Punishments, whether punishment with which parents punish their children for misbehaving, judges declare punishment for a crime, or God punishes men's sins, have various ends or purposes. Thomas Aquinas summarizes these purposes under two headings: 1. To restrain or inhibit voluntary evil; 2. to establish order there, where a crime has made disorder.
The evil of punishment is imposed to coerce and to order the evil of guilt. (De Malo, q. 1, a. 5, ad 7)
After the remission of sin, punishment is needed for two ends: to settle the debt, and to provide a remedy (In IV Sent., dist. 20, q. 1, a. 2, qa. 1)
Punishment as salutary: healing evils or preventing them
Inasmuch as punishment is aimed at restraining or hindering evil, Aquinas describes punishment as medicinal or salutary, either for the wrongdoer himself, or at least for the larger community. In the best case, the punishment helps to rehabilitate the wrongdoer, training him to live justly as a member of the larger human community; in any case, it helps secure the community freedom from injustice by deterring subsequent crimes by the one guilty of wrongdoing or by others, whom the threat of punishment deters from such crimes; making the criminal incapable of committing further crimes by imprisonment, exile, removal of status or authority used to commit crimes, etc.
Punishment as retribution: balancing out the wrong done
Inasmuch as punishment is aimed at balancing the crime, by which an individual has exerted their will against the requirements of justice and the common good, with an imposition by the community of something contrary to his will, Aquinas describes punishment as vindictive, or retributive.
We have an intuitive feeling: one who has done wrong has harmed another person or the community, thereby deprived that person and the community of some good, and so owes them a debt; again, one way of (at least partially) resolving this debt is by "paying back" the evil to the wrongdoer.
Where is the justice in this "payback"? What distinguishes this "payback" from mere vengeance, or the notion that "two wrongs (i.e., a wrong done to the wrongdoer) make a right"?
St. Thomas Aquinas writes:
"the failing of a voluntary action is the essence (constituit rationem) of sin and guilt, so the failing of any good imposed on someone contrary to the will of the one on whom it is imposed, is the essence of punishment. For punishment is imposed as a medicine for guilt, and as setting it in order. As medicine, inasmuch as man, by reason of punishment, is held back from guilt when, in order that he not suffer what is contrary to his will, he foregoes doing a disordered action that would otherwise please his will. It sets it in order, since by guilt man transgresses the limits of the natural order, giving more to his will than he ought. Hence he is led back to the order of justice by punishment, through which something is taken away from his will. From this it is evident that a fitting punishment is not given for guilt, unless the punishment is more contrary to the will than the guilt is pleasing. (Compendium theologiae, ch. 121)
A person who acts unjustly creates an inequality within the community, a disturbance of the order by which all are members of the community are fundamentally equally ordered to the common good of the community as participants in it. The inequality consists in an excessive exertion of the wrongdoer's will against the order of natural or civil law by which the common good is preserved and promoted. Insofar as freedom is a good, this exercise of free freed from the demands of law, is a kind of advantage the wrongdoer has arrogated to himself in comparison with other citizens: he enjoys freedom and other common goods of the community preserved by the order of law, while not respecting the equal right of others under that law.
This inequality, consisting in the exertion of an individual's will against the demands of law and the common good, may be removed, and equality of all citizens with respect to the common good and the law, by the imposition, by a competent authority, on the wrongdoer of something contrary to his will.
Since the purpose of punishment is the re-establishment of equality before the law, punishment can only be imposed by one authorized to apply the law in the name of the community; such an authority may also declare, in a particular case, that punishment will not be imposed (amnesty), which insofar as it is a judgment made by a lawful authority for the common good, is in its own way equally a re-establishment of the order of justice.
Retribution is essential in constituting punishment
In order for punishment to be just, indeed, to be punishment in the strict sense, it must have an element of retribution. Civil authorities might come upon of the idea of deterring theft by taking some random person, whipping them publicly, and announcing, "this and ten times more will be done to anyone who commits theft". This, however, would not be punishment, but terrorizing, not a just subordination of individual good to the common good, but the instrumentalization of individuals for the state.
Healing or inhibition of evil is the primary purpose of punishment in civil or human communities
Yet while retribution is necessary in order that punishment actually be punishment rather than merely a way of striking fear into the populace, it is not the principal goal. Aquinas sees the goal or purpose of punishments within civil communities (in contrast with punishment in purgatory or hell imposed by God as creator and ruler of the universe) as being medicine for or restraint of sin.
- Punishments are not directly intended by the legislator, but are medicines, as it were, for sin. And therefore the equitable person does not apply more pain than suffices for restraining sin. (Commentary on the Nicomachean Ethics V, lectio 16)
- The infliction of punishments should not be sought for its own sake, but punishments are inflicted as medicines for restraining sins. And thus they have the character of justice just insofar as they restrain sins. (ST (Summa Theologiae) II-II, q. 43, a. 7)
- The punishments of this present life are more medicinal than retributive, for retribution is reserved for the divine judgment. (ST II-II, q. 66, a. 6)
- The punishments of the present life are not sought for their own sake, because this is not the time of final retribution; but they are sought insofar as they are medicinal, aiding either the correction of the sinning person, or the good of the republic, whose tranquility is procured by the punishment of people who sin. (ST II-II, q. 68, a. 1)
- Vengeance is made by inflicting something painful on the sinner. Therefore we must consider the mind of the avenger. If he intends principally the evil for the one on whom he takes vengeance, and rests in that evil, vengeance is completely unlawful, since to delight in the evil of another person pertains to hatred, which is contrary to the charity by which we should love all men. Nor is someone excused, because he wills evil on someone who inflicted evil on him, just as one is not excused because he hates someone who hates him… but if the avenger principally looks to some good that is attained through punishing the sinner, e.g. his correction, or at least restraining him [from further sin] and quieting others, and the preservation of justice and the honor of God, vengeance can be licit, so long as the other suitable circumstances are present. (ST II-II, q. 108, a. 1)
- Vengeance is licit and virtuous insofar as it tends to restrain evils. (ST II-II, q. 108, a. 3)
- All mortal sinners are worthy of eternal death as regards the future retribution, which is according to the truth of the divine judgment. But the punishments in the present life are rather medicine (than retributive). And therefore the death penalty is only inflicted for those sins that result in grave harm to others. (ST II-II, q. 108, a. 3, ad 2)
Consequently, to consider retribution alone, or to punish merely to "pay someone back" for a crime committed, is an insufficient reason to punish, and therefore to punish in this way would be unjust. Again, to impose a greater punishment than necessary in order to attain the goals of healing the evil, and/or preventing or restraining future evils, is inappropriate and therefore unjust.
The goals of punishment set certain limits to what punishment may be suitable and just for a given crime, but also provide guidelines: the suitable punishment will depend on the nature of the crime, how voluntary the crime was and how set the wrongdoer's will is on wrongdoing, how prone people in general are to such a crime, whether the deed tends to be attractive or abhorrent, etc. I will return to this point in a subsequent post.
(Update August 8, 2018: two more citations from St. Thomas Aquinas added)