I answer that, To restore is seemingly the same as to reinstate a person in the possession or dominion of his thing, so that in restitution we consider the equality of justice attending the payment of one thing for another, and this belongs to commutative justice. Hence restitution is an act of commutative justice, occasioned by one person having what belongs to another, either with his consent, for instance on loan or deposit, or against his will, as in robbery or theft.
Reply Obj. 1: That which is not due to another is not his properly speaking, although it may have been his at some time: wherefore it is a mere gift rather than a restitution, when anyone renders to another what is not due to him. It is however somewhat like a restitution, since the thing itself is materially the same; yet it is not the same in respect of the formal aspect of justice, which considers that thing as belonging to this particular man: and so it is not restitution properly so called.
Reply Obj. 2: In so far as the word restitution denotes something done over again, it implies identity of object. Hence it would seem originally to have applied chiefly to external things, which can pass from one person to another, since they remain the same both substantially and in respect of the right of dominion. But, even as the term "commutation" has passed from such like things to those actions and passions which confer reverence or injury, harm or profit on another person, so too the term "restitution" is applied, to things which though they be transitory in reality, yet remain in their effect; whether this touch his body, as when the body is hurt by being struck, or his reputation, as when a man remains defamed or dishonored by injurious words.
Reply Obj. 3: Compensation is made by the distributor to the man to whom less was given than his due, by comparison of thing with thing, when the latter receives so much the more according as he received less than his due: and consequently it pertains to commutative justice. _______________________
SECOND ARTICLE [II-II, Q. 62, Art. 2]
Whether Restitution of What Has Been Taken Away Is Necessary for
Salvation?
Objection 1: It would seem that it is not necessary to restore what has been taken away. For that which is impossible is not necessary for salvation. But sometimes it is impossible to restore what has been taken, as when a man has taken limb or life. Therefore it does not seem necessary for salvation to restore what one has taken from another.
Obj. 2: Further, the commission of a sin is not necessary for salvation, for then a man would be in a dilemma. But sometimes it is impossible, without sin, to restore what has been taken, as when one has taken away another's good name by telling the truth. Therefore it is not necessary for salvation to restore what one has taken from another.
Obj. 3: Further, what is done cannot be undone. Now sometimes a man loses his personal honor by being unjustly insulted. Therefore that which has been taken from him cannot be restored to him: so that it is not necessary for salvation to restore what one has taken.
Obj. 4: Further, to prevent a person from obtaining a good thing is seemingly the same as to take it away from him, since "to lack little is almost the same as to lack nothing at all," as the Philosopher says (Phys. ii, 5). Now when anyone prevents a man from obtaining a benefice or the like, seemingly he is not bound to restore the benefice, since this would be sometimes impossible. Therefore it is not necessary for salvation to restore what one has taken.