Objection 1: It seems that the damned never repent of the evil they have done. For Bernard says concerning the Song of Songs [cf. De Consideratione v, 12; De Gratia et Libero Arbitrio ix], that “the damned always consent to the evil they have done!” Therefore, they never repent of the sins they have committed.
Objection 2: Further, the desire not to have sinned is a good will. But the damned will never have a good will. Therefore, the damned will never wish they had not sinned: and so the same conclusion follows as above.
Objection 3: Further, according to Damascene (De Fide Orth. ii), “death for man is what the fall was for the angels.” But the will of the angel after his fall is irrevocable, so that he cannot withdraw from the choice by which he previously sinned [cf. FP, Question [64], Article [21]]. Therefore, the damned also cannot repent of the sins they have committed.
Objection 4: Further, the wickedness of the damned in hell will be greater than that of sinners in the world. Now, in this world, some sinners do not repent of the sins they have committed, either through blindness of mind, like heretics, or through hardness, like those “who rejoice when they have done evil, and exult in the worst things” (Prov 2:14). Therefore, etc.
On the contrary, it is said of the damned (Wis 5:3): “They repent within themselves [Vulg.: ‘They speak within themselves, repenting’].” Further, the Philosopher says (Ethic. ix, 4) that “the wicked are full of repentance; for afterwards they are pained by what they previously took pleasure in.” Therefore, the damned, since they are the worst, repent all the more.
I answer that a person can repent of a sin in two ways: in one way directly, in another way indirectly. One repents of a sin directly who hates the sin as such; and one repents indirectly who hates it because of something connected with it, for example, punishment or something of that sort. Accordingly, the wicked will not repent of their sins directly, because the consent to the wickedness of the sin will remain in them; but they will repent indirectly, insofar as they will suffer the punishment imposed on them for the sin.
Reply to Objection 1: The damned will desire the wickedness, but shrink from the punishment: and so they indirectly repent of the wickedness committed.
Reply to Objection 2: To wish not to have sinned because of the baseness of vice is a good will; but this will shall not be in the wicked.
Reply to Objection 3: It will be possible for the damned to repent of their sins without turning their will away from the sin, because they will not shrink from what they previously desired in their sins, but from something else, namely, the punishment.
Reply to Objection 4: However hardened people may be in this world, they repent of their sins indirectly when they are punished for them. Thus Augustine says (Quaest. 83, qu. 36): “We see that the wildest beasts are kept from their greatest pleasures by fear of pain.”
Source: Summa Theologiae Supplement, Question 98, Article 2