Although restitution pertains to the common responsibilities of Christian life rather than to Christian moral principles, I discuss the topic briefly to distinguish restitution from penance.
Restitution for harm done is an obligation which follows in strict justice from all personal wrongdoing which unjustly causes harm to anyone. Harm is actual, definite damage of any sort. It is distinct from the inherent moral evil of sin, which is made up for by penance. The moral evil to oneself, to one’s relationship with other persons, and to God is built into sin; the need to satisfy for this moral evil by penance follows whether one has unjustly harmed anyone or not.
An example will clarify this distinction. Suppose I steal someone’s car. Morally, I need to repent and do penance. But also, as a matter of justice, I have done the harm of taking another’s property, and I must give the car back. Perhaps I am caught and the police restore the car to its rightful owner. Still, I must repent and do penance to get straightened out morally. Perhaps, however, the person from whom I stole the car is a billionaire; when, though not having been apprehended, I nevertheless repent and offer him the car, he tells me to keep it, since he never liked it anyway and hoped I would steal it. In this case, I do not have to make restitution or reparation of harm, since there is no injustice in keeping the car. But I still have to do penance, for my sin has upset the moral harmony within myself, with other people, and with God.
Restitution for harm is most often recognized as a moral obligation in matters of money and property. However, the obligation is wider. If a person harms others through bad example, he or she ought to try to help those scandalized to know that the example was bad and ought not to be followed. If a person harms another by careless, unfair talk, then there is an obligation to try to correct the erroneous impressions which have been given. Thus, whenever one repents of any sin, one needs to ask oneself who has been harmed, whether the harm was caused unjustly (willing accomplices in one’s sins are not harmed unjustly, and so restitution is not due them), and whether and how restitution might be made.
One who does not conscientiously consider the obligation to make restitution is only half-sincere in repenting. Of course, restitution, although distinct in concept from penance, can also serve as penance, even as part of a sacramentally imposed penance.
The distinction between restitution and penance is important, however, and must be borne in mind when one acts with only venial guilt but causes serious harm to others. For example, the thoughtless word which does harm to another demands careful effort to remedy the harm, even if the thoughtlessness made the deed virtually blameless. In such a case, one need not repent as if of mortal sin, for one has not committed mortal sin. Still, the obligation to make restitution is real.