Chapter — Prümmer, Manuale Theologiae Moralis
Chapter I. On Injustice In General
Notions. Just as the words right and justice are employed in various senses, so also injury and injustice. For first, injustice generally signifies the state of sin or even sin itself; then, everything which is opposed to the cardinal virtue of justice, whether general or particular. Hence transgressors of the law, judges who are acceptors of persons, thieves, robbers are called unjust. Here we do not treat of injustice in the first sense, but only of injustice insofar as it is directly opposed to the cardinal virtue of justice (whether general or particular). - Injustice and injury are sometimes, especially by modern authors, for example Waffelaert,1 Tanquerey,2 distinguished in such a way that injustice signifies the habit, but injury the act. The matter is of small moment.
1 Tract. de iust. II, n. 2.
2 Synopsis Theol. mor. de virt. iust. n. 264.
74. Principle 1. a) Injustice or injury, which is opposed to the cardinal virtue of justice, is a mortal sin from its genus; b) but it can be a light sin either from imperfection of act (i.e. from inadvertence or imperfect consent), or from smallness of matter.
a) Thus all teach. Sacred Scripture itself testifies that at least some acts of injustice are mortal sin; for example: "Do not err: ... Neither thieves ... nor the rapacious shall possess the kingdom of God."3 Moreover if some acts of a vice, without any other moral species added, are mortal sins, it follows that such a vice from its genus is a mortal sin. - The same is clear from reason; for justice is exceedingly necessary for social life, so that it can deservedly be called the foundation of the good and peace of the community, and without it the peaceful cohabitation of men is wholly impossible. Therefore he who gravely violates justice commits great damage and consequently grave sin. Besides, charity can be gravely violated through acts of injustice, which are accustomed to cause sadness, quarrels, hatreds, damages, etc., to one's neighbor. But a violation of charity from its genus is a mortal sin.
b) Therefore injustice from its genus is a mortal sin. But it is most difficult to determine in particular when its individual acts are mortal or venial sins from gravity or lightness of matter. On the contrary, it is not so difficult to determine when there is imperfection of act from inadvertence or from imperfect consent.
As a general rule concerning gravity of matter it can be held: injustice is a grave sin if from it notable damage has arisen either to one's neighbor or to the common good, or, as St. Thomas says:4 "Sins which are committed against one's neighbor are to be weighed, in themselves indeed, according to the harms which are inflicted on one's neighbor, because from this they have the ratio of fault." This rule is explained: every injustice causes damage, and indeed ordinarily a twofold damage, namely to one's neighbor and to the common good; for example, a thief taking away a sum of 100 francs causes damage: 1. to the legitimate proprietor, as is clear of itself; 2. to the common good, because he disturbs common peace, public tranquillity, and the mutual conjunction of men. - The same rule can also be expressed in this way: injustice is a grave sin as often as both he who suffers the damage and the governor of the community are reasonably gravely unwilling. Whence, for example, if someone takes 2 francs from a poor workman, that workman himself and the governor are reasonably and seriously unwilling; but if someone takes 100 francs from a very rich man, perhaps great injurious damage is not caused to that man, nevertheless the superior of the community must be gravely unwilling that such thefts be committed in his territory. - If the proprietor is gravely unwilling not on account of the objective value of the thing injured, but on account of a subjective and excessively exaggerated affection for the thing, for example for a beloved little bird, then the voluntary injury of such a thing can indeed be a grave sin against charity, but not against justice.
3 1 Cor. 6, 10.
4 S. theol. 2, 2, q. 73, a. 3.
75. Principle 2. All injuries indeed are opposed to the virtue of justice, but nevertheless they are not of the same lowest moral species, and they are distinguished according to formally diverse objects.
Hence the injustice committed in theft is one thing, that in homicide another, that in detraction another, etc. But the reason is that diverse vices can be opposed to one and the same virtue. Especially two great categories of injustice are customarily distinguished, namely the unjust taking away of another's thing and the unjust damaging of one's neighbor in his diverse goods. Whence we shall treat each category individually below.
76. Principle 3. The unjust, speaking per se and formally, a) no one can do except one willing, b) nor suffer except one unwilling.
Thus St. Thomas writes most truly and in pregnant style.5 The first part of this saying is clear of itself, because no one can sin except willingly. But formal injustice is always sin. For formal injustice, which someone knowingly and willingly commits, must be distinguished from material injustice, which indeed objectively violates the right of another, but without fault of the agent. Formal injustice, which is opposed to commutative justice and efficiently and really causes damage to one's neighbor, induces an obligation of restitution, but material injustice does not - at least not always - as will be said below.
The other part of the above-mentioned sentence is also expressed in Rule of Law 27 in VI: "To one knowing and consenting, neither injury nor deceit is done"; nevertheless it needs some explanation, because it is not true unless consent has the following conditions: a) that it be free. Whence, for example, if someone compelled by a robber consents that money be taken away from him, he nevertheless suffers injury and can reclaim the money taken away; b) that it be lawful. For in many cases a man cannot lawfully consent, because namely he does not have perfect dominion, or because there is question of inalienable rights; for example, he who kills one consenting sins and commits injustice; likewise he who commits adultery with a wife while the husband consents;6 likewise he who strikes a cleric renouncing the privilege of the canon, etc. But when someone has perfect dominion of some thing, then no injury is done to him when he wills it; for example, no injury is done to a rich man having apples in his garden, and not unwilling that neighboring boys usurp those apples, if the boys really take away the apples.
Since, therefore, formal injustice does not proceed except from one knowing and willing it, the question arises how this knowledge and will influence the external act, especially with respect to the obligation of restitution; or more briefly: whether the intention of harming always renders the external act unjust. To this question I answer thus: if someone has the intention of harming another, he indeed sins, for he commits mental injustice, but he is not bound to restitution unless the external act placed from this evil intention is also by itself alone against justice. For example, if a private man, from hatred toward an enemy, does not save his house burning, although he can easily do this, he indeed commits grave sin, but he is not bound to restitution, because the external act of saving the house is prescribed to him not from justice, but from charity alone. The judge who, according to the laws indeed, but chiefly from an intention of harming, condemns the guilty person, sins! But he is not bound to restitution, because his external action is not unjust. But the reason for this response is taken from the character of commutative justice, in which above all the "mean of the thing" must be observed. But there is never an obligation of restitution unless the mean of the thing has in reality been injured.
5 S. theol. 2, 2, q. 59, a. 3.
6 Cf. proposition 50 condemned by Innocent XI: "Copulation with a married woman, with the husband consenting, is not adultery; and therefore it suffices in confession to say that one has fornicated" (Denz. n. 1200).