Article — Wouters, Manual of Moral Theology
Article I. Notion, Obligation, and Titles of Restitution
I. Notion of restitution. Restitution is the reparation of another's violated strict right, or it is an act of commutative justice by which someone returns another's thing or compensates damage unjustly inflicted by himself.
Restitution differs: 1° from satisfaction, which consists in the reparation of an offense inflicted on someone; 2° from payment, which neither returns another's thing nor supposes damage unjustly inflicted.
II. Obligation of restitution. 1. The obligation is clear both from Sacred Scripture1 and from the reason brought forward in n. 978.
The obligation of restitution is grave by its kind, that is, grave or light according as the matter to be restored is grave or light; for the said obligation corresponds to the obligation of not committing injustice; and that obligation is grave by its kind (n. 978). Nevertheless, the gravity of the obligation ceases if so much has been restored that the remaining matter ceases to be grave (St. Alphonsus, III, 553).
In doubt whether the thing or quantity taken away by you, destroyed, or consumed, is grave, you are bound under grave obligation to restore, because, once another's certain right to a thing or to a quantity has been posited, it is gravely illicit for you to expose yourself to the danger of continuing grave damage. But in doubt whether you took, destroyed, or consumed more or less, for example whether you stole 20 or 10 florins, you are bound only to restoring the lesser amount, because the fact founding the obligation of restoring more is doubtful (n. 228; St. Alphonsus, III, 706).
It is disputed whether one who has harmed someone in a kind of goods in which he cannot restore must compensate the injury with money, for instance if someone has mutilated or defamed another.
Response. St. Thomas (II-II, q. 62, a. 2, ad 1 and 2) seems to affirm, because where an equivalent cannot be restored, there must be made the compensation which is possible. Thus also Cajetan.2 St. Alphonsus, however, with others, deservedly holds the contrary as sufficiently probable. For "commutative justice obliges one to restore according to the equality of the damage inflicted. But where restitution is to be made in a different kind, there is no equality present, nor will there ever be any compensation of the damage; for by any money whatever the damage will by no means be repaired, either in whole or in part. And thus response is made to the opposite opinion" (St. Alphonsus, III, 627). There is added that a strict right must regard something determinate. But it cannot be determined what in a diverse order would have to be restored.
Corollary. In this case the injured person generally cannot provide for himself by occult compensation, because the debt is only probable; cf. however n. 1074. But where the injured person has received compensation in another kind from the one harming him, he can retain it, nor can the one who harmed now recover it by occult compensation (n. 1033).
1 Cf. Exod. 22:5; Tob. 2:21; Ezek. 33:15; Rom. 13:7; Jas. 5:4.
2 Summa, word Restitutio, cap. 2.
III. Titles of restitution, that is, the reasons or roots from which the obligation of restitution arises, are: 1° another's thing materially unjustly possessed; 2° another's thing formally unjustly accepted; 3° mere damaging, which takes place when someone merely injures the good of another, or unjustly impedes him from acquiring a good. A contract, whether not observed or violated, is referred according to the circumstances to one of the assigned titles (St. Alphonsus, III, 548).