Summa Th. II-II EN Qu.40
We must now consider war, under which head there are four points of inquiry:
(1) Whether some kind of war is lawful?
(2) Whether it is lawful for clerics to fight?
(3) Whether it is lawful for belligerents to lay ambushes?
(4) Whether it is lawful to fight on holy days?
Objection: 1. It would seem that it is always sinful to wage war. Because punishment is not inflicted except for sin. Now those who wage war are threatened by Our Lord with punishment, according to Mt 26,52: "All that take the sword shall perish with the sword." Therefore all wars are unlawful.
2. Further, whatever is contrary to a Divine precept is a sin. But war is contrary to a Divine precept, for it is written (Mt 5,39): "But I say to you not to resist evil"; and (Rm 12,19): "Not revenging yourselves, my dearly beloved, but give place unto wrath." Therefore war is always sinful.
3. Further, nothing, except sin, is contrary to an act of virtue. But war is contrary to peace. Therefore war is always a sin.
4. Further, the exercise of a lawful thing is itself lawful, as is evident in scientific exercises. But warlike exercises which take place in tournaments are forbidden by the Church, since those who are slain in these trials are deprived of ecclesiastical burial. Therefore it seems that war is a sin in itself.
On the contrary Augustine says in a sermon on the son of the centurion [*Ep. ad Marcel. cxxxviii]: "If the Christian Religion forbade war altogether, those who sought salutary advice in the Gospel would rather have been counselled to cast aside their arms, and to give up soldiering altogether. On the contrary, they were told: 'Do violence to no man . . . and be content with your pay' [*Lc 3,14]. If he commanded them to be content with their pay, he did not forbid soldiering."
I answer that In order for a war to be just, three things are necessary. First, the authority of the sovereign by whose command the war is to be waged. For it is not the business of a private individual to declare war, because he can seek for redress of his rights from the tribunal of his superior. Moreover it is not the business of a private individual to summon together the people, which has to be done in wartime. And as the care of the common weal is committed to those who are in authority, it is their business to watch over the common weal of the city, kingdom or province subject to them. And just as it is lawful for them to have recourse to the sword in defending that common weal against internal disturbances, when they punish evil-doers, according to the words of the Apostle (Rm 13,4): "He beareth not the sword in vain: for he is God's minister, an avenger to execute wrath upon him that doth evil"; so too, it is their business to have recourse to the sword of war in defending the common weal against external enemies. Hence it is said to those who are in authority (Ps 81,4): "Rescue the poor: and deliver the needy out of the hand of the sinner"; and for this reason Augustine says (Contra Faust. xxii, 75): "The natural order conducive to peace among mortals demands that the power to declare and counsel war should be in the hands of those who hold the supreme authority."Secondly, a just cause is required, namely that those who are attacked, should be attacked because they deserve it on account of some fault. Wherefore Augustine says (Questions. in Hept., qu. x, super ): "A just war is wont to be described as one that avenges wrongs, when a nation or state has to be punished, for refusing to make amends for the wrongs inflicted by its subjects, or to restore what it has seized unjustly."Thirdly, it is necessary that the belligerents should have a rightful intention, so that they intend the advancement of good, or the avoidance of evil. Hence Augustine says (De Verb. Dom. [*The words quoted are to be found not in St. Augustine's works, but Can. Apud. Caus. xxiii, qu. 1]): "True religion looks upon as peaceful those wars that are waged not for motives of aggrandizement, or cruelty, but with the object of securing peace, of punishing evil-doers, and of uplifting the good." For it may happen that the war is declared by the legitimate authority, and for a just cause, and yet be rendered unlawful through a wicked intention. Hence Augustine says (Contra Faust. xxii, 74): "The passion for inflicting harm, the cruel thirst for vengeance, an unpacific and relentless spirit, the fever of revolt, the lust of power, and such like things, all these are rightly condemned in war."
Reply to Objection: 1. As Augustine says (Contra Faust. xxii, 70): "To take the sword is to arm oneself in order to take the life of anyone, without the command or permission of superior or lawful authority." On the other hand, to have recourse to the sword (as a private person) by the authority of the sovereign or judge, or (as a public person) through zeal for justice, and by the authority, so to speak, of God, is not to "take the sword," but to use it as commissioned by another, wherefore it does not deserve punishment. And yet even those who make sinful use of the sword are not always slain with the sword, yet they always perish with their own sword, because, unless they repent, they are punished eternally for their sinful use of the sword.
2. Such like precepts, as Augustine observes (De Serm. Dom. in Monte i, 19), should always be borne in readiness of mind, so that we be ready to obey them, and, if necessary, to refrain from resistance or self-defense. Nevertheless it is necessary sometimes for a man to act otherwise for the common good, or for the good of those with whom he is fighting. Hence Augustine says (Ep ad Marcellin. cxxxviii): "Those whom we have to punish with a kindly severity, it is necessary to handle in many ways against their will. For when we are stripping a man of the lawlessness of sin, it is good for him to be vanquished, since nothing is more hopeless than the happiness of sinners, whence arises a guilty impunity, and an evil will, like an internal enemy."
3. Those who wage war justly aim at peace, and so they are not opposed to peace, except to the evil peace, which Our Lord "came not to send upon earth" (Mt 10,34). Hence Augustine says (Ep ad Bonif. clxxxix): "We do not seek peace in order to be at war, but we go to war that we may have peace. Be peaceful, therefore, in warring, so that you may vanquish those whom you war against, and bring them to the prosperity of peace."
4. Manly exercises in warlike feats of arms are not all forbidden, but those which are inordinate and perilous, and end in slaying or plundering. In olden times warlike exercises presented no such danger, and hence they were called "exercises of arms" or "bloodless wars," as Jerome states in an epistle [*Reference incorrect: cf. Veget., De Re Milit. i].
Objection: 1. It would seem lawful for clerics and bishops to fight. For, as stated above (Article [1]), wars are lawful and just in so far as they protect the poor and the entire common weal from suffering at the hands of the foe. Now this seems to be above all the duty of prelates, for Gregory says (Hom. in Ev. xiv): "The wolf comes upon the sheep, when any unjust and rapacious man oppresses those who are faithful and humble. But he who was thought to be the shepherd, and was not, leaveth the sheep, end flieth, for he fears lest the wolf hurt him, and dares not stand up against his injustice." Therefore it is lawful for prelates and clerics to fight.
2. Further, Pope Leo IV writes (xxiii, qu. 8, can. Igitur): "As untoward tidings had frequently come from the Saracen side, some said that the Saracens would come to the port of Rome secretly and covertly; for which reason we commanded our people to gather together, and ordered them to go down to the seashore." Therefore it is lawful for bishops to fight.
3. Further, apparently, it comes to the same whether a man does a thing himself, or consents to its being done by another, according to Rm 1,32: "They who do such things, are worthy of death, and not only they that do them, but they also that consent to them that do them." Now those, above all, seem to consent to a thing, who induce others to do it. But it is lawful for bishops and clerics to induce others to fight: for it is written (xxiii, qu. 8, can. Hortatu) that Charles went to war with the Lombards at the instance and entreaty of Adrian, bishop of Rome. Therefore they also are allowed to fight.
4. Further, whatever is right and meritorious in itself, is lawful for prelates and clerics. Now it is sometimes right and meritorious to make war, for it is written (xxiii, qu. 8, can. Omni timore) that if "a man die for the true faith, or to save his country, or in defense of Christians, God will give him a heavenly reward." Therefore it is lawful for bishops and clerics to fight.
On the contrary It was said to Peter as representing bishops and clerics (Mt 16,52): "Put up again thy sword into the scabbard [Vulg.: 'its place'] [*"Scabbard" is the reading in Jn 18,11]." Therefore it is not lawful for them to fight.
I answer that Several things are requisite for the good of a human society: and a number of things are done better and quicker by a number of persons than by one, as the Philosopher observes (Polit. i, 1), while certain occupations are so inconsistent with one another, that they cannot be fittingly exercised at the same time; wherefore those who are deputed to important duties are forbidden to occupy themselves with things of small importance. Thus according to human laws, soldiers who are deputed to warlike pursuits are forbidden to engage in commerce [*Cod. xii, 35, De Re Milit.].Now warlike pursuits are altogether incompatible with the duties of a bishop and a cleric, for two reasons. The first reason is a general one, because, to wit, warlike pursuits are full of unrest, so that they hinder the mind very much from the contemplation of Divine things, the praise of God, and prayers for the people, which belong to the duties of a cleric. Wherefore just as commercial enterprises are forbidden to clerics, because they unsettle the mind too much, so too are warlike pursuits, according to 2Tm 2,4: "No man being a soldier to God, entangleth himself with secular business." The second reason is a special one, because, to wit, all the clerical Orders are directed to the ministry of the altar, on which the Passion of Christ is represented sacramentally, according to 1Co 11,26: "As often as you shall eat this bread, and drink the chalice, you shall show the death of the Lord, until He come." Wherefore it is unbecoming for them to slay or shed blood, and it is more fitting that they should be ready to shed their own blood for Christ, so as to imitate in deed what they portray in their ministry. For this reason it has been decreed that those who shed blood, even without sin, become irregular. Now no man who has a certain duty to perform, can lawfully do that which renders him unfit for that duty. Wherefore it is altogether unlawful for clerics to fight, because war is directed to the shedding of blood.
Reply to Objection: 1. Prelates ought to withstand not only the wolf who brings spiritual death upon the flock, but also the pillager and the oppressor who work bodily harm; not, however, by having recourse themselves to material arms, but by means of spiritual weapons, according to the saying of the Apostle (2Co 10,4): "The weapons of our warfare are not carnal, but mighty through God." Such are salutary warnings, devout prayers, and, for those who are obstinate, the sentence of excommunication.
2. Prelates and clerics may, by the authority of their superiors, take part in wars, not indeed by taking up arms themselves, but by affording spiritual help to those who fight justly, by exhorting and absolving them, and by other like spiritual helps. Thus in the Old Testament (Jos 6,4) the priests were commanded to sound the sacred trumpets in the battle. It was for this purpose that bishops or clerics were first allowed to go to the front: and it is an abuse of this permission, if any of them take up arms themselves.
3. As stated above (Question [23], Article [4], ad 2) every power, art or virtue that regards the end, has to dispose that which is directed to the end. Now, among the faithful, carnal wars should be considered as having for their end the Divine spiritual good to which clerics are deputed. Wherefore it is the duty of clerics to dispose and counsel other men to engage in just wars. For they are forbidden to take up arms, not as though it were a sin, but because such an occupation is unbecoming their personality.
4. Although it is meritorious to wage a just war, nevertheless it is rendered unlawful for clerics, by reason of their being deputed to works more meritorious still. Thus the marriage act may be meritorious; and yet it becomes reprehensible in those who have vowed virginity, because they are bound to a yet greater good.
Objection: 1. It would seem that it is unlawful to lay ambushes in war. For it is written (Dt 16,20): "Thou shalt follow justly after that which is just." But ambushes, since they are a kind of deception, seem to pertain to injustice. Therefore it is unlawful to lay ambushes even in a just war.
2. Further, ambushes and deception seem to be opposed to faithfulness even as lies are. But since we are bound to keep faith with all men, it is wrong to lie to anyone, as Augustine states (Contra Mend. xv). Therefore, as one is bound to keep faith with one's enemy, as Augustine states (Ep ad Bonif. clxxxix), it seems that it is unlawful to lay ambushes for one's enemies.
3. Further, it is written (Mt 7,12): "Whatsoever you would that men should do to you, do you also to them": and we ought to observe this in all our dealings with our neighbor. Now our enemy is our neighbor. Therefore, since no man wishes ambushes or deceptions to be prepared for himself, it seems that no one ought to carry on war by laying ambushes.
On the contrary Augustine says (Questions. in Hept. qu. x super Jos): "Provided the war be just, it is no concern of justice whether it be carried on openly or by ambushes": and he proves this by the authority of the Lord, Who commanded Joshua to lay ambushes for the city of Hai (Jos 8,2).
I answer that The object of laying ambushes is in order to deceive the enemy. Now a man may be deceived by another's word or deed in two ways.First, through being told something false, or through the breaking of a promise, and this is always unlawful. No one ought to deceive the enemy in this way, for there are certain "rights of war and covenants, which ought to be observed even among enemies," as Ambrose states (De Officiis i).Secondly, a man may be deceived by what we say or do, because we do not declare our purpose or meaning to him. Now we are not always bound to do this, since even in the Sacred Doctrine many things have to be concealed, especially from unbelievers, lest they deride it, according to Mt 7,6: "Give not that which is holy, to dogs." Wherefore much more ought the plan of campaign to be hidden from the enemy. For this reason among other things that a soldier has to learn is the art of concealing his purpose lest it come to the enemy's knowledge, as stated in the Book on Strategy [*Stratagematum i, 1] by Frontinus. Such like concealment is what is meant by an ambush which may be lawfully employed in a just war.Nor can these ambushes be properly called deceptions, nor are they contrary to justice or to a well-ordered will. For a man would have an inordinate will if he were unwilling that others should hide anything from him
Reply to Objection: 1. This suffices for the Replies to the Objections.
Objection: 1. It would seem unlawful to fight on holy days. For holy days are instituted that we may give our time to the things of God. Hence they are included in the keeping of the Sabbath prescribed Ex 20,8: for "sabbath" is interpreted "rest." But wars are full of unrest. Therefore by no means is it lawful to fight on holy days.
2. Further, certain persons are reproached (Is 58,3) because on fast-days they exacted what was owing to them, were guilty of strife, and of smiting with the fist. Much more, therefore, is it unlawful to fight on holy days.
3. Further, no ill deed should be done to avoid temporal harm. But fighting on a holy day seems in itself to be an ill deed. Therefore no one should fight on a holy day even through the need of avoiding temporal harm.
On the contrary It is written (1 Machab 2:41): The Jews rightly determined . . . saying: "Whosoever shall come up against us to fight on the Sabbath-day, we will fight against him."
I answer that The observance of holy days is no hindrance to those things which are ordained to man's safety, even that of his body. Hence Our Lord argued with the Jews, saying (Jn 7,23): "Are you angry at Me because I have healed the whole man on the Sabbath-day?" Hence physicians may lawfully attend to their patients on holy days. Now there is much more reason for safeguarding the common weal (whereby many are saved from being slain, and innumerable evils both temporal and spiritual prevented), than the bodily safety of an individual. Therefore, for the purpose of safeguarding the common weal of the faithful, it is lawful to carry on a war on holy days, provided there be need for doing so: because it would be to tempt God, if notwithstanding such a need, one were to choose to refrain from fighting.However, as soon as the need ceases, it is no longer lawful to fight on a holy day, for the reasons given:
Reply to Objection: 1. wherefore this suffices for the Replies to the Objections.
We must now consider strife, under which head there are two points of inquiry:
(1) Whether strife is a sin?
(2) Whether it is a daughter of anger?
Objection: 1. It would seem that strife is not always a sin. For strife seems a kind of contention: hence Isidore says (Etym. x) that the word "rixosus [quarrelsome] is derived from the snarling [rictu] of a dog, because the quarrelsome man is ever ready to contradict; he delights in brawling, and provokes contention." Now contention is not always a sin. Neither, therefore, is strife.
2. Further, it is related (Gn 26,21) that the servants of Isaac "digged" another well, "and for that they quarrelled likewise." Now it is not credible that the household of Isaac quarrelled publicly, without being reproved by him, supposing it were a sin. Therefore strife is not a sin.
3. Further, strife seems to be a war between individuals. But war is not always sinful. Therefore strife is not always a sin.
On the contrary Strifes [*The Douay version has 'quarrels'] are reckoned among the works of the flesh (Ga 5,20), and "they who do such things shall not obtain the kingdom of God." Therefore strifes are not only sinful, but they are even mortal sins.
I answer that While contention implies a contradiction of words, strife denotes a certain contradiction of deeds. Wherefore a gloss on Ga 5,20 says that "strifes are when persons strike one another through anger." Hence strife is a kind of private war, because it takes place between private persons, being declared not by public authority, but rather by an inordinate will. Therefore strife is always sinful. In fact it is a mortal sin in the man who attacks another unjustly, for it is not without mortal sin that one inflicts harm on another even if the deed be done by the hands. But in him who defends himself, it may be without sin, or it may sometimes involve a venial sin, or sometimes a mortal sin; and this depends on his intention and on his manner of defending himself. For if his sole intention be to withstand the injury done to him, and he defend himself with due moderation, it is no sin, and one cannot say properly that there is strife on his part. But if, on the other hand, his self-defense be inspired by vengeance and hatred, it is always a sin. It is a venial sin, if a slight movement of hatred or vengeance obtrude itself, or if he does not much exceed moderation in defending himself: but it is a mortal sin if he makes for his assailant with the fixed intention of killing him, or inflicting grievous harm on him.
Reply to Objection: 1. Strife is not just the same as contention: and there are three things in the passage quoted from Isidore, which express the inordinate nature of strife. First, the quarrelsome man is always ready to fight, and this is conveyed by the words, "ever ready to contradict," that is to say, whether the other man says or does well or ill. Secondly, he delights in quarrelling itself, and so the passage proceeds, "and delights in brawling." Thirdly, "he" provokes others to quarrel, wherefore it goes on, "and provokes contention."
2. The sense of the text is not that the servants of Isaac quarrelled, but that the inhabitants of that country quarrelled with them: wherefore these sinned, and not the servants of Isaac, who bore the calumny [*Cf. Gn 26,20].
3. In order for a war to be just it must be declared by authority of the governing power, as stated above (Question [40], Article [1]); whereas strife proceeds from a private feeling of anger or hatred. For if the servants of a sovereign or judge, in virtue of their public authority, attack certain men and these defend themselves, it is not the former who are said to be guilty of strife, but those who resist the public authority. Hence it is not the assailants in this case who are guilty of strife and commit sin, but those who defend themselves inordinately.
Objection: 1. It would seem that strife is not a daughter of anger. For it is written (Jc 4,1): "Whence are wars and contentions? Are they not . . . from your concupiscences, which war in your members?" But anger is not in the concupiscible faculty. Therefore strife is a daughter, not of anger, but of concupiscence.
2. Further, it is written (Pr 28,25): "He that boasteth and puffeth up himself, stirreth up quarrels." Now strife is apparently the same as quarrel. Therefore it seems that strife is a daughter of pride or vainglory which makes a man boast and puff himself up.
3. Further, it is written (Pr 18,6): "The lips of a fool intermeddle with strife." Now folly differs from anger, for it is opposed, not to meekness, but to wisdom or prudence. Therefore strife is not a daughter of anger.
4. Further, it is written (Pr 10,12): "Hatred stirreth up strifes." But hatred arises from envy, according to Gregory (Moral. xxxi, 17). Therefore strife is not a daughter of anger, but of envy.
5. Further, it is written (Pr 17,19): "He that studieth discords, soweth [Vulg.: 'loveth'] quarrels." But discord is a daughter of vainglory, as stated above (Question [37], Article [2]). Therefore strife is also.
On the contrary Gregory says (Moral. xxxi, 17) that "anger gives rise to strife"; and it is written (Pr 15,18 Pr 29,22): "A passionate man stirreth up strifes."
I answer that As stated above (Article [1]), strife denotes an antagonism extending to deeds, when one man designs to harm another. Now there are two ways in which one man may intend to harm another. In one way it is as though he intended absolutely the other's hurt, which in this case is the outcome of hatred, for the intention of hatred is directed to the hurt of one's enemy either openly or secretly. In another way a man intends to hurt another who knows and withstands his intention. This is what we mean by strife, and belongs properly to anger which is the desire of vengeance: for the angry man is not content to hurt secretly the object of his anger, he even wishes him to feel the hurt and know that what he suffers is in revenge for what he has done, as may be seen from what has been said above about the passion of anger (FS, Question [46], Article [6], ad 2). Therefore, properly speaking, strife arises from anger.
Reply to Objection: 1. As stated above (FS, Question [25], Articles [1],2), all the irascible passions arise from those of the concupiscible faculty, so that whatever is the immediate outcome of anger, arises also from concupiscence as from its first root.
2. Boasting and puffing up of self which are the result of anger or vainglory, are not the direct but the occasional cause of quarrels or strife, because, when a man resents another being preferred to him, his anger is aroused, and then his anger results in quarrel and strife.
3. Anger, as stated above (FS, Question [48], Article [3]) hinders the judgment of the reason, so that it bears a likeness to folly. Hence they have a common effect, since it is due to a defect in the reason that a man designs to hurt another inordinately.
4. Although strife sometimes arises from hatred, it is not the proper effect thereof, because when one man hates another it is beside his intention to hurt him in a quarrelsome and open manner, since sometimes he seeks to hurt him secretly. When, however, he sees himself prevailing, he endeavors to harm him with strife and quarrel. But to hurt a man in a quarrel is the proper effect of anger, for the reason given above.
5. Strifes give rise to hatred and discord in the hearts of those who are guilty of strife, and so he that "studies," i.e., intends to sow discord among others, causes them to quarrel among themselves. Even so any sin may command the act of another sin, by directing it to its own end. This does not, however, prove that strife is the daughter of vainglory properly and directly.
We must now consider sedition, under which head there are two points of inquiry:
(1) Whether it is a special sin?
(2) Whether it is a mortal sin?
Objection: 1. It would seem that sedition is not a special sin distinct from other sins. For, according to Isidore (Etym. x), "a seditious man is one who sows dissent among minds, and begets discord." Now, by provoking the commission of a sin, a man sins by no other kind of sin than that which he provoked. Therefore it seems that sedition is not a special sin distinct from discord.
2. Further, sedition denotes a kind of division. Now schism takes its name from scission, as stated above (Question [39], Article [1]). Therefore, seemingly, the sin of sedition is not distinct from that of schism.
3. Further, every special sin that is distinct from other sins, is either a capital vice, or arises from some capital vice. Now sedition is reckoned neither among the capital vices, nor among those vices which arise from them, as appears from Moral. xxxi, 45, where both kinds of vice are enumerated. Therefore sedition is not a special sin, distinct from other sins.
On the contrary Seditions are mentioned as distinct from other sins (2Co 12,20).
I answer that Sedition is a special sin, having something in common with war and strife, and differing somewhat from them. It has something in common with them, in so far as it implies a certain antagonism, and it differs from them in two points. First, because war and strife denote actual aggression on either side, whereas sedition may be said to denote either actual aggression, or the preparation for such aggression. Hence a gloss on 2Co 12,20 says that "seditions are tumults tending to fight," when, to wit, a number of people make preparations with the intention of fighting. Secondly, they differ in that war is, properly speaking, carried on against external foes, being as it were between one people and another, whereas strife is between one individual and another, or between few people on one side and few on the other side, while sedition, in its proper sense, is between mutually dissentient parts of one people, as when one part of the state rises in tumult against another part. Wherefore, since sedition is opposed to a special kind of good, namely the unity and peace of a people, it is a special kind of sin.
Reply to Objection: 1. A seditious man is one who incites others to sedition, and since sedition denotes a kind of discord, it follows that a seditious man is one who creates discord, not of any kind, but between the parts of a multitude. And the sin of sedition is not only in him who sows discord, but also in those who dissent from one another inordinately.
2. Sedition differs from schism in two respects. First, because schism is opposed to the spiritual unity of the multitude, viz. ecclesiastical unity, whereas sedition is contrary to the temporal or secular unity of the multitude, for instance of a city or kingdom. Secondly, schism does not imply any preparation for a material fight as sedition does, but only for a spiritual dissent.
3. Sedition, like schism, is contained under discord, since each is a kind of discord, not between individuals, but between the parts of a multitude.
Objection: 1. It would seem that sedition is not always a mortal sin. For sedition denotes "a tumult tending to fight," according to the gloss quoted above (Article [1]). But fighting is not always a mortal sin, indeed it is sometimes just and lawful, as stated above (Question [40], Article [1]). Much more, therefore, can sedition be without a mortal sin.
2. Further, sedition is a kind of discord, as stated above (Article [1], ad 3). Now discord can be without mortal sin, and sometimes without any sin at all. Therefore sedition can be also.
3. Further, it is praiseworthy to deliver a multitude from a tyrannical rule. Yet this cannot easily be done without some dissension in the multitude, if one part of the multitude seeks to retain the tyrant, while the rest strive to dethrone him. Therefore there can be sedition without mortal sin.
On the contrary The Apostle forbids seditions together with other things that are mortal sins (2Co 12,20).
I answer that As stated above (Article [1], ad 2), sedition is contrary to the unity of the multitude, viz. the people of a city or kingdom. Now Augustine says (De Civ. Dei ii, 21) that "wise men understand the word people to designate not any crowd of persons, but the assembly of those who are united together in fellowship recognized by law and for the common good." Wherefore it is evident that the unity to which sedition is opposed is the unity of law and common good: whence it follows manifestly that sedition is opposed to justice and the common good. Therefore by reason of its genus it is a mortal sin, and its gravity will be all the greater according as the common good which it assails surpasses the private good which is assailed by strife.Accordingly the sin of sedition is first and chiefly in its authors, who sin most grievously; and secondly it is in those who are led by them to disturb the common good. Those, however, who defend the common good, and withstand the seditious party, are not themselves seditious, even as neither is a man to be called quarrelsome because he defends himself, as stated above (Question [41], Article [1]).
Reply to Objection: 1. It is lawful to fight, provided it be for the common good, as stated above (Question [40], Article [1]). But sedition runs counter to the common good of the multitude, so that it is always a mortal sin.
2. Discord from what is not evidently good, may be without sin, but discord from what is evidently good, cannot be without sin: and sedition is discord of this kind, for it is contrary to the unity of the multitude, which is a manifest good.
3. A tyrannical government is not just, because it is directed, not to the common good, but to the private good of the ruler, as the Philosopher states (Polit. iii, 5; Ethic. viii, 10). Consequently there is no sedition in disturbing a government of this kind, unless indeed the tyrant's rule be disturbed so inordinately, that his subjects suffer greater harm from the consequent disturbance than from the tyrant's government. Indeed it is the tyrant rather that is guilty of sedition, since he encourages discord and sedition among his subjects, that he may lord over them more securely; for this is tyranny, being conducive to the private good of the ruler, and to the injury of the multitude.
Summa Th. II-II EN Qu.40