[III.q.88.a.2.arg.1] It would seem that sins do not return through ingratitude, which is shown especially in four kinds of sin, viz., hatred of one's neighbor, apostasy from faith, contempt of confession and regret for past repentance, and which have been expressed in the following verse: "Fratres odit, apostata fit, spernitque, fateri, Poenituisse piget, pristina culpa redit." For the more grievous the sin committed against God after one has received the grace of pardon, the greater the ingratitude. But there are sins more grievous than these, such as blasphemy against God, and the sin against the Holy Ghost. Therefore it seems that sins already pardoned do not return through ingratitude as manifested in these sins, any more than as shown in other sins.

[III.q.88.a.2.arg.2] Further, Rabanus says: "God delivered the wicked servant to the torturers, until he should pay the whole debt, because a man will be deemed punishable not only for the sins he commits after Baptism, but also for original sin which was taken away when he was baptized." Now venial sins are reckoned among our debts, since we pray in their regard: "Forgive us our trespasses [debita]." Therefore they too return through ingratitude; and, in like manner seemingly, sins already pardoned return through venial sins, and not only through those sins mentioned above.

[III.q.88.a.2.arg.3] Further, ingratitude is all the greater, according as one sins after receiving a greater favor. Now innocence whereby one avoids sin is a Divine favor, for Augustine says (Confess. ii): "Whatever sins I have avoided committing, I owe it to Thy grace." Now innocence is a greater gift, than even the forgiveness of all sins. Therefore the first sin committed after innocence is no less an ingratitude to God, than a sin committed after repentance, so that seemingly ingratitude in respect of the aforesaid sins is not the chief cause of sins returning.

[III.q.88.a.2.sc] Gregory says (Moral. xviii [Cf. Dial. iv): "It is evident from the words of the Gospel that if we do not forgive from our hearts the offenses committed against us, we become once more accountable for what we rejoiced in as forgiven through Penance": so that ingratitude implied in the hatred of one's brother is a special cause of the return of sins already forgiven: and the same seems to apply to the others.

[III.q.88.a.2.co] As stated above (Article 1), sins pardoned through Penance are said to return, in so far as their debt of punishment, by reason of ingratitude, is virtually contained in the subsequent sin. Now one may be guilty of ingratitude in two ways: first by doing something against the favor received, and, in this way, man is ungrateful to God in every mortal sin whereby he offends God Who forgave his sins, so that by every subsequent mortal sin, the sins previously pardoned return, on account of the ingratitude. Secondly, one is guilty of ingratitude, by doing something not only against the favor itself, but also against the form of the favor received. If this form be considered on the part of the benefactor, it is the remission of something due to him; wherefore he who does not forgive his brother when he asks pardon, and persists in his hatred, acts against this form. If, however, this form be taken in regard to the penitent who receives this favor, we find on his part a twofold movement of the free-will. The first is the movement of the free-will towards God, and is an act of faith quickened by charity; and against this a man acts by apostatizing from the faith. The second is a movement of the free-will against sin, and is the act of penance. This act consists first, as we have stated above (85, 2,5) in man's detestation of his past sins; and against this a man acts when he regrets having done penance. Secondly, the act of penance consists in the penitent purposing to subject himself to the keys of the Church by confession, according to Psalm 31:5: "I said: I will confess against myself my injustice to the Lord: and Thou hast forgiven the wickedness of my sin": and against this a man acts when he scorns to confess as he had purposed to do.

Accordingly it is said that the ingratitude of sinners is a special cause of the return of sins previously forgiven.

[III.q.88.a.2.ad.1] This is not said of these sins as though they were more grievous than others, but because they are more directly opposed to the favor of the forgiveness of sin.

[III.q.88.a.2.ad.2] Even venial sins and original sin return in the way explained above, just as mortal sins do, in so far as the favor conferred by God in forgiving those sins is despised. A man does not, however, incur ingratitude by committing a venial sin, because by sinning venially man does not act against God, but apart from Him, wherefore venial sins nowise cause the return of sins already forgiven.

[III.q.88.a.2.ad.3] A favor can be weighed in two ways. First by the quantity of the favor itself, and in this way innocence is a greater favor from God than penance, which is called the second plank after shipwreck (cf. 84, 6). Secondly, a favor may be weighed with regard to the recipient, who is less worthy, wherefore a greater favor is bestowed on him, so that he is the more ungrateful if he scorns it. In this way the favor of the pardon of sins is greater when bestowed on one who is altogether unworthy, so that the ingratitude which follows is all the greater.

[III.q.88.a.3.arg.1] It would seem that the debt of punishment arising through ingratitude in respect of a subsequent sin is as great as that of the sins previously pardoned. Because the greatness of the favor of the pardon of sins is according to the greatness of the sin pardoned, and so too, in consequence, is the greatness of the ingratitude whereby this favor is scorned. But the greatness of the consequent debt of punishment is in accord with the greatness of the ingratitude. Therefore the debt of punishment arising through ingratitude in respect of a subsequent sin is as great as the debt of punishment due for all the previous sins.

[III.q.88.a.3.arg.2] Further, it is a greater sin to offend God than to offend man. But a slave who is freed by his master returns to the same state of slavery from which he was freed, or even to a worse state. Much more therefore he that sins against God after being freed from sin, returns to the debt of as great a punishment as he had incurred before.

[III.q.88.a.3.arg.3] Further, it is written (Matthew 18:34) that "his lord being angry, delivered him" (whose sins returned to him on account of his ingratitude) "to the torturers, until he paid all the debt." But this would not be so unless the debt of punishment incurred through ingratitude were as great as that incurred through all previous sins. Therefore an equal debt of punishment returns through ingratitude.

[III.q.88.a.3.sc] It is written (Deuteronomy 25:2): "According to the measure of the sin shall the measure also of the stripes be," whence it is evident that a great debt of punishment does not arise from a slight sin. But sometimes a subsequent mortal sin is much less grievous than any one of those previously pardoned. Therefore the debt of punishment incurred through subsequent sins is not equal to that of sins previously forgiven.

[III.q.88.a.3.co] Some have maintained that the debt of punishment incurred through ingratitude in respect of a subsequent sin is equal to that of the sins previously pardoned, in addition to the debt proper to this subsequent sin. But there is no need for this, because, as stated above (Article 1), the debt of punishment incurred by previous sins does not return on account of a subsequent sin, as resulting from the acts of the subsequent sin. Wherefore the amount of the debt that returns must be according to the gravity of the subsequent sin.

It is possible, however, for the gravity of the subsequent sin to equal the gravity of all previous sins. But it need not always be so, whether we speak of the gravity which a sin has from its species (since the subsequent sin may be one of simple fornication, while the previous sins were adulteries, murders, or sacrileges); or of the gravity which it incurs through the ingratitude connected with it. For it is not necessary that the measure of ingratitude should be exactly equal to the measure of the favor received, which latter is measured according to the greatness of the sins previously pardoned. Because it may happen that in respect of the same favor, one man is very ungrateful, either on account of the intensity of his scorn for the favor received, or on account of the gravity of the offense committed against the benefactor, while another man is slightly ungrateful, either because his scorn is less intense, or because his offense against the benefactor is less grave. But the measure of ingratitude is proportionately equal to the measure of the favor received: for supposing an equal contempt of the favor, or an equal offense against the benefactor, the ingratitude will be so much the greater, as the favor received is greater.

Hence it is evident that the debt of punishment incurred by a subsequent sin need not always be equal to that of previous sins; but it must be in proportion thereto, so that the more numerous or the greater the sins previously pardoned, the greater must be the debt of punishment incurred by any subsequent mortal sin whatever.

[III.q.88.a.3.ad.1] The favor of the pardon of sins takes its absolute quantity from the quantity of the sins previously pardoned: but the sin of ingratitude does not take its absolute quantity from the measure of the favor bestowed, but from the measure of the contempt or of the offense, as stated above: and so the objection does not prove.

[III.q.88.a.3.ad.2] A slave who has been given his freedom is not brought back to his previous state of slavery for any kind of ingratitude, but only when this is grave.

[III.q.88.a.3.ad.3] He whose forgiven sins return to him on account of subsequent ingratitude, incurs the debt for all, in so far as the measure of his previous sins is contained proportionally in his subsequent ingratitude, but not absolutely, as stated above.