Summa Th. II-II EN Qu.37


We must now consider the sins contrary to peace, and first we shall consider discord which is in the heart, secondly contention, which is on the lips, thirdly, those things which consist in deeds, viz. schism, quarrelling, war, and sedition. Under the first head there are two points of inquiry:

(1) Whether discord is a sin?

(2) Whether it is a daughter of vainglory?

Whether discord is a sin?

Objection: 1. It would seem that discord is not a sin. For to disaccord with man is to sever oneself from another's will. But this does not seem to be a sin, because God's will alone, and not our neighbor's, is the rule of our own will. Therefore discord is not a sin.
2. Further, whoever induces another to sin, sins also himself. But it appears not to be a sin to incite others to discord, for it is written (Ac 23,6) that Paul, knowing that the one part were Sadducees, and the other Pharisees, cried out in the council: "Men brethren, I am a Pharisee, the son of Pharisees, concerning the hope and resurrection of the dead I am called in question. And when he had so said, there arose a dissension between the Pharisees and the Sadducees." Therefore discord is not a sin.
3. Further, sin, especially mortal sin, is not to be found in a holy man. But discord is to be found even among holy men, for it is written (Ac 15,39): "There arose a dissension" between Paul and Barnabas, "so that they departed one from another." Therefore discord is not a sin. and least of all a mortal sin.

On the contrary "Dissensions," that is, discords, are reckoned among the works of the flesh (Ga 5,20), of which it is said afterwards (Ga 5,21) that "they who do such things shall not obtain the kingdom of God." Now nothing, save mortal sin, excludes man from the kingdom of God. Therefore discord is a mortal sin.
I answer that Discord is opposed to concord. Now, as stated above (Question [29], Articles [1],3) concord results from charity, in as much as charity directs many hearts together to one thing, which is chiefly the Divine good, secondarily, the good of our neighbor. Wherefore discord is a sin, in so far as it is opposed to this concord.But it must be observed that this concord is destroyed by discord in two ways: first, directly; secondly, accidentally. Now, human acts and movements are said to be direct when they are according to one's intention. Wherefore a man directly disaccords with his neighbor, when he knowingly and intentionally dissents from the Divine good and his neighbor's good, to which he ought to consent. This is a mortal sin in respect of its genus, because it is contrary to charity, although the first movements of such discord are venial sins by reason of their being imperfect acts.The accidental in human acts is that which occurs beside the intention. Hence when several intend a good pertaining to God's honor, or our neighbor's profit, while one deems a certain thing good, and another thinks contrariwise, the discord is in this case accidentally contrary to the Divine good or that of our neighbor. Such like discord is neither sinful nor against charity, unless it be accompanied by an error about things necessary to salvation, or by undue obstinacy, since it has also been stated above (Question [29], Articles [1],3, ad 2) that the concord which is an effect of charity, is union of wills not of opinions. It follows from this that discord is sometimes the sin of one party only, for instance, when one wills a good which the other knowingly resists; while sometimes it implies sin in both parties, as when each dissents from the other's good, and loves his own.

Reply to Objection: 1. One man's will considered in itself is not the rule of another man's will; but in so far as our neighbor's will adheres to God's will, it becomes in consequence, a rule regulated according to its proper measure. Wherefore it is a sin to disaccord with such a will, because by that very fact one disaccords with the Divine rule.
2. Just as a man's will that adheres to God is a right rule, to disaccord with which is a sin, so too a man's will that is opposed to God is a perverse rule, to disaccord with which is good. Hence to cause a discord, whereby a good concord resulting from charity is destroyed, is a grave sin: wherefore it is written (Pr 6,16): "Six things there are, which the Lord hateth, and the seventh His soul detesteth," which seventh is stated (Pr 6,19) to be "him that soweth discord among brethren." On the other hand, to arouse a discord whereby an evil concord (i.e. concord in an evil will) is destroyed, is praiseworthy. In this way Paul was to be commended for sowing discord among those who concorded together in evil, because Our Lord also said of Himself (Mt 10,34): "I came not to send peace, but the sword."
3. The discord between Paul and Barnabas was accidental and not direct: because each intended some good, yet the one thought one thing good, while the other thought something else, which was owing to human deficiency: for that controversy was not about things necessary to salvation. Moreover all this was ordained by Divine providence, on account of the good which would ensue.

Whether discord is a daughter of vainglory?

Objection: 1. It would seem that discord is not a daughter of vainglory. For anger is a vice distinct from vainglory. Now discord is apparently the daughter of anger, according to Pr 15,18: "A passionate man stirreth up strifes." Therefore it is not a daughter of vainglory.
2. Further, Augustine expounding the words of Jn 7,39, "As yet the Spirit was not given," says (Tract. xxxii) "Malice severs, charity unites." Now discord is merely a separation of wills. Therefore discord arises from malice, i.e. envy, rather than from vainglory.
3. Further, whatever gives rise to many evils, would seem to be a capital vice. Now such is discord, because Jerome in commenting on Mt 12,25, "Every kingdom divided against itself shall be made desolate," says: "Just as concord makes small things thrive, so discord brings the greatest things to ruin." Therefore discord should itself be reckoned a capital vice, rather than a daughter of vainglory.

On the contrary On the contrary stands the authority of Gregory (Moral. xxxi, 45).
I answer that Discord denotes a certain disunion of wills, in so far, to wit, as one man's will holds fast to one thing, while the other man's will holds fast to something else. Now if a man's will holds fast to its own ground, this is due to the act that he prefers what is his own to that which belongs to others, and if he do this inordinately, it is due to pride and vainglory. Therefore discord, whereby a man holds to his own way of thinking, and departs from that of others, is reckoned to be a daughter of vainglory.

Reply to Objection: 1. Strife is not the same as discord, for strife consists in external deeds, wherefore it is becoming that it should arise from anger, which incites the mind to hurt one's neighbor; whereas discord consists in a divergence in the movements of wills, which arises from pride or vainglory, for the reason given above.
2. In discord we may consider that which is the term "wherefrom," i.e. another's will from which we recede, and in this respect it arises from envy; and again we may consider that which is the term "whither," i.e. something of our own to which we cling, and in this respect it is caused by vainglory. And since in every moment the term "whither" is more important than the term "wherefrom" (because the end is of more account than the beginning), discord is accounted a daughter of vainglory rather than of envy, though it may arise from both for different reasons, as stated.
3. The reason why concord makes small things thrive, while discord brings the greatest to ruin, is because "the more united a force is, the stronger it is, while the more disunited it is the weaker it becomes" (De Causis xvii). Hence it is evident that this is part of the proper effect of discord which is a disunion of wills, and in no way indicates that other vices arise from discord, as though it were a capital vice.


We must now consider contention, in respect of which there are two points of inquiry:

(1) Whether contention is a mortal sin?

(2) Whether it is a daughter of vainglory?

Whether contention is a mortal sin?

Objection: 1. It would seem that contention is not a mortal sin. For there is no mortal sin in spiritual men: and yet contention is to be found in them, according to Lc 22,24: "And there was also a strife amongst" the disciples of Jesus, "which of them should . . . be the greatest." Therefore contention is not a mortal sin.
2. Further, no well disposed man should be pleased that his neighbor commit a mortal sin. But the Apostle says (Ph 1,17): "Some out of contention preach Christ," and afterwards he says (Ph 1,18): "In this also I rejoice, yea, and will rejoice." Therefore contention is not a mortal sin.
3. Further, it happens that people contend either in the courts or in disputations, without any spiteful purpose, and with a good intention, as, for example, those who contend by disputing with heretics. Hence a gloss on 1S 14,1, "It came to pass one day," etc. says: "Catholics do not raise contentions with heretics, unless they are first challenged to dispute." Therefore contention is not a mortal sin.
4. Further, Job seems to have contended with God, according to Jb 39,32: "Shall he that contendeth with God be so easily silenced?" And yet Job was not guilty of mortal sin, since the Lord said of him (Jb 42,7): "You have not spoken the thing that is right before me, as my servant Job hath." Therefore contention is not always a mortal sin.

On the contrary It is against the precept of the Apostle who says (2Tm 2,14): "Contend not in words." Moreover (Ga 5,20) contention is included among the works of the flesh, and as stated there (Ga 5,21) "they who do such things shall not obtain the kingdom of God." Now whatever excludes a man from the kingdom of God and is against a precept, is a mortal sin. Therefore contention is a mortal sin.
I answer that To contend is to tend against some one. Wherefore just as discord denotes a contrariety of wills, so contention signifies contrariety of speech. For this reason when a man contrasts various contrary things in a speech, this is called "contentio," which Tully calls one of the rhetorical colors (De Rhet. ad Heren. iv), where he says that "it consists in developing a speech from contrary things," for instance: "Adulation has a pleasant beginning, and a most bitter end."Now contrariety of speech may be looked at in two ways: first with regard to the intention of the contentious party, secondly, with regard to the manner of contending. As to the intention, we must consider whether he contends against the truth, and then he is to be blamed, or against falsehood, and then he should be praised. As to the manner, we must consider whether his manner of contending is in keeping with the persons and the matter in dispute, for then it would be praiseworthy, hence Tully says (De Rhet. ad Heren. iii) that "contention is a sharp speech suitable for proof and refutation"---or whether it exceeds the demands of the persons and matter in dispute, in which case it is blameworthy.Accordingly if we take contention as denoting a disclaimer of the truth and an inordinate manner, it is a mortal sin. Thus Ambrose [*Cf. Gloss. Ord. in Rom. i, 29] defines contention: "Contention is a disclaimer of the truth with clamorous confidence." If, however, contention denote a disavowal of what is false, with the proper measure of acrimony, it is praiseworthy: whereas, if it denote a disavowal of falsehood, together with an inordinate manner, it can be a venial sin, unless the contention be conducted so inordinately, as to give scandal to others. Hence the Apostle after saying (2Tm 2,14): "Contend not in words," adds, "for it is to no profit, but to the subverting of the hearers."

Reply to Objection: 1. The disciples of Christ contended together, not with the intention of disclaiming the truth, since each one stood up for what he thought was true. Yet there was inordinateness in their contention, because they contended about a matter which they ought not to have contended about, viz. the primacy of honor; for they were not spiritual men as yet, as a gloss says on the same passage; and for this reason Our Lord checked them.
2. Those who preached Christ "out of contention," were to be blamed, because, although they did not gainsay the truth of faith, but preached it, yet they did gainsay the truth, by the fact that they thought they would "raise affliction" to the Apostle who was preaching the truth of faith. Hence the Apostle rejoiced not in their contention, but in the fruit that would result therefrom, namely that Christ would be made known---since evil is sometimes the occasion of good results.
3. Contention is complete and is a mortal sin when, in contending before a judge, a man gainsays the truth of justice, or in a disputation, intends to impugn the true doctrine. In this sense Catholics do not contend against heretics, but the reverse. But when, whether in court or in a disputation, it is incomplete, i.e. in respect of the acrimony of speech, it is not always a mortal sin.
4. Contention here denotes an ordinary dispute. For Job had said (Jb 13,3): "I will speak to the Almighty, and I desire to reason with God": yet he intended not to impugn the truth, but to defend it, and in seeking the truth thus, he had no wish to be inordinate in mind or in speech.

Whether contention is a daughter of vainglory?

Objection: 1. It would seem that contention is not a daughter of vainglory. For contention is akin to zeal, wherefore it is written (1Co 3,3): "Whereas there is among you zeal [Douay: 'envying'] and contention, are you not carnal, and walk according to men?" Now zeal pertains to envy. Therefore contention arises rather from envy.
2. Further, contention is accompanied by raising of the voice. But the voice is raised on account of anger, as Gregory declares (Moral. xxxi, 14). Therefore contention too arises from anger.
3. Further, among other things knowledge seems to be the matter of pride and vainglory, according to 1Co 8,1: "Knowledge puffeth up." Now contention is often due to lack of knowledge, and by knowledge we do not impugn the truth, we know it. Therefore contention is not a daughter of vainglory.

On the contrary On the contrary stands the authority of Gregory (Moral. xxxi, 14).
I answer that As stated above (Question [37], Article [2]), discord is a daughter of vainglory, because each of the disaccording parties clings to his own opinion, rather than acquiesce with the other. Now it is proper to pride and vainglory to seek one's own glory. And just as people are discordant when they hold to their own opinion in their hearts, so are they contentious when each defends his own opinion by words. Consequently contention is reckoned a daughter of vainglory for the same reason as discord.

Reply to Objection: 1. Contention, like discord, is akin to envy in so far as a man severs himself from the one with whom he is discordant, or with whom he contends, but in so far as a contentious man holds to something, it is akin to pride and vainglory, because, to wit, he clings to his own opinion, as stated above (Question [37], Article [2], ad 1).
2. The contention of which we are speaking puts on a loud voice, for the purpose of impugning the truth, so that it is not the chief part of contention. Hence it does not follow that contention arises from the same source as the raising of the voice.
3. Pride and vainglory are occasioned chiefly by goods even those that are contrary to them, for instance, when a man is proud of his humility: for when a thing arises in this way, it does so not directly but accidentally, in which way nothing hinders one contrary from arising out of another. Hence there is no reason why the "per se" and direct effects of pride or vainglory, should not result from the contraries of those things which are the occasion of pride.


We must now consider the vices contrary to peace, which belong to deeds: such are schism, strife, sedition, and war. In the first place, then, about schism, there are four points of inquiry:

(1) Whether schism is a special sin?

(2) Whether it is graver than unbelief?

(3) Of the power exercised by schismatics;

(4) Of the punishment inflicted on them.

Whether schism is a special sin?

Objection: 1. It would seem that schism is not a special sin. For "schism," as Pope Pelagius I says (Epist. ad Victor. et Pancrat.), "denotes a division." But every sin causes a division, according to Is 59: "Your sins have divided between you and your God." Therefore schism is not a special sin.
2. Further, a man is apparently a schismatic if he disobeys the Church. But every sin makes a man disobey the commandments of the Church, because sin, according to Ambrose (De Parad. viii) "is disobedience against the heavenly commandments." Therefore every sin is a schism.
3. Further, heresy also divides a man from the unity of faith. If, therefore, the word schism denotes a division, it would seem not to differ, as a special sin, from the sin of unbelief.

On the contrary Augustine (Contra Faust. xx, 3; Contra Crescon. ii, 4) distinguishes between schism and heresy, for he says that a "schismatic is one who holds the same faith, and practises the same worship, as others, and takes pleasure in the mere disunion of the community, whereas a heretic is one who holds another faith from that of the Catholic Church." Therefore schism is not a generic sin.
I answer that As Isidore says (Etym. viii, 3), schism takes its name "from being a scission of minds," and scission is opposed to unity. Wherefore the sin of schism is one that is directly and essentially opposed to unity. For in the moral, as in the physical order, the species is not constituted by that which is accidental. Now, in the moral order, the essential is that which is intended, and that which results beside the intention, is, as it were, accidental. Hence the sin of schism is, properly speaking, a special sin, for the reason that the schismatic intends to sever himself from that unity which is the effect of charity: because charity unites not only one person to another with the bond of spiritual love, but also the whole Church in unity of spirit.Accordingly schismatics properly so called are those who, wilfully and intentionally separate themselves from the unity of the Church; for this is the chief unity, and the particular unity of several individuals among themselves is subordinate to the unity of the Church, even as the mutual adaptation of each member of a natural body is subordinate to the unity of the whole body. Now the unity of the Church consists in two things; namely, in the mutual connection or communion of the members of the Church, and again in the subordination of all the members of the Church to the one head, according to Col 2,18-19: "Puffed up by the sense of his flesh, and not holding the Head, from which the whole body, by joints and bands, being supplied with nourishment and compacted, groweth unto the increase of God." Now this Head is Christ Himself, Whose viceregent in the Church is the Sovereign Pontiff. Wherefore schismatics are those who refuse to submit to the Sovereign Pontiff, and to hold communion with those members of the Church who acknowledge his supremacy.

Reply to Objection: 1. The division between man and God that results from sin is not intended by the sinner: it happens beside his intention as a result of his turning inordinately to a mutable good, and so it is not schism properly so called.
2. The essence of schism consists in rebelliously disobeying the commandments: and I say "rebelliously," since a schismatic both obstinately scorns the commandments of the Church, and refuses to submit to her judgment. But every sinner does not do this, wherefore not every sin is a schism.
3. Heresy and schism are distinguished in respect of those things to which each is opposed essentially and directly. For heresy is essentially opposed to faith, while schism is essentially opposed to the unity of ecclesiastical charity. Wherefore just as faith and charity are different virtues, although whoever lacks faith lacks charity, so too schism and heresy are different vices, although whoever is a heretic is also a schismatic, but not conversely. This is what Jerome says in his commentary on the Epistle to the Galatians [*In Ep. ad Tit. iii, 10]: "I consider the difference between schism and heresy to be that heresy holds false doctrine while schism severs a man from the Church." Nevertheless, just as the loss of charity is the road to the loss of faith, according to 1Tm 1,6: "From which things," i.e. charity and the like, "some going astray, are turned aside into vain babbling," so too, schism is the road to heresy. Wherefore Jerome adds (In Ep ad Tit. iii, 10) that "at the outset it is possible, in a certain respect, to find a difference between schism and heresy: yet there is no schism that does not devise some heresy for itself, that it may appear to have had a reason for separating from the Church."

Whether schism is a graver sin than unbelief?

Objection: 1. It would seem that schism is a graver sin than unbelief. For the graver sin meets with a graver punishment, according to Dt 25,2: "According to the measure of the sin shall the measure also of the stripes be." Now we find the sin of schism punished more severely than even the sin of unbelief or idolatry: for we read (Ex 32,28) that some were slain by the swords of their fellow men on account of idolatry: whereas of the sin of schism we read (Nb 16,30): "If the Lord do a new thing, and the earth opening her mouth swallow them down, and all things that belong to them, and they go down alive into hell, you shall know that they have blasphemed the Lord God." Moreover the ten tribes who were guilty of schism in revolting from the rule of David were most severely punished (2R 17,20). Therefore the sin of schism is graver than the sin of unbelief.
2. Further, "The good of the multitude is greater and more godlike than the good of the individual," as the Philosopher states (Ethic. i, 2). Now schism is opposed to the good of the multitude, namely, ecclesiastical unity, whereas unbelief is contrary to the particular good of one man, namely the faith of an individual. Therefore it seems that schism is a graver sin than unbelief.
3. Further, a greater good is opposed to a greater evil, according to the Philosopher (Ethic. viii, 10). Now schism is opposed to charity, which is a greater virtue than faith to which unbelief is opposed, as shown above (Question [10], Article [2]; Question [23], Article [6]). Therefore schism is a graver sin than unbelief.

On the contrary That which results from an addition to something else surpasses that thing either in good or in evil. Now heresy results from something being added to schism, for it adds corrupt doctrine, as Jerome declares in the passage quoted above (Article [1], ad 3). Therefore schism is a less grievous sin than unbelief.
I answer that The gravity of a sin can be considered in two ways: first, according to the species of that sin, secondly, according to its circumstances. And since particular circumstances are infinite in number, so too they can be varied in an infinite number of ways: wherefore if one were to ask in general which of two sins is the graver, the question must be understood to refer to the gravity derived from the sin's genus. Now the genus or species of a sin is taken from its object, as shown above (FS, Question [72], Article [1]; FS, Question [73], Article [3]). Wherefore the sin which is opposed to the greater good is, in respect of its genus, more grievous, for instance a sin committed against God is graver than a sin committed against one's neighbor.Now it is evident that unbelief is a sin committed against God Himself, according as He is Himself the First Truth, on which faith is founded; whereas schism is opposed to ecclesiastical unity, which is a participated good, and a lesser good than God Himself. Wherefore it is manifest that the sin of unbelief is generically more grievous than the sin of schism, although it may happen that a particular schismatic sins more grievously than a particular unbeliever, either because his contempt is greater, or because his sin is a source of greater danger, or for some similar reason.

Reply to Objection: 1. It had already been declared to that people by the law which they had received that there was one God, and that no other God was to be worshipped by them; and the same had been confirmed among them by many kinds of signs. Consequently there was no need for those who sinned against this faith by falling into idolatry, to be punished in an unwonted manner: it was enough that they should be punished in the usual way. On the other hand, it was not so well known among them that Moses was always to be their ruler, and so it behooved those who rebelled against his authority to be punished in a miraculous and unwonted manner.We may also reply by saying that the sin of schism was sometimes more severely punished in that people, because they were inclined to seditions and schisms. For it is written (1 Esdra 4:15): "This city since days gone by has rebelled against its kings: and seditions and wars were raised therein [*Vulg.: 'This city is a rebellious city, and hurtful to the kings and provinces, and . . . wars were raised therein of old']." Now sometimes a more severe punishment is inflicted for an habitual sin (as stated above, FS, Question [105], Article [2], ad 9), because punishments are medicines intended to keep man away from sin: so that where there is greater proneness to sin, a more severe punishment ought to be inflicted. As regards the ten tribes, they were punished not only for the sin of schism, but also for that of idolatry as stated in the passage quoted.
2. Just as the good of the multitude is greater than the good of a unit in that multitude, so is it less than the extrinsic good to which that multitude is directed, even as the good of a rank in the army is less than the good of the commander-in-chief. In like manner the good of ecclesiastical unity, to which schism is opposed, is less than the good of Divine truth, to which unbelief is opposed.
3. Charity has two objects; one is its principal object and is the Divine goodness, the other is its secondary object and is our neighbor's good. Now schism and other sins against our neighbor, are opposed to charity in respect of its secondary good, which is less than the object of faith, for this is God Himself; and so these sins are less grievous than unbelief. On the other hand, hatred of God, which is opposed to charity in respect of its principal object, is not less grievous than unbelief. Nevertheless of all sins committed by man against his neighbor, the sin of schism would seem to be the greatest, because it is opposed to the spiritual good of the multitude.

Whether schismatics have any power?

Objection: 1. It would seem that schismatics have some power. For Augustine says (Contra Donat. i, 1): "Just as those who come back to the Church after being baptized, are not baptized again, so those who return after being ordained, are not ordained again." Now Order is a kind of power. Therefore schismatics have some power since they retain their Orders.
2. Further, Augustine says (De Unico Bapt. [*De Bap. contra Donat. vi, 5]): "One who is separated can confer a sacrament even as he can have it." But the power of conferring a sacrament is a very great power. Therefore schismatics who are separated from the Church, have a spiritual power.
3. Further, Pope Urban II [*Council of Piacenza, cap. x; cf. Can. Ordinationes, ix, qu. 1] says: "We command that persons consecrated by bishops who were themselves consecrated according to the Catholic rite, but have separated themselves by schism from the Roman Church, should be received mercifully and that their Orders should be acknowledged, when they return to the unity of the Church, provided they be of commendable life and knowledge." But this would not be so, unless spiritual power were retained by schismatics. Therefore schismatics have spiritual power.

On the contrary Cyprian says in a letter (Ep. lii, quoted vii, qu. 1, can. Novatianus): "He who observes neither unity of spirit nor the concord of peace, and severs himself from the bonds of the Church, and from the fellowship of her priests, cannot have episcopal power or honor."
I answer that Spiritual power is twofold, the one sacramental, the other a power of jurisdiction. The sacramental power is one that is conferred by some kind of consecration. Now all the consecrations of the Church are immovable so long as the consecrated thing remains: as appears even in inanimate things, since an altar, once consecrated, is not consecrated again unless it has been broken up. Consequently such a power as this remains, as to its essence, in the man who has received it by consecration, as long as he lives, even if he fall into schism or heresy: and this is proved from the fact that if he come back to the Church, he is not consecrated anew. Since, however, the lower power ought not to exercise its act, except in so far as it is moved by the higher power, as may be seen also in the physical order, it follows that such persons lose the use of their power, so that it is not lawful for them to use it. Yet if they use it, this power has its effect in sacramental acts, because therein man acts only as God's instrument, so that sacramental effects are not precluded on account of any fault whatever in the person who confers the sacrament.On the other hand, the power of jurisdiction is that which is conferred by a mere human appointment. Such a power as this does not adhere to the recipient immovably: so that it does not remain in heretics and schismatics; and consequently they neither absolve nor excommunicate, nor grant indulgence, nor do anything of the kind, and if they do, it is invalid.Accordingly when it is said that such like persons have no spiritual power, it is to be understood as referring either to the second power, or if it be referred to the first power, not as referring to the essence of the power, but to its lawful use.

Reply to Objection: 1. This suffices for the Replies to the Objections.

Whether it is right that schismatics should be punished with excommunication?

Objection: 1. It would seem that schismatics are not rightly punished with excommunication. For excommunication deprives a man chiefly of a share in the sacraments. But Augustine says (Contra Donat. vi, 5) that "Baptism can be received from a schismatic." Therefore it seems that excommunication is not a fitting punishment for schismatics.
2. Further, it is the duty of Christ's faithful to lead back those who have gone astray, wherefore it is written against certain persons (Ez 34,4): "That which was driven away you have not brought again, neither have you sought that which was lost." Now schismatics are more easily brought back by such as may hold communion with them. Therefore it seems that they ought not to be excommunicated.
3. Further, a double punishment is not inflicted for one and the same sin, according to Nahum 1:9: "God will not judge the same twice" [*Septuagint version]. Now some receive a temporal punishment for the sin of schism, according to Question [23], Article [5], where it is stated: "Both divine and earthly laws have laid down that those who are severed from the unity of the Church, and disturb her peace, must be punished by the secular power." Therefore they ought not to be punished with excommunication.

On the contrary It is written (Nb 16,26): "Depart from the tents of these wicked men," those, to wit, who had caused the schism, "and touch nothing of theirs, lest you be involved in their sins."
I answer that According to Sg 11,11, "By what things a man sinneth, by the same also he should be punished" [Vulg.: 'he is tormented']. Now a schismatic, as shown above (Article [1]), commits a twofold sin: first by separating himself from communion with the members of the Church, and in this respect the fitting punishment for schismatics is that they be excommunicated. Secondly, they refuse submission to the head of the Church, wherefore, since they are unwilling to be controlled by the Church's spiritual power, it is just that they should be compelled by the secular power.

Reply to Objection: 1. It is not lawful to receive Baptism from a schismatic, save in a case of necessity, since it is better for a man to quit this life, marked with the sign of Christ, no matter from whom he may receive it, whether from a Jew or a pagan, than deprived of that mark, which is bestowed in Baptism.
2. Excommunication does not forbid the intercourse whereby a person by salutary admonitions leads back to the unity of the Church those who are separated from her. Indeed this very separation brings them back somewhat, because through confusion at their separation, they are sometimes led to do penance
3. The punishments of the present life are medicinal, and therefore when one punishment does not suffice to compel a man, another is added: just as physicians employ several body medicines when one has no effect. In like manner the Church, when excommunication does not sufficiently restrain certain men, employs the compulsion of the secular arm. If, however, one punishment suffices, another should not be employed.

Summa Th. II-II EN Qu.37