Philosopher states (Ethic. viii, 14), wherefore in such cases, he that falls short of the other must do whatever he can. Yet this will not be sufficient simply, but only according to the acceptance of the higher one; and this is what is meant by ascribing excess to penance.
3. As there is a kind of commutation in favors, when, to wit, a man gives thanks for a favor received, so also is there commutation in the matter of offenses, when, on account of an offense committed against another, a man is either punished against his will, which pertains to vindictive justice, or makes amends of his own accord, which belongs to penance, which regards the person of the sinner, just as vindictive justice regards the person of the judge. Therefore it is evident that both are comprised under commutative justice.
4. Although penance is directly a species of justice, yet, in a fashion, it comprises things pertaining to all the virtues; for inasmuch as there is a justice of man towards God, it must have a share in matter pertaining to the theological virtues, the object of which is God. Consequently penance comprises faith in Christ's Passion, whereby we are cleansed of our sins, hope for pardon, and hatred of vice, which pertains to charity. Inasmuch as it is a moral virtue, it has a share of prudence, which directs all the moral virtues: but from the very nature of justice, it has not only something belonging to justice, but also something belonging to temperance and fortitude, inasmuch as those things which cause pleasure, and which pertain to temperance, and those which cause terror, which fortitude moderates, are objects of commutative justice. Accordingly it belongs to justice both to abstain from pleasure, which belongs to temperance, and to bear with hardships, which belongs to fortitude.

Whether the will is properly the subject of penance?

Objection: 1. It would seem that the subject of penance is not properly the will. For penance is a species of sorrow. But sorrow is in the concupiscible part, even as joy is. Therefore penance is in the concupiscible faculty.
2. Further, penance is a kind of vengeance, as Augustine states in De Poenitentia [*De vera et falsa Poenitentia, the authorship of which is unknown]. But vengeance seems to regard the irascible faculty, since anger is the desire for vengeance. Therefore it seems that penance is in the irascible part.
3. Further, the past is the proper object of the memory, according to the Philosopher (De Memoria i). Now penance regards the past, as stated above (Article [1], ad 2, ad 3). Therefore penance is subjected in the memory.
4. Further, nothing acts where it is not. Now penance removes sin from all the powers of the soul. Therefore penance is in every power of the soul, and not only in the will.

On the contrary Penance is a kind of sacrifice, according to Ps 50,19: "A sacrifice to God is an afflicted spirit." But to offer a sacrifice is an act of the will, according to Ps 53,8: "I will freely sacrifice to Thee." Therefore penance is in the will.
I answer that We can speak of penance in two ways: first, in so far as it is a passion, and thus, since it is a kind of sorrow, it is in the concupiscible part as its subject; secondly, in so far as it is a virtue, and thus, as stated above (Article [3]), it is a species of justice. Now justice, as stated in the I-II 56,6, is subjected in the rational appetite which is the will. Therefore it is evident that penance, in so far as it is a virtue, is subjected in the will, and its proper act is the purpose of amending what was committed against God.

Reply to Objection: 1. This argument considers penance as a passion.
2. To desire vengeance on another, through passion, belongs to the irascible appetite, but to desire or take vengeance on oneself or on another, through reason, belongs to the will.
3. The memory is a power that apprehends the past. But penance belongs not to the apprehensive but to the appetitive power, which presupposes an act of the apprehension. Wherefore penance is not in the memory, but presupposes it.
4. The will, as stated above (I 82,4 I ; I-II 9,1), moves all the other powers of the soul; so that it is not unreasonable for penance to be subjected in the will, and to produce an effect in each power of the soul.

Whether penance originates from fear?

Objection: 1. It would seem that penance does not originate from fear. For penance originates in displeasure at sin. But this belongs to charity, as stated above (Article [3]). Therefore penance originates from love rather than fear.
2. Further, men are induced to do penance, through the expectation of the heavenly kingdom, according to Mt 3,2 and Mt 4,17: "Do penance, for the kingdom of heaven is at hand." Now the kingdom of heaven is the object of hope. Therefore penance results from hope rather than from fear.
3. Further, fear is an internal act of man. But penance does not seem to arise in us through any work of man, but through the operation of God, according to Jr 31,19: "After Thou didst convert me I did penance." Therefore penance does not result from fear.

On the contrary It is written (Is 26,17): "As a woman with child, when she draweth near the time of her delivery, is in pain, and crieth out in her pangs, so ere we become," by penance, to wit; and according to another [*The Septuagint] version the text continues: "Through fear of Thee, O Lord, we have conceived, and been as it were in labor, and have brought forth the spirit of salvation," i.e. of salutary penance, as is clear from what precedes. Therefore penance results from fear.
I answer that We may speak of penance in two ways: first, as to the habit, and then it is infused by God immediately without our operating as principal agents, but not without our co-operating dispositively by certain acts. Secondly, we may speak of penance, with regard to the acts whereby in penance we co-operate with God operating, the first principle [*Cf. I-II 113,0] of which acts is the operation of God in turning the heart, according to Lam. 5:21: "Convert us, O Lord, to Thee, and we shall be converted"; the second, an act of faith; the third, a movement of servile fear, whereby a man is withdrawn from sin through fear of punishment; the fourth, a movement of hope, whereby a man makes a purpose of amendment, in the hope of obtaining pardon; the fifth, a movement of charity, whereby sin is displeasing to man for its own sake and no longer for the sake of the punishment; the sixth, a movement of filial fear whereby a man, of his own accord, offers to make amends to God through fear of Him.Accordingly it is evident that the act of penance results from servile fear as from the first movement of the appetite in this direction and from filial fear as from its immediate and proper principle.

Reply to Objection: 1. Sin begins to displease a man, especially a sinner, on account of the punishments which servile fear regards, before it displeases him on account of its being an offense against God, or on account of its wickedness, which pertains to charity.
2. When the kingdom of heaven is said to be at hand, we are to understand that the king is on his way, not only to reward but also to punish. Wherefore John the Baptist said (Mt 3,7): "Ye brood of vipers, who hath showed you to flee from the wrath to come?"
3. Even the movement of fear proceeds from God's act in turning the heart; wherefore it is written (Dt 5,29): "Who shall give them to have such a mind, to fear Me?" And so the fact that penance results from fear does not hinder its resulting from the act of God in turning the heart.

Whether penance is the first of the virtues?

Objection: 1. It would seem that penance is the first of the virtues. Because, on Mt 3,2, "Do penance," etc., a gloss says: "The first virtue is to destroy the old man, and hate sin by means of penance."
2. Further, withdrawal from one extreme seems to precede approach to the other. Now all the other virtues seem to regard approach to a term, because they all direct man to do good; whereas penance seems to direct him to withdraw from evil. Therefore it seems that penance precedes all the other virtues.
3. Further, before penance, there is sin in the soul. Now no virtue is compatible with sin in the soul. Therefore no virtue precedes penance, which is itself the first of all and opens the door to the others by expelling sin.

On the contrary Penance results from faith, hope, and charity, as already stated (Articles [2],5). Therefore penance is not the first of the virtues.
I answer that In speaking of the virtues, we do not consider the order of time with regard to the habits, because, since the virtues are connected with one another, as stated in the I-II 65,1, they all begin at the same time to be in the soul; but one is said to precede the other in the order of nature, which order depends on the order of their acts, in so far as the act of one virtue presupposes the act of another. Accordingly, then, one must say that, even in the order of time, certain praiseworthy acts can precede the act and the habit of penance, e.g. acts of dead faith and hope, and an act of servile fear; while the act and habit of charity are, in point of time, simultaneous with the act and habit of penance, and with the habits of the other virtues. For, as was stated in the I-II 113,7 I-II 113,8, in the justification of the ungodly, the movement of the free-will towards God, which is an act of faith quickened by charity, and the movement of the free-will towards sin, which is the act of penance, are simultaneous. Yet of these two acts, the former naturally precedes the latter, because the act of the virtue of penance is directed against sin, through love of God; where the first-mentioned act is the reason and cause of the second.Consequently penance is not simply the first of the virtues, either in the order of time, or in the order of nature, because, in the order of nature, the theological virtues precede it simply. Nevertheless, in a certain respect, it is the first of the other virtues in the order of time, as regards its act, because this act is the first in the justification of the ungodly; whereas in the order of nature, the other virtues seem to precede, as that which is natural precedes that which is accidental; because the other virtues seem to be necessary for man's good, by reason of their very nature, whereas penance is only necessary if something, viz. sin, be presupposed, as stated above (Question [55], Article [2]), when we spoke of the relation of the sacrament of penance to the other sacraments aforesaid.

Reply to Objection: 1. This gloss is to be taken as meaning that the act of penance is the first in point of time, in comparison with the acts of the other virtues.
2. In successive movements withdrawal from one extreme precedes approach to the other, in point of time; and also in the order of nature, if we consider the subject, i.e. the order of the material cause; but if we consider the order of the efficient and final causes, approach to the end is first, for it is this that the efficient cause intends first of all: and it is this order which we consider chiefly in the acts of the soul, as stated in Phys. ii.
3. Penance opens the door to the other virtues, because it expels sin by the virtues of faith, hope and charity, which precede it in the order of nature; yet it so opens the door to them that they enter at the same time as it: because, in the justification of the ungodly, at the same time as the free-will is moved towards God and against sin, the sin is pardoned and grace infused, and with grace all the virtues, as stated in the I-II 65,3 I-II 63,5.


We must now consider the effect of Penance; and (1) as regards the pardon of mortal sins; (2) as regards the pardon of venial sins; (3) as regards the return of sins which have been pardoned; (4) as regards the recovery of the virtues.

Under the first head there are six points of inquiry:

(1) Whether all mortal sins are taken away by Penance?

(2) Whether they can be taken away without Penance?

(3) Whether one can be taken away without the other?

(4) Whether Penance takes away the guilt while the debt remains?

(5) Whether any remnants of sin remain?

(6) Whether the removal of sin is the effect of Penance as a virtue, or as a sacrament?

Whether all sins are taken away by Penance?

Objection: 1. It would seem that not all sins are taken away by Penance. For the Apostle says (He 12,17) that Esau "found no place of repentance, although with tears he had sought it," which a gloss explains as meaning that "he found no place of pardon and blessing through Penance": and it is related (2M 9,13) of Antiochus, that "this wicked man prayed to the Lord, of Whom he was not to obtain mercy." Therefore it does not seem that all sins are taken away by Penance.
2. Further, Augustine says (De Serm. Dom. in Monte i) that "so great is the stain of that sin (namely, when a man, after coming to the knowledge of God through the grace of Christ, resists fraternal charity, and by the brands of envy combats grace itself) that he is unable to humble himself in prayer, although he is forced by his wicked conscience to acknowledge and confess his sin." Therefore not every sin can be taken away by Penance.
3. Further, our Lord said (Mt 12,32): "He that shall speak against the Holy Ghost, it shall not be forgiven him, neither in this world nor in the world to come." Therefore not every sin can be pardoned through Penance.

On the contrary It is written (Ez 18,22): "I will not remember" any more "all his iniquities that he hath done."
I answer that The fact that a sin cannot be taken away by Penance may happen in two ways: first, because of the impossibility of repenting of sin; secondly, because of Penance being unable to blot out a sin. In the first way the sins of the demons and of men who are lost, cannot be blotted out by Penance, because their will is confirmed in evil, so that sin cannot displease them as to its guilt, but only as to the punishment which they suffer, by reason of which they have a kind of repentance, which yet is fruitless, according to Sg 5,3: "Repenting, and groaning for anguish of spirit." Consequently such Penance brings no hope of pardon, but only despair. Nevertheless no sin of a wayfarer can be such as that, because his will is flexible to good and evil. Wherefore to say that in this life there is any sin of which one cannot repent, is erroneous, first, because this would destroy free-will, secondly, because this would be derogatory to the power of grace, whereby the heart of any sinner whatsoever can be moved to repent, according to Pr 21,1: "The heart of the king is in the hand of the Lord: whithersoever He will He shall turn it."It is also erroneous to say that any sin cannot be pardoned through true Penance. First, because this is contrary to Divine mercy, of which it is written (Joel 2:13) that God is "gracious and merciful, patient, and rich in mercy, and ready to repent of the evil"; for, in a manner, God would be overcome by man, if man wished a sin to be blotted out, which God were unwilling to blot out. Secondly, because this would be derogatory to the power of Christ's Passion, through which Penance produces its effect, as do the other sacraments, since it is written (1Jn 2,2): "He is the propitiation for our sins, and not for ours only, but also for those of the whole world."Therefore we must say simply that, in this life, every sin can be blotted out by true Penance.

Reply to Objection: 1. Esau did not truly repent. This is evident from his saying (Gn 27,41): "The days will come of the mourning of my father, and I will kill my brother Jacob." Likewise neither did Antiochus repent truly; since he grieved for his past sin, not because he had offended God thereby, but on account of the sickness which he suffered in his body.
2. These words of Augustine should be understood thus: "So great is the stain of that sin, that man is unable to humble himself in prayer," i.e. it is not easy for him to do so; in which sense we say that a man cannot be healed, when it is difficult to heal him. Yet this is possible by the power of God's grace, which sometimes turns men even "into the depths of the sea" (Ps 67,23).
3. The word or blasphemy spoken against the Holy Ghost is final impenitence, as Augustine states (De Verb. Dom. xi), which is altogether unpardonable, because after this life is ended, there is no pardon of sins. or, if by the blasphemy against the Holy Ghost, we understand sin committed through certain malice, this means either that the blasphemy itself against the Holy Ghost is unpardonable, i.e. not easily pardonable, or that such a sin does not contain in itself any motive for pardon, or that for such a sin a man is punished both in this and in the next world, as we explained in the II-II 14,3.

Whether sin can be pardoned without Penance?

Objection: 1. It would seem that sin can be pardoned without Penance. For the power of God is no less with regard to adults than with regard to children. But He pardons the sins of children without Penance. Therefore He also pardons adults without penance.
2. Further, God did not bind His power to the sacraments. But Penance is a sacrament. Therefore by God's power sin can be pardoned without Penance.
3. Further, God's mercy is greater than man's. Now man sometimes forgives another for offending him, without his repenting: wherefore our Lord commanded us (Mt 5,44): "Love your enemies, do good to them that hate you." Much more, therefore, does God pardon men for offending him, without their repenting.

On the contrary The Lord said (Jr 18,8): "If that nation . . . shall repent of their evil" which they have done, "I also will repent of the evil that I have thought to do them," so that, on the other hand, if man "do not penance," it seems that God will not pardon him his sin.
I answer that It is impossible for a mortal actual sin to be pardoned without penance, if we speak of penance as a virtue. For, as sin is an offense against God, He pardons sin in the same way as he pardons an offense committed against Him. Now an offense is directly opposed to grace, since one man is said to be offended with another, because he excludes him from his grace. Now, as stated in the I-II 110,1, the difference between the grace of God and the grace of man, is that the latter does not cause, but presupposes true or apparent goodness in him who is graced, whereas the grace of God causes goodness in the man who is graced, because the good-will of God, which is denoted by the word "grace," is the cause of all created good. Hence it is possible for a man to pardon an offense, for which he is offended with someone, without any change in the latter's will; but it is impossible that God pardon a man for an offense, without his will being changed. Now the offense of mortal sin is due to man's will being turned away from God, through being turned to some mutable good. Consequently, for the pardon of this offense against God, it is necessary for man's will to be so changed as to turn to God and to renounce having turned to something else in the aforesaid manner, together with a purpose of amendment; all of which belongs to the nature of penance as a virtue. Therefore it is impossible for a sin to be pardoned anyone without penance as a virtue.But the sacrament of Penance, as stated above (Question [88], Article [3]), is perfected by the priestly office of binding and loosing, without which God can forgive sins, even as Christ pardoned the adulterous woman, as related in Jn 8, and the woman that was a sinner, as related in Luke vii, whose sins, however, He did not forgive without the virtue of penance: for as Gregory states (Hom. xxxiii in Evang.), "He drew inwardly by grace," i.e. by penance, "her whom He received outwardly by His mercy."

Reply to Objection: 1. In children there is none but original sin, which consists, not in an actual disorder of the will, but in a habitual disorder of nature, as explained in the I-II 82,1, and so in them the forgiveness of sin is accompanied by a habitual change resulting from the infusion of grace and virtues, but not by an actual change. On the other hand, in the case of an adult, in whom there are actual sins, which consist in an actual disorder of the will, there is no remission of sins, even in Baptism, without an actual change of the will, which is the effect of Penance.
2. This argument takes Penance as a sacrament.
3. God's mercy is more powerful than man's, in that it moves man's will to repent, which man's mercy cannot do.

Whether by Penance one sin can be pardoned without another?

Objection: 1. It would seem that by Penance one sin can be pardoned without another. For it is written (Amos 4:7): "I caused it to rain upon one city, and caused it not to rain upon another city; one piece was rained upon: and the piece whereupon I rained not, withered." These words are expounded by Gregory, who says (Hom. x super Ezech.): "When a man who hates his neighbor, breaks himself of other vices, rain falls on one part of the city, leaving the other part withered, for there are some men who, when they prune some vices, become much more rooted in others." Therefore one sin can be forgiven by Penance, without another.
2. Further, Ambrose in commenting on Ps 118, "Blessed are the undefiled in the way," after expounding verse 136 ("My eyes have sent forth springs of water"), says that "the first consolation is that God is mindful to have mercy; and the second, that He punishes, for although faith be wanting, punishment makes satisfaction and raises us up." Therefore a man can be raised up from one sin, while the sin of unbelief remains.
3. Further, when several things are not necessarily together, one can be removed without the other. Now it was stated in the I-II 73,1 that sins are not connected together, so that one sin can be without another. Therefore also one sin can be taken away by Penance without another being taken away.
4. Further, sins are the debts, for which we pray for pardon when we say in the Lord's Prayer: "Forgive us our trespasses," etc. Now man sometimes forgives one debt without forgiving another. Therefore God also, by Penance, forgives one sin without another.
5. Further, man's sins are forgiven him through the love of God, according to Jr 31,3: "I have loved thee with an everlasting love, therefore have I drawn thee, taking pity on thee." Now there is nothing to hinder God from loving a man in one respect, while being offended with him in another, even as He loves the sinner as regards his nature, while hating him for his sin. Therefore it seems possible for God, by Penance, to pardon one sin without another.

On the contrary Augustine says in De Poenitentia [*De vera et falsa Poenitentia, the authorship of which is unknown]: "There are many who repent having sinned, but not completely; for they except certain things which give them pleasure, forgetting that our Lord delivered from the devil the man who was both dumb and deaf, whereby He shows us that we are never healed unless it be from all sins."
I answer that It is impossible for Penance to take one sin away without another. First because sin is taken away by grace removing the offense against God. Wherefore it was stated in the I-II 109,7; I-II 113,2 that without grace no sin can be forgiven. Now every mortal sin is opposed to grace and excludes it. Therefore it is impossible for one sin to be pardoned without another. Secondly, because, as shown above (Article [2]) mortal sin cannot be forgiven without true Penance, to which it belongs to renounce sin, by reason of its being against God, which is common to all mortal sins: and where the same reason applies, the result will be the same. Consequently a man cannot be truly penitent, if he repent of one sin and not of another. For if one particular sin were displeasing to him, because it is against the love of God above all things (which motive is necessary for true repentance), it follows that he would repent of all. Whence it follows that it is impossible for one sin to be pardoned through Penance, without another. Thirdly, because this would be contrary to the perfection of God's mercy, since His works are perfect, as stated in Dt 32,4; wherefore whomsoever He pardons, He pardons altogether. Hence Augustine says [*De vera et falsa Poenitentia, the authorship of which is unknown], that "it is irreverent and heretical to expect half a pardon from Him Who is just and justice itself."

Reply to Objection: 1. These words of Gregory do not refer to the forgiveness of the guilt, but to the cessation from act, because sometimes a man who has been wont to commit several kinds of sin, renounces one and not the other; which is indeed due to God's assistance, but does not reach to the pardon of the sin.
2. In this saying of Ambrose "faith" cannot denote the faith whereby we believe in Christ, because, as Augustine says on Jn 15,22, "If I had not come, and spoken to them, they would not have sin" (viz. unbelief): "for this is the sin which contains all others": but it stands for consciousness, because sometimes a man receives pardon for a sin of which he is not conscious, through the punishment which he bears patiently.
3. Although sins are not connected in so far as they turn towards a mutable good, yet they are connected in so far as they turn away from the immutable Good, which applies to all mortal sins in common. and it is thus that they have the character of an offense which needs to be removed by Penance.
4. Debt as regards external things, e.g. money, is not opposed to friendship through which the debt is pardoned. hence one debt can be condoned without another. On the other hand, the debt of sin is opposed to friendship, and so one sin or offense is not pardoned without another; for it would seem absurd for anyone to ask even a man to forgive him one offense and not another.
5. The love whereby God loves man's nature, does not ordain man to the good of glory from which man is excluded by any mortal sin. but the love of grace, whereby mortal sin is forgiven, ordains man to eternal life, according to Rm 6,23: "The grace of God (is) life everlasting." Hence there is no comparison.

Summa Th. III EN Qu.85 a.2