Summa Th. II-II EN Qu.65 a.3
Objection: 1. It would seem unlawful to imprison a man. An act which deals with undue matter is evil in its genus, as stated above (I-II 18,2). Now man, having a free-will, is undue matter for imprisonment which is inconsistent with free-will. Therefore it is unlawful to imprison a man.
2. Further, human justice should be ruled by Divine justice. Now according to Si 15,14, "God left man in the hand of his own counsel." Therefore it seems that a man ought not to be coerced by chains or prisons.
3. Further, no man should be forcibly prevented except from doing an evil deed; and any man can lawfully prevent another from doing this. If, therefore, it were lawful to imprison a man, in order to restrain him from evil deeds, it would be lawful for anyone to put a man in prison; and this is clearly false. Therefore the same conclusion follows.
On the contrary We read in Lv 24 that a man was imprisoned for the sin of blasphemy.
I answer that In the goods three things may be considered in due order. First, the substantial integrity of the body, and this is injured by death or maiming. Secondly, pleasure or rest of the senses, and to this striking or anything causing a sense of pain is opposed. Thirdly, the movement or use of the members, and this is hindered by binding or imprisoning or any kind of detention.Therefore it is unlawful to imprison or in any way detain a man, unless it be done according to the order of justice, either in punishment, or as a measure of precaution against some evil.
Reply to Objection: 1. A man who abuses the power entrusted to him deserves to lose it, and therefore when a man by sinning abuses the free use of his members, he becomes a fitting matter for imprisonment.
2. According to the order of His wisdom God sometimes restrains a sinner from accomplishing a sin, according to Jb 5,12: "Who bringeth to nought the designs of the malignant, so that their hand cannot accomplish what they had begun, while sometimes He allows them to do what they will." In like manner, according to human justice, men are imprisoned, not for every sin but for certain ones.
3. It is lawful for anyone to restrain a man for a time from doing some unlawful deed there and then: as when a man prevents another from throwing himself over a precipice, or from striking another. But to him alone who has the right of disposing in general of the actions and of the life of another does it belong primarily to imprison or fetter, because by so doing he hinders him from doing not only evil but also good deeds.
Objection: 1. It would seem that the sin is not aggravated by the fact that the aforesaid injuries are perpetrated on those who are connected with others. Such like injuries take their sinful character from inflicting an injury on another against his will. Now the evil inflicted on a man's own person is more against his will than that which is inflicted on a person connected with him. Therefore an injury inflicted on a person connected with another is less grievous.
2. Further, Holy Writ reproves those especially who do injuries to orphans and widows: hence it is written (Si 35,17): "He will not despise the prayers of the fatherless, nor the widow when she poureth out her complaint." Now the widow and the orphan are not connected with other persons. Therefore the sin is not aggravated through an injury being inflicted on one who is connected with others.
3. Further, the person who is connected has a will of his own just as the principal person has, so that something may be voluntary for him and yet against the will of the principal person, as in the case of adultery which pleases the woman but not the husband. Now these injuries are sinful in so far as they consist in an involuntary commutation. Therefore such like injuries are of a less sinful nature.
On the contrary It is written (Dt 28,32) as though indicating an aggravating circumstance: "Thy sons and thy daughters shall be given to another people, thy eyes looking on [*Vulg.: 'May thy sons and thy daughters be given,' etc.]."
I answer that Other things being equal, an injury is a more grievous sin according as it affects more persons; and hence it is that it is a more grievous sin to strike or injure a person in authority than a private individual, because it conduces to the injury of the whole community, as stated above (I-II 73,9). Now when an injury is inflicted on one who is connected in any way with another, that injury affects two persons, so that, other things being equal, the sin is aggravated by this very fact. It may happen, however, that in view of certain circumstances, a sin committed against one who is not connected with any other person, is more grievous, on account of either the dignity of the person, or the greatness of the injury.
Reply to Objection: 1. An injury inflicted on a person connected with others is less harmful to the persons with whom he is connected, than if it were perpetrated immediately on them, and from this point of view it is a less grievous sin. But all that belongs to the injury of the person with whom he is connected, is added to the sin of which a man is guilty through injuring the other one in himself.
2. Injuries done to widows and orphans are more insisted upon both through being more opposed to mercy, and because the same injury done to such persons is more grievous to them since they have no one to turn to for relief.
3. The fact that the wife voluntarily consents to the adultery, lessens the sin and injury, so far as the woman is concerned, for it would be more grievous, if the adulterer oppressed her by violence. But this does not remove the injury as affecting her husband, since "the wife hath not power of her own body; but the husband" (1Co 7,4). The same applies to similar cases. of adultery, however, as it is opposed not only to justice but also to chastity, we shall speak in the treatise on Temperance (Question , Article ).
We must now consider the sins opposed to justice, whereby a man injures his neighbor in his belongings; namely theft and robbery.
Under this head there are nine points of inquiry:
(1) Whether it is natural to man to possess external things?
(2) Whether it is lawful for a man to possess something as his own?
(3) Whether theft is the secret taking of another's property?
(4) Whether robbery is a species of sin distinct from theft?
(5) Whether every theft is a sin?
(6) Whether theft is a mortal sin?
(7) Whether it is lawful to thieve in a case of necessity?
(8) Whether every robbery is a mortal sin?
(9) Whether robbery is a more grievous sin than theft?
Objection: 1. It would seem that it is not natural for man to possess external things. For no man should ascribe to himself that which is God's. Now the dominion over all creatures is proper to God, according to Ps 23,1, "The earth is the Lord's," etc. Therefore it is not natural for man to possess external things.
2. Further, Basil in expounding the words of the rich man (Lc 12,18), "I will gather all things that are grown to me, and my goods," says [*Hom. in Luc. xii, 18]: "Tell me: which are thine? where did you take them from and bring them into being?" Now whatever man possesses naturally, he can fittingly call his own. Therefore man does not naturally possess external things.
3. Further, according to Ambrose (De Trin. i [*De Fide, ad Gratianum, i, 1]) "dominion denotes power." But man has no power over external things, since he can work no change in their nature. Therefore the possession of external things is not natural to man.
On the contrary It is written (Ps 8,8): "Thou hast subjected all things under his feet."
I answer that External things can be considered in two ways. First, as regards their nature, and this is not subject to the power of man, but only to the power of God Whose mere will all things obey. Secondly, as regards their use, and in this way, man has a natural dominion over external things, because, by his reason and will, he is able to use them for his own profit, as they were made on his account: for the imperfect is always for the sake of the perfect, as stated above (Question , Article ). It is by this argument that the Philosopher proves (Polit. i, 3) that the possession of external things is natural to man. Moreover, this natural dominion of man over other creatures, which is competent to man in respect of his reason wherein God's image resides, is shown forth in man's creation (Gn 1,26) by the words: "Let us make man to our image and likeness: and let him have dominion over the fishes of the sea," etc.
Reply to Objection: 1. God has sovereign dominion over all things: and He, according to His providence, directed certain things to the sustenance of man's body. For this reason man has a natural dominion over things, as regards the power to make use of them.
2. The rich man is reproved for deeming external things to belong to him principally, as though he had not received them from another, namely from God.
3. This argument considers the dominion over external things as regards their nature. Such a dominion belongs to God alone, as stated above.
Objection: 1. It would seem unlawful for a man to possess a thing as his own. For whatever is contrary to the natural law is unlawful. Now according to the natural law all things are common property: and the possession of property is contrary to this community of goods. Therefore it is unlawful for any man to appropriate any external thing to himself.
2. Further, Basil in expounding the words of the rich man quoted above (Article , Objection ), says: "The rich who deem as their own property the common goods they have seized upon, are like to those who by going beforehand to the play prevent others from coming, and appropriate to themselves what is intended for common use." Now it would be unlawful to prevent others from obtaining possession of common goods. Therefore it is unlawful to appropriate to oneself what belongs to the community.
3. Further, Ambrose says [*Serm. lxiv, de temp.], and his words are quoted in the Decretals [*Dist. xlvii., Can. Sicut hi.]: "Let no man call his own that which is common property": and by "common" he means external things, as is clear from the context. Therefore it seems unlawful for a man to appropriate an external thing to himself.
On the contrary Augustine says (De Haeres., haer. 40): "The 'Apostolici' are those who with extreme arrogance have given themselves that name, because they do not admit into their communion persons who are married or possess anything of their own, such as both monks and clerics who in considerable number are to be found in the Catholic Church." Now the reason why these people are heretics was because severing themselves from the Church, they think that those who enjoy the use of the above things, which they themselves lack, have no hope of salvation. Therefore it is erroneous to maintain that it is unlawful for a man to possess property.
I answer that Two things are competent to man in respect of exterior things. One is the power to procure and dispense them, and in this regard it is lawful for man to possess property. Moreover this is necessary to human life for three reasons. First because every man is more careful to procure what is for himself alone than that which is common to many or to all: since each one would shirk the labor and leave to another that which concerns the community, as happens where there is a great number of servants. Secondly, because human affairs are conducted in more orderly fashion if each man is charged with taking care of some particular thing himself, whereas there would be confusion if everyone had to look after any one thing indeterminately. Thirdly, because a more peaceful state is ensured to man if each one is contented with his own. Hence it is to be observed that quarrels arise more frequently where there is no division of the things possessed.The second thing that is competent to man with regard to external things is their use. In this respect man ought to possess external things, not as his own, but as common, so that, to wit, he is ready to communicate them to others in their need. Hence the Apostle says (1Tm 6,17-18): "Charge the rich of this world . . . to give easily, to communicate to others," etc.
Reply to Objection: 1. Community of goods is ascribed to the natural law, not that the natural law dictates that all things should be possessed in common and that nothing should be possessed as one's own: but because the division of possessions is not according to the natural law, but rather arose from human agreement which belongs to positive law, as stated above (Question , Articles ,3). Hence the ownership of possessions is not contrary to the natural law, but an addition thereto devised by human reason.
2. A man would not act unlawfully if by going beforehand to the play he prepared the way for others: but he acts unlawfully if by so doing he hinders others from going. In like manner a rich man does not act unlawfully if he anticipates someone in taking possession of something which at first was common property, and gives others a share: but he sins if he excludes others indiscriminately from using it. Hence Basil says (Hom. in Luc. xii, 18): "Why are you rich while another is poor, unless it be that you may have the merit of a good stewardship, and he the reward of patience?"
3. When Ambrose says: "Let no man call his own that which is common," he is speaking of ownership as regards use, wherefore he adds: "He who spends too much is a robber."
Objection: 1. It would seem that it is not essential to theft to take another's thing secretly. For that which diminishes a sin, does not, apparently, belong to the essence of a sin. Now to sin secretly tends to diminish a sin, just as, on the contrary, it is written as indicating an aggravating circumstance of the sin of some (Is 3,9): "They have proclaimed abroad their sin as Sodom, and they have not hid it." Therefore it is not essential to theft that it should consist in taking another's thing secretly.
2. Further, Ambrose says [*Serm. lxiv, de temp., Article , Objection , Can. Sicut hi.]: and his words are embodied in the Decretals [*Dist. xlvii]: "It is no less a crime to take from him that has, than to refuse to succor the needy when you can and are well off." Therefore just as theft consists in taking another's thing, so does it consist in keeping it back.
3. Further, a man may take by stealth from another, even that which is his own, for instance a thing that he has deposited with another, or that has been taken away from him unjustly. Therefore it is not essential to theft that it should consist in taking another's thing secretly.
On the contrary Isidore says (Etym. x): "'Fur' [thief] is derived from 'furvus' and so from 'fuscus' [dark], because he takes advantage of the night."
I answer that Three things combine together to constitute theft. The first belongs to theft as being contrary to justice, which gives to each one that which is his, so that it belongs to theft to take possession of what is another's. The second thing belongs to theft as distinct from those sins which are committed against the person, such as murder and adultery, and in this respect it belongs to theft to be about a thing possessed: for if a man takes what is another's not as a possession but as a part (for instance, if he amputates a limb), or as a person connected with him (for instance, if he carry off his daughter or his wife), it is not strictly speaking a case of theft. The third difference is that which completes the nature of theft, and consists in a thing being taken secretly: and in this respect it belongs properly to theft that it consists in "taking another's thing secretly."
Reply to Objection: 1. Secrecy is sometimes a cause of sin, as when a man employs secrecy in order to commit a sin, for instance in fraud and guile. In this way it does not diminish sin, but constitutes a species of sin: and thus it is in theft. In another way secrecy is merely a circumstance of sin, and thus it diminishes sin, both because it is a sign of shame, and because it removes scandal.
2. To keep back what is due to another, inflicts the same kind of injury as taking a thing unjustly: wherefore an unjust detention is included in an unjust taking.
3. Nothing prevents that which belongs to one person simply, from belonging to another in some respect: thus a deposit belongs simply to the depositor, but with regard to its custody it is the depositary's, and the thing stolen is the thief's, not simply, but as regards its custody.
Objection: 1. It would seem that theft and robbery are not sins of different species. For theft and robbery differ as "secret" and "manifest": because theft is taking something secretly, while robbery is to take something violently and openly. Now in the other kinds of sins, the secret and the manifest do not differ specifically. Therefore theft and robbery are not different species of sin.
2. Further, moral actions take their species from the end, as stated above (I-II 1,3; Question , Article ). Now theft and robbery are directed to the same end, viz. the possession of another's property. Therefore they do not differ specifically.
3. Further, just as a thing is taken by force for the sake of possession, so is a woman taken by force for pleasure: wherefore Isidore says (Etym. x) that "he who commits a rape is called a corrupter, and the victim of the rape is said to be corrupted." Now it is a case of rape whether the woman be carried off publicly or secretly. Therefore the thing appropriated is said to be taken by force, whether it be done secretly or publicly. Therefore theft and robbery do not differ.
On the contrary The Philosopher (Ethic. v, 2) distinguishes theft from robbery, and states that theft is done in secret, but that robbery is done openly.
I answer that Theft and robbery are vices contrary to justice, in as much as one man does another an injustice. Now "no man suffers an injustice willingly," as stated in Ethic. v, 9. Wherefore theft and robbery derive their sinful nature, through the taking being involuntary on the part of the person from whom something is taken. Now the involuntary is twofold, namely, through violence and through ignorance, as stated in Ethic. iii, 1. Therefore the sinful aspect of robbery differs from that of theft: and consequently they differ specifically.
Reply to Objection: 1. In the other kinds of sin the sinful nature is not derived from something involuntary, as in the sins opposed to justice: and so where there is a different kind of involuntary, there is a different species of sin.
2. The remote end of robbery and theft is the same. But this is not enough for identity of species, because there is a difference of proximate ends, since the robber wishes to take a thing by his own power, but the thief, by cunning.
3. The robbery of a woman cannot be secret on the part of the woman who is taken: wherefore even if it be secret as regards the others from whom she is taken, the nature of robbery remains on the part of the woman to whom violence is done.
Objection: 1. It would seem that theft is not always a sin. For no sin is commanded by God, since it is written (Si 15,21): "He hath commanded no man to do wickedly." Yet we find that God commanded theft, for it is written (Ex 12,35-36): "And the children of Israel did as the Lord had commanded Moses [Vulg.: 'as Moses had commanded']. . . and they stripped the Egyptians." Therefore theft is not always a sin.
2. Further, if a man finds a thing that is not his and takes it, he seems to commit a theft, for he takes another's property. Yet this seems lawful according to natural equity, as the jurists hold. [*See loc. cit. in Reply.] Therefore it seems that theft is not always a sin.
3. Further, he that takes what is his own does not seem to sin, because he does not act against justice, since he does not destroy its equality. Yet a man commits a theft even if he secretly take his own property that is detained by or in the safe-keeping of another. Therefore it seems that theft is not always a sin.
On the contrary It is written (Ex 20,15): "Thou shalt not steal."
I answer that If anyone consider what is meant by theft, he will find that it is sinful on two counts. First, because of its opposition to justice, which gives to each one what is his, so that for this reason theft is contrary to justice, through being a taking of what belongs to another. Secondly, because of the guile or fraud committed by the thief, by laying hands on another's property secretly and cunningly. Wherefore it is evident that every theft is a sin.
Reply to Objection: 1. It is no theft for a man to take another's property either secretly or openly by order of a judge who has commanded him to do so, because it becomes his due by the very fact that it is adjudicated to him by the sentence of the court. Hence still less was it a theft for the Israelites to take away the spoils of the Egyptians at the command of the Lord, Who ordered this to be done on account of the ill-treatment accorded to them by the Egyptians without any cause: wherefore it is written significantly (Sg 10,19): "The just took the spoils of the wicked."
2. With regard to treasure-trove a distinction must be made. For some there are that were never in anyone's possession, for instance precious stones and jewels, found on the seashore, and such the finder is allowed to keep [*Dig. I, viii, De divis. rerum: Inst. II, i, De rerum divis.]. The same applies to treasure hidden underground long since and belonging to no man, except that according to civil law the finder is bound to give half to the owner of the land, if the treasure trove be in the land of another person [*Inst. II, i, 39: Cod. X, xv, De Thesauris]. Hence in the parable of the Gospel (Mt 13,44) it is said of the finder of the treasure hidden in a field that he bought the field, as though he purposed thus to acquire the right of possessing the whole treasure. On the other Land the treasure-trove may be nearly in someone's possession: and then if anyone take it with the intention, not of keeping it but of returning it to the owner who does not look upon such things as unappropriated, he is not guilty of theft. In like manner if the thing found appears to be unappropriated, and if the finder believes it to be so, although he keep it, he does not commit a theft [*Inst. II, i, 47]. In any other case the sin of theft is committed [*Dig. XLI, i, De acquirend, rerum dominio, 9: Inst. II, i, 48]: wherefore Augustine says in a homily (Serm. clxxviii; De Verb. Apost.): "If thou hast found a thing and not returned it, thou hast stolen it" (Dig. xiv, 5, can. Si quid invenisti).
3. He who by stealth takes his own property which is deposited with another man burdens the depositary, who is bound either to restitution, or to prove himself innocent. Hence he is clearly guilty of sin, and is bound to ease the depositary of his burden. On the other hand he who, by stealth, takes his own property, if this be unjustly detained by another, he sins indeed; yet not because he burdens the retainer, and so he is not bound to restitution or compensation: but he sins against general justice by disregarding the order of justice and usurping judgment concerning his own property. Hence he must make satisfaction to God and endeavor to allay whatever scandal he may have given his neighbor by acting this way.
Objection: 1. It would seem that theft is not a mortal sin. For it is written (Pr 6,30): "The fault is not so great when a man hath stolen." But every mortal sin is a great fault. Therefore theft is not a mortal sin.
2. Further, mortal sin deserves to be punished with death. But in the Law theft is punished not by death but by indemnity, according to Ex 22,1, "If any man steal an ox or a sheep . . . he shall restore have oxen for one ox, and four sheep for one sheep." Therefore theft is not a mortal sin.
3. Further, theft can be committed in small even as in great things. But it seems unreasonable for a man to be punished with eternal death for the theft of a small thing such as a needle or a quill. Therefore theft is not a mortal sin.
On the contrary No man is condemned by the Divine judgment save for a mortal sin. Yet a man is condemned for theft, according to Zach. 5:3, "This is the curse that goeth forth over the face of the earth; for every thief shall be judged as is there written." Therefore theft is a mortal sin.
I answer that As stated above (Question , Article ; I-II 72,5), a mortal sin is one that is contrary to charity as the spiritual life of the soul. Now charity consists principally in the love of God, and secondarily in the love of our neighbor, which is shown in our wishing and doing him well. But theft is a means of doing harm to our neighbor in his belongings; and if men were to rob one another habitually, human society would be undone. Therefore theft, as being opposed to charity, is a mortal sin.
Reply to Objection: 1. The statement that theft is not a great fault is in view of two cases. First, when a person is led to thieve through necessity. This necessity diminishes or entirely removes sin, as we shall show further on (Article ). Hence the text continues: "For he stealeth to fill his hungry soul." Secondly, theft is stated not to be a great fault in comparison with the guilt of adultery, which is punished with death. Hence the text goes on to say of the thief that "if he be taken, he shall restore sevenfold . . . but he that is an adulterer . . . shall destroy his own soul."
2. The punishments of this life are medicinal rather than retributive. For retribution is reserved to the Divine judgment which is pronounced against sinners "according to truth" (Rm 2,2). Wherefore, according to the judgment of the present life the death punishment is inflicted, not for every mortal sin, but only for such as inflict an irreparable harm, or again for such as contain some horrible deformity. Hence according to the present judgment the pain of death is not inflicted for theft which does not inflict an irreparable harm, except when it is aggravated by some grave circumstance, as in the case of sacrilege which is the theft of a sacred thing, of peculation, which is theft of common property, as Augustine states (Tract. 1, Super Joan.), and of kidnaping which is stealing a man, for which the pain of death is inflicted (Ex 21,16).
3. Reason accounts as nothing that which is little: so that a man does not consider himself injured in very little matters: and the person who takes such things can presume that this is not against the will of the owner. And if a person take such like very little things, he may be proportionately excused from mortal sin. Yet if his intention is to rob and injure his neighbor, there may be a mortal sin even in these very little things, even as there may be through consent in a mere thought.
Objection: 1. It would seem unlawful to steal through stress of need. For penance is not imposed except on one who has sinned. Now it is stated (Extra, De furtis, Cap. Si quis): "If anyone, through stress of hunger or nakedness, steal food, clothing or beast, he shall do penance for three weeks." Therefore it is not lawful to steal through stress of need.
2. Further, the Philosopher says (Ethic. ii, 6) that "there are some actions whose very name implies wickedness," and among these he reckons theft. Now that which is wicked in itself may not be done for a good end. Therefore a man cannot lawfully steal in order to remedy a need.
3. Further, a man should love his neighbor as himself. Now, according to Augustine (Contra Mendac. vii), it is unlawful to steal in order to succor one's neighbor by giving him an alms. Therefore neither is it lawful to steal in order to remedy one's own needs.
On the contrary In cases of need all things are common property, so that there would seem to be no sin in taking another's property, for need has made it common.
I answer that Things which are of human right cannot derogate from natural right or Divine right. Now according to the natural order established by Divine Providence, inferior things are ordained for the purpose of succoring man's needs by their means. Wherefore the division and appropriation of things which are based on human law, do not preclude the fact that man's needs have to be remedied by means of these very things. Hence whatever certain people have in superabundance is due, by natural law, to the purpose of succoring the poor. For this reason Ambrose [*Loc. cit., Article , Objection ] says, and his words are embodied in the Decretals (Dist. xlvii, can. Sicut ii): "It is the hungry man's bread that you withhold, the naked man's cloak that you store away, the money that you bury in the earth is the price of the poor man's ransom and freedom."Since, however, there are many who are in need, while it is impossible for all to be succored by means of the same thing, each one is entrusted with the stewardship of his own things, so that out of them he may come to the aid of those who are in need. Nevertheless, if the need be so manifest and urgent, that it is evident that the present need must be remedied by whatever means be at hand (for instance when a person is in some imminent danger, and there is no other possible remedy), then it is lawful for a man to succor his own need by means of another's property, by taking it either openly or secretly: nor is this properly speaking theft or robbery.
Reply to Objection: 1. This decretal considers cases where there is no urgent need.
2. It is not theft, properly speaking, to take secretly and use another's property in a case of extreme need: because that which he takes for the support of his life becomes his own property by reason of that need.
3. In a case of a like need a man may also take secretly another's property in order to succor his neighbor in need.
Objection: 1. It would seem that robbery may be committed without sin. For spoils are taken by violence, and this seems to belong to the essence of robbery, according to what has been said (Article ). Now it is lawful to take spoils from the enemy; for Ambrose says (De Patriarch. 4 [*De Abraham i, 3]): "When the conqueror has taken possession of the spoils, military discipline demands that all should be reserved for the sovereign," in order, to wit, that he may distribute them. Therefore in certain cases robbery is lawful.
2. Further, it is lawful to take from a man what is not his. Now the things which unbelievers have are not theirs, for Augustine says (Ep ad Vincent. Donat. xciii.): "You falsely call things your own, for you do not possess them justly, and according to the laws of earthly kings you are commanded to forfeit them." Therefore it seems that one may lawfully rob unbelievers.
3. Further, earthly princes violently extort many things from their subjects: and this seems to savor of robbery. Now it would seem a grievous matter to say that they sin in acting thus, for in that case nearly every prince would be damned. Therefore in some cases robbery is lawful.
On the contrary Whatever is taken lawfully may be offered to God in sacrifice and oblation. Now this cannot be done with the proceeds of robbery, according to Is 61,8, "I am the Lord that love judgment, and hate robbery in a holocaust." Therefore it is not lawful to take anything by robbery.
I answer that Robbery implies a certain violence and coercion employed in taking unjustly from a man that which is his. Now in human society no man can exercise coercion except through public authority: and, consequently, if a private individual not having public authority takes another's property by violence, he acts unlawfully and commits a robbery, as burglars do. As regards princes, the public power is entrusted to them that they may be the guardians of justice: hence it is unlawful for them to use violence or coercion, save within the bounds of justice---either by fighting against the enemy, or against the citizens, by punishing evil-doers: and whatever is taken by violence of this kind is not the spoils of robbery, since it is not contrary to justice. On the other hand to take other people's property violently and against justice, in the exercise of public authority, is to act unlawfully and to be guilty of robbery; and whoever does so is bound to restitution.
Reply to Objection: 1. A distinction must be made in the matter of spoils. For if they who take spoils from the enemy, are waging a just war, such things as they seize in the war become their own property. This is no robbery, so that they are not bound to restitution. Nevertheless even they who are engaged in a just war may sin in taking spoils through cupidity arising from an evil intention, if, to wit, they fight chiefly not for justice but for spoil. For Augustine says (De Verb. Dom. xix; Serm. lxxxii) that "it is a sin to fight for booty." If, however, those who take the spoil, are waging an unjust war, they are guilty of robbery, and are bound to restitution.
2. Unbelievers possess their goods unjustly in so far as they are ordered by the laws of earthly princes to forfeit those goods. Hence these may be taken violently from them, not by private but by public authority.
3. It is no robbery if princes exact from their subjects that which is due to them for the safe-guarding of the common good, even if they use violence in so doing: but if they extort something unduly by means of violence, it is robbery even as burglary is. Hence Augustine says (De Civ. Dei iv, 4): "If justice be disregarded, what is a king but a mighty robber? since what is a robber but a little king?" And it is written (Ez 22,27): "Her princes in the midst of her, are like wolves ravening the prey." Wherefore they are bound to restitution, just as robbers are, and by so much do they sin more grievously than robbers, as their actions are fraught with greater and more universal danger to public justice whose wardens they are.
Summa Th. II-II EN Qu.65 a.3