Summa Th. II-II EN Qu.10 a.7

Whether one ought to dispute with unbelievers in public?

Objection: 1. It would seem that one ought not to dispute with unbelievers in public. For the Apostle says (2Tm 2,14): "Contend not in words, for it is to no profit, but to the subverting of the hearers." But it is impossible to dispute with unbelievers publicly without contending in words. Therefore one ought not to dispute publicly with unbelievers.
2. Further, the law of Martianus Augustus confirmed by the canons [*De Sum. Trin. Cod. lib. i, leg. Nemo] expresses itself thus: "It is an insult to the judgment of the most religious synod, if anyone ventures to debate or dispute in public about matters which have once been judged and disposed of." Now all matters of faith have been decided by the holy councils. Therefore it is an insult to the councils, and consequently a grave sin to presume to dispute in public about matters of faith.
3. Further, disputations are conducted by means of arguments. But an argument is a reason in settlement of a dubious matter: whereas things that are of faith, being most certain, ought not to be a matter of doubt. Therefore one ought not to dispute in public about matters of faith.

On the contrary It is written (Ac 9,22 Ac 9,29) that "Saul increased much more in strength, and confounded the Jews," and that "he spoke . . . to the gentiles and disputed with the Greeks."
I answer that In disputing about the faith, two things must be observed: one on the part of the disputant; the other on the part of his hearers. On the part of the disputant, we must consider his intention. For if he were to dispute as though he had doubts about the faith, and did not hold the truth of faith for certain, and as though he intended to probe it with arguments, without doubt he would sin, as being doubtful of the faith and an unbeliever. On the other hand, it is praiseworthy to dispute about the faith in order to confute errors, or for practice.On the part of the hearers we must consider whether those who hear the disputation are instructed and firm in the faith, or simple and wavering. As to those who are well instructed and firm in the faith, there can be no danger in disputing about the faith in their presence. But as to simple-minded people, we must make a distinction; because either they are provoked and molested by unbelievers, for instance, Jews or heretics, or pagans who strive to corrupt the faith in them, or else they are not subject to provocation in this matter, as in those countries where there are not unbelievers. In the first case it is necessary to dispute in public about the faith, provided there be those who are equal and adapted to the task of confuting errors; since in this way simple people are strengthened in the faith, and unbelievers are deprived of the opportunity to deceive, while if those who ought to withstand the perverters of the truth of faith were silent, this would tend to strengthen error. Hence Gregory says (Pastor. ii, 4): "Even as a thoughtless speech gives rise to error, so does an indiscreet silence leave those in error who might have been instructed." On the other hand, in the second case it is dangerous to dispute in public about the faith, in the presence of simple people, whose faith for this very reason is more firm, that they have never heard anything differing from what they believe. Hence it is not expedient for them to hear what unbelievers have to say against the faith.

Reply to Objection: 1. The Apostle does not entirely forbid disputations, but such as are inordinate, and consist of contentious words rather than of sound speeches.
2. That law forbade those public disputations about the faith, which arise from doubting the faith, but not those which are for the safeguarding thereof.
3. One ought to dispute about matters of faith, not as though one doubted about them, but in order to make the truth known, and to confute errors. For, in order to confirm the faith, it is necessary sometimes to dispute with unbelievers, sometimes by defending the faith, according to 1P 3,15: "Being ready always to satisfy everyone that asketh you a reason of that hope and faith which is in you [*Vulg.: 'Of that hope which is in you' St. Thomas' reading is apparently taken from Bede]." Sometimes again, it is necessary, in order to convince those who are in error, according to Titus 1:9: "That he may be able to exhort in sound doctrine and to convince the gainsayers."

Whether unbelievers ought to be compelled to the faith?

Objection: 1. It would seem that unbelievers ought by no means to be compelled to the faith. For it is written (Mt 13,28) that the servants of the householder, in whose field cockle had been sown, asked him: "Wilt thou that we go and gather it up?" and that he answered: "No, lest perhaps gathering up the cockle, you root up the wheat also together with it": on which passage Chrysostom says (Hom. xlvi in Matth.): "Our Lord says this so as to forbid the slaying of men. For it is not right to slay heretics, because if you do you will necessarily slay many innocent persons." Therefore it seems that for the same reason unbelievers ought not to be compelled to the faith.
2. Further, we read in the Decretals (Dist. xlv can., De Judaeis): "The holy synod prescribes, with regard to the Jews, that for the future, none are to be compelled to believe." Therefore, in like manner, neither should unbelievers be compelled to the faith.
3. Further, Augustine says (Tract. xxvi in Joan.) that "it is possible for a man to do other things against his will, but he cannot believe unless he is willing." Therefore it seems that unbelievers ought not to be compelled to the faith.
4. It is said in God's person (Ez 18,32 [*Ez 33,11]): "I desire not the death of the sinner [Vulg.: 'of him that dieth']." Now we ought to conform our will to the Divine will, as stated above (I-II 19,9 I-II 19,10). Therefore we should not even wish unbelievers to be put to death.

On the contrary It is written (Lc 14,23): "Go out into the highways and hedges; and compel them to come in." Now men enter into the house of God, i.e. into Holy Church, by faith. Therefore some ought to be compelled to the faith.On the other hand, there are unbelievers who at some time have accepted the faith, and professed it, such as heretics and all apostates: such should be submitted even to bodily compulsion, that they may fulfil what they have promised, and hold what they, at one time, received.

Reply to Objection: 1. Some have understood the authority quoted to forbid, not the excommunication but the slaying of heretics, as appears from the words of Chrysostom. Augustine too, says (Ep ad Vincent. xciii) of himself: "It was once my opinion that none should be compelled to union with Christ, that we should deal in words, and fight with arguments. However this opinion of mine is undone, not by words of contradiction, but by convincing examples. Because fear of the law was so profitable, that many say: Thanks be to the Lord Who has broken our chains asunder." Accordingly the meaning of Our Lord's words, "Suffer both to grow until the harvest," must be gathered from those which precede, "lest perhaps gathering up the cockle, you root the wheat also together with it." For, Augustine says (Contra Ep. Parmen. iii, 2) "these words show that when this is not to be feared, that is to say, when a man's crime is so publicly known, and so hateful to all, that he has no defenders, or none such as might cause a schism, the severity of discipline should not slacken."
2. Those Jews who have in no way received the faith, ought not by no means to be compelled to the faith: if, however, they have received it, they ought to be compelled to keep it, as is stated in the same chapter.
3. Just as taking a vow is a matter of will, and keeping a vow, a matter of obligation, so acceptance of the faith is a matter of the will, whereas keeping the faith, when once one has received it, is a matter of obligation. Wherefore heretics should be compelled to keep the faith. Thus Augustine says to the Count Boniface (Ep. clxxxv): "What do these people mean by crying out continually: 'We may believe or not believe just as we choose. Whom did Christ compel?' They should remember that Christ at first compelled Paul and afterwards taught Him."
4. As Augustine says in the same letter, "none of us wishes any heretic to perish. But the house of David did not deserve to have peace, unless his son Absalom had been killed in the war which he had raised against his father. Thus if the Catholic Church gathers together some of the perdition of others, she heals the sorrow of her maternal heart by the delivery of so many nations."

Whether it is lawful to communicate with unbelievers?

Objection: 1. It would seem that it is lawful to communicate with unbelievers. For the Apostle says (1Co 10,27): "If any of them that believe not, invite you, and you be willing to go, eat of anything that is set before you." And Chrysostom says (Hom. xxv super Epist. ad He): "If you wish to go to dine with pagans, we permit it without any reservation." Now to sit at table with anyone is to communicate with him. Therefore it is lawful to communicate with unbelievers.
2. Further, the Apostle says (1Co 5,12): "What have I to do to judge them that are without?" Now unbelievers are without. When, therefore, the Church forbids the faithful to communicate with certain people, it seems that they ought not to be forbidden to communicate with unbelievers.
3. Further, a master cannot employ his servant, unless he communicate with him, at least by word, since the master moves his servant by command. Now Christians can have unbelievers, either Jews, or pagans, or Saracens, for servants. Therefore they can lawfully communicate with them.

On the contrary It is written (Dt 7,2-3): "Thou shalt make no league with them, nor show mercy to them; neither shalt thou make marriages with them": and a gloss on Lv 15,19, "The woman who at the return of the month," etc. says: "It is so necessary to shun idolatry, that we should not come in touch with idolaters or their disciples, nor have any dealings with them."
I answer that Communication with a particular person is forbidden to the faithful, in two ways: first, as a punishment of the person with whom they are forbidden to communicate; secondly, for the safety of those who are forbidden to communicate with others. Both motives can be gathered from the Apostle's words (1Co 5,6). For after he had pronounced sentence of excommunication, he adds as his reason: "Know you not that a little leaven corrupts the whole lump?" and afterwards he adds the reason on the part of the punishment inflicted by the sentence of the Church when he says (1Co 5,12): "Do not you judge them that are within?"Accordingly, in the first way the Church does not forbid the faithful to communicate with unbelievers, who have not in any way received the Christian faith, viz. with pagans and Jews, because she has not the right to exercise spiritual judgment over them, but only temporal judgment, in the case when, while dwelling among Christians they are guilty of some misdemeanor, and are condemned by the faithful to some temporal punishment. On the other hand, in this way, i.e. as a punishment, the Church forbids the faithful to communicate with those unbelievers who have forsaken the faith they once received, either by corrupting the faith, as heretics, or by entirely renouncing the faith, as apostates, because the Church pronounces sentence of excommunication on both.With regard to the second way, it seems that one ought to distinguish according to the various conditions of persons, circumstances and time. For some are firm in the faith; and so it is to be hoped that their communicating with unbelievers will lead to the conversion of the latter rather than to the aversion of the faithful from the faith. These are not to be forbidden to communicate with unbelievers who have not received the faith, such as pagans or Jews, especially if there be some urgent necessity for so doing. But in the case of simple people and those who are weak in the faith, whose perversion is to be feared as a probable result, they should be forbidden to communicate with unbelievers, and especially to be on very familiar terms with them, or to communicate with them without necessity.

Reply to Objection: 1. This suffices for the Reply to the First Objection.
2. The Church does not exercise judgment against unbelievers in the point of inflicting spiritual punishment on them: but she does exercise judgment over some of them in the matter of temporal punishment. It is under this head that sometimes the Church, for certain special sins, withdraws the faithful from communication with certain unbelievers.
3. There is more probability that a servant who is ruled by his master's commands, will be converted to the faith of his master who is a believer, than if the case were the reverse: and so the faithful are not forbidden to have unbelieving servants. If, however, the master were in danger, through communicating with such a servant, he should send him away, according to Our Lord's command (Mt 18,8): "If . . . thy foot scandalize thee, cut it off, and cast it from thee."With regard to the argument in the contrary [*The Leonine Edition gives this solution before the Reply OBJ 2] sense the reply is that the Lord gave this command in reference to those nations into whose territory the Jews were about to enter. For the latter were inclined to idolatry, so that it was to be feared lest, through frequent dealings with those nations, they should be estranged from the faith: hence the text goes on (Dt 7,4): "For she will turn away thy son from following Me."

Whether unbelievers may have authority or dominion over the faithful?

Objection: 1. It would seem that unbelievers may have authority or dominion over the faithful. For the Apostle says (1Tm 6,1): "Whosoever are servants under the yoke, let them count their masters worthy of all honor": and it is clear that he is speaking of unbelievers, since he adds (1Tm 6,2): "But they that have believing masters, let them not despise them." Moreover it is written (1P 2,18): "Servants be subject to your masters with all fear, not only to the good and gentle, but also to the froward." Now this command would not be contained in the apostolic teaching unless unbelievers could have authority over the faithful. Therefore it seems that unbelievers can have authority over the faithful.
2. Further, all the members of a prince's household are his subjects. Now some of the faithful were members of unbelieving princes' households, for we read in the Epistle to the Philippians (4:22): "All the saints salute you, especially they that are of Caesar's household," referring to Nero, who was an unbeliever. Therefore unbelievers can have authority over the faithful.
3. Further, according to the Philosopher (Polit. i, 2) a slave is his master's instrument in matters concerning everyday life, even as a craftsman's laborer is his instrument in matters concerning the working of his art. Now, in such matters, a believer can be subject to an unbeliever, for he may work on an unbeliever's farm. Therefore unbelievers may have authority over the faithful even as to dominion.

On the contrary Those who are in authority can pronounce judgment on those over whom they are placed. But unbelievers cannot pronounce judgment on the faithful, for the Apostle says (1Co 6,1): "Dare any of you, having a matter against another, go to be judged before the unjust," i.e. unbelievers, "and not before the saints?" Therefore it seems that unbelievers cannot have authority over the faithful.
I answer that That this question may be considered in two ways. First, we may speak of dominion or authority of unbelievers over the faithful as of a thing to be established for the first time. This ought by no means to be allowed, since it would provoke scandal and endanger the faith, for subjects are easily influenced by their superiors to comply with their commands, unless the subjects are of great virtue: moreover unbelievers hold the faith in contempt, if they see the faithful fall away. Hence the Apostle forbade the faithful to go to law before an unbelieving judge. And so the Church altogether forbids unbelievers to acquire dominion over believers, or to have authority over them in any capacity whatever.Secondly, we may speak of dominion or authority, as already in force: and here we must observe that dominion and authority are institutions of human law, while the distinction between faithful and unbelievers arises from the Divine law. Now the Divine law which is the law of grace, does not do away with human law which is the law of natural reason. Wherefore the distinction between faithful and unbelievers, considered in itself, does not do away with dominion and authority of unbelievers over the faithful.Nevertheless this right of dominion or authority can be justly done away with by the sentence or ordination of the Church who has the authority of God: since unbelievers in virtue of their unbelief deserve to forfeit their power over the faithful who are converted into children of God.This the Church does sometimes, and sometimes not. For among those unbelievers who are subject, even in temporal matters, to the Church and her members, the Church made the law that if the slave of a Jew became a Christian, he should forthwith receive his freedom, without paying any price, if he should be a "vernaculus," i.e. born in slavery; and likewise if, when yet an unbeliever, he had been bought for his service: if, however, he had been bought for sale, then he should be offered for sale within three months. Nor does the Church harm them in this, because since those Jews themselves are subject to the Church, she can dispose of their possessions, even as secular princes have enacted many laws to be observed by their subjects, in favor of liberty. On the other hand, the Church has not applied the above law to those unbelievers who are not subject to her or her members, in temporal matters, although she has the right to do so: and this, in order to avoid scandal, for as Our Lord showed (Mt 17,25-26) that He could be excused from paying the tribute, because "the children are free," yet He ordered the tribute to be paid in order to avoid giving scandal. Thus Paul too, after saying that servants should honor their masters, adds, "lest the name of the Lord and His doctrine be blasphemed."

Reply to Objection: 1. This suffices for the Reply to the First Objection.
2. The authority of Caesar preceded the distinction of faithful from unbelievers. Hence it was not cancelled by the conversion of some to the faith. Moreover it was a good thing that there should be a few of the faithful in the emperor's household, that they might defend the rest of the faithful. Thus the Blessed Sebastian encouraged those whom he saw faltering under torture, and, the while, remained hidden under the military cloak in the palace of Diocletian.
3. Slaves are subject to their masters for their whole lifetime, and are subject to their overseers in everything: whereas the craftsman's laborer is subject to him for certain special works. Hence it would be more dangerous for unbelievers to have dominion or authority over the faithful, than that they should be allowed to employ them in some craft. Wherefore the Church permits Christians to work on the land of Jews, because this does not entail their living together with them. Thus Solomon besought the King of Tyre to send master workmen to hew the trees, as related in 1R 5,6. Yet, if there be reason to fear that the faithful will be perverted by such communications and dealings, they should be absolutely forbidden.

Whether the rites of unbelievers ought to be tolerated?

Objection: 1. It would seem that rites of unbelievers ought not to be tolerated. For it is evident that unbelievers sin in observing their rites: and not to prevent a sin, when one can, seems to imply consent therein, as a gloss observes on Rm 1,32: "Not only they that do them, but they also that consent to them that do them." Therefore it is a sin to tolerate their rites.
2. Further, the rites of the Jews are compared to idolatry, because a gloss on Ga 5,1, "Be not held again under the yoke of bondage," says: "The bondage of that law was not lighter than that of idolatry." But it would not be allowable for anyone to observe the rites of idolatry, in fact Christian princes at first caused the temples of idols to be closed, and afterwards, to be destroyed, as Augustine relates (De Civ. Dei xviii, 54). Therefore it follows that even the rites of Jews ought not to be tolerated.
3. Further, unbelief is the greatest of sins, as stated above (Article [3]). Now other sins such as adultery, theft and the like, are not tolerated, but are punishable by law. Therefore neither ought the rites of unbelievers to be tolerated.

On the contrary Gregory [*Regist. xi, Ep. 15: cf. Decret., dist. xlv, can., Qui sincera] says, speaking of the Jews: "They should be allowed to observe all their feasts, just as hitherto they and their fathers have for ages observed them."
I answer that Human government is derived from the Divine government, and should imitate it. Now although God is all-powerful and supremely good, nevertheless He allows certain evils to take place in the universe, which He might prevent, lest, without them, greater goods might be forfeited, or greater evils ensue. Accordingly in human government also, those who are in authority, rightly tolerate certain evils, lest certain goods be lost, or certain greater evils be incurred: thus Augustine says (De Ordine ii, 4): "If you do away with harlots, the world will be convulsed with lust." Hence, though unbelievers sin in their rites, they may be tolerated, either on account of some good that ensues therefrom, or because of some evil avoided. Thus from the fact that the Jews observe their rites, which, of old, foreshadowed the truth of the faith which we hold, there follows this good---that our very enemies bear witness to our faith, and that our faith is represented in a figure, so to speak. For this reason they are tolerated in the observance of their rites.On the other hand, the rites of other unbelievers, which are neither truthful nor profitable are by no means to be tolerated, except perchance in order to avoid an evil, e.g. the scandal or disturbance that might ensue, or some hindrance to the salvation of those who if they were unmolested might gradually be converted to the faith. For this reason the Church, at times, has tolerated the rites even of heretics and pagans, when unbelievers were very numerous.

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

Whether the children of Jews and other unbelievers ought to be baptized against their parents' will?

Objection: 1. It would seem that the children of Jews and of other unbelievers ought to be baptized against their parents' will. For the bond of marriage is stronger than the right of parental authority over children, since the right of parental authority can be made to cease, when a son is set at liberty; whereas the marriage bond cannot be severed by man, according to Mt 19,6: "What . . . God hath joined together let no man put asunder." And yet the marriage bond is broken on account of unbelief: for the Apostle says (1Co 7,15): "If the unbeliever depart, let him depart. For a brother or sister is not under servitude in such cases": and a canon [*Can. Uxor legitima, and Idololatria, qu. i] says that "if the unbelieving partner is unwilling to abide with the other, without insult to their Creator, then the other partner is not bound to cohabitation." Much more, therefore, does unbelief abrogate the right of unbelieving parents' authority over their children: and consequently their children may be baptized against their parents' will.
2. Further, one is more bound to succor a man who is in danger of everlasting death, than one who is in danger of temporal death. Now it would be a sin, if one saw a man in danger of temporal death and failed to go to his aid. Since, then, the children of Jews and other unbelievers are in danger of everlasting death, should they be left to their parents who would imbue them with their unbelief, it seems that they ought to be taken away from them and baptized, and instructed in the faith.
3. Further, the children of a bondsman are themselves bondsmen, and under the power of his master. Now the Jews are bondsmen of kings and princes: therefore their children are also. Consequently kings and princes have the power to do what they will with Jewish children. Therefore no injustice is committed if they baptize them against their parents' wishes.
4. Further, every man belongs more to God, from Whom he has his soul, than to his carnal father, from whom he has his body. Therefore it is not unjust if Jewish children be taken away from their parents, and consecrated to God in Baptism.
5. Further, Baptism avails for salvation more than preaching does, since Baptism removes forthwith the stain of sin and the debt of punishment, and opens the gate of heaven. Now if danger ensue through not preaching, it is imputed to him who omitted to preach, according to the words of Ez 33,6 about the man who "sees the sword coming and sounds not the trumpet." Much more therefore, if Jewish children are lost through not being baptized are they accounted guilty of sin, who could have baptized them and did not.

On the contrary Injustice should be done to no man. Now it would be an injustice to Jews if their children were to be baptized against their will, since they would lose the rights of parental authority over their children as soon as these were Christians. Therefore these should not be baptized against their parents' will.
I answer that The custom of the Church has very great authority and ought to be jealously observed in all things, since the very doctrine of catholic doctors derives its authority from the Church. Hence we ought to abide by the authority of the Church rather than by that of an Augustine or a Jerome or of any doctor whatever. Now it was never the custom of the Church to baptize the children of the Jews against the will of their parents, although at times past there have been many very powerful catholic princes like Constantine and Theodosius, with whom most holy bishops have been on most friendly terms, as Sylvester with Constantine, and Ambrose with Theodosius, who would certainly not have failed to obtain this favor from them if it had been at all reasonable. It seems therefore hazardous to repeat this assertion, that the children of Jews should be baptized against their parents' wishes, in contradiction to the Church's custom observed hitherto.There are two reasons for this custom. One is on account of the danger to the faith. For children baptized before coming to the use of reason, afterwards when they come to perfect age, might easily be persuaded by their parents to renounce what they had unknowingly embraced; and this would be detrimental to the faith.The other reason is that it is against natural justice. For a child is by nature part of its father: thus, at first, it is not distinct from its parents as to its body, so long as it is enfolded within its mother's womb; and later on after birth, and before it has the use of its free-will, it is enfolded in the care of its parents, which is like a spiritual womb, for so long as man has not the use of reason, he differs not from an irrational animal; so that even as an ox or a horse belongs to someone who, according to the civil law, can use them when he likes, as his own instrument, so, according to the natural law, a son, before coming to the use of reason, is under his father's care. Hence it would be contrary to natural justice, if a child, before coming to the use of reason, were to be taken away from its parents' custody, or anything done to it against its parents' wish. As soon, however, as it begins to have the use of its free-will, it begins to belong to itself, and is able to look after itself, in matters concerning the Divine or the natural law, and then it should be induced, not by compulsion but by persuasion, to embrace the faith: it can then consent to the faith, and be baptized, even against its parents' wish; but not before it comes to the use of reason. Hence it is said of the children of the fathers of old that they were saved in the faith of their parents; whereby we are given to understand that it is the parents' duty to look after the salvation of their children, especially before they come to the use of reason.

Reply to Objection: 1. In the marriage bond, both husband and wife have the use of the free-will, and each can assent to the faith without the other's consent. But this does not apply to a child before it comes to the use of reason: yet the comparison holds good after the child has come to the use of reason, if it is willing to be converted.
2. No one should be snatched from natural death against the order of civil law: for instance, if a man were condemned by the judge to temporal death, nobody ought to rescue him by violence: hence no one ought to break the order of the natural law, whereby a child is in the custody of its father, in order to rescue it from the danger of everlasting death.
3. Jews are bondsmen of princes by civil bondage, which does not exclude the order of natural or Divine law.
4. Man is directed to God by his reason, whereby he can know Him. Hence a child before coming to the use of reason, in the natural order of things, is directed to God by its parents' reason, under whose care it lies by nature: and it is for them to dispose of the child in all matters relating to God.
5. The peril that ensues from the omission of preaching, threatens only those who are entrusted with the duty of preaching. Hence it had already been said (Ez 3,17): "I have made thee a watchman to the children [Vulg.: 'house'] of Israel." On the other hand, to provide the sacraments of salvation for the children of unbelievers is the duty of their parents. Hence it is they whom the danger threatens, if through being deprived of the sacraments their children fail to obtain salvation.


We must now consider heresy: under which head there are four points of inquiry:

(1) Whether heresy is a kind of unbelief?

(2) Of the matter about which it is;

(3) Whether heretics should be tolerated?

(4) Whether converts should be received?

Whether heresy is a species of unbelief?

Objection: 1. It would seem that heresy is not a species of unbelief. For unbelief is in the understanding, as stated above (Question [10], Article [2]). Now heresy would seem not to pertain to the understanding, but rather to the appetitive power; for Jerome says on Ga 5,19: [*Cf. Decretals xxiv, qu. iii, cap. 27] "The works of the flesh are manifest: Heresy is derived from a Greek word meaning choice, whereby a man makes choice of that school which he deems best." But choice is an act of the appetitive power, as stated above (I-II 13,1). Therefore heresy is not a species of unbelief.
2. Further, vice takes its species chiefly from its end; hence the Philosopher says (Ethic. v, 2) that "he who commits adultery that he may steal, is a thief rather than an adulterer." Now the end of heresy is temporal profit, especially lordship and glory, which belong to the vice of pride or covetousness: for Augustine says (De Util. Credendi i) that "a heretic is one who either devises or follows false and new opinions, for the sake of some temporal profit, especially that he may lord and be honored above others." Therefore heresy is a species of pride rather than of unbelief.
3. Further, since unbelief is in the understanding, it would seem not to pertain to the flesh. Now heresy belongs to the works of the flesh, for the Apostle says (Ga 5,19): "The works of the flesh are manifest, which are fornication, uncleanness," and among the others, he adds, "dissensions, sects," which are the same as heresies. Therefore heresy is not a species of unbelief.

On the contrary Falsehood is contrary to truth. Now a heretic is one who devises or follows false or new opinions. Therefore heresy is opposed to the truth, on which faith is founded; and consequently it is a species of unbelief.
I answer that The word heresy as stated in the first objection denotes a choosing. Now choice as stated above (I-II 13,3) is about things directed to the end, the end being presupposed. Now, in matters of faith, the will assents to some truth, as to its proper good, as was shown above (Question [4], Article [3]): wherefore that which is the chief truth, has the character of last end, while those which are secondary truths, have the character of being directed to the end.Now, whoever believes, assents to someone's words; so that, in every form of unbelief, the person to whose words assent is given seems to hold the chief place and to be the end as it were; while the things by holding which one assents to that person hold a secondary place. Consequently he that holds the Christian faith aright, assents, by his will, to Christ, in those things which truly belong to His doctrine.Accordingly there are two ways in which a man may deviate from the rectitude of the Christian faith. First, because he is unwilling to assent to Christ: and such a man has an evil will, so to say, in respect of the very end. This belongs to the species of unbelief in pagans and Jews. Secondly, because, though he intends to assent to Christ, yet he fails in his choice of those things wherein he assents to Christ, because he chooses not what Christ really taught, but the suggestions of his own mind.Therefore heresy is a species of unbelief, belonging to those who profess the Christian faith, but corrupt its dogmas.

Reply to Objection: 1. Choice regards unbelief in the same way as the will regards faith, as stated above.
2. Vices take their species from their proximate end, while, from their remote end, they take their genus and cause. Thus in the case of adultery committed for the sake of theft, there is the species of adultery taken from its proper end and object; but the ultimate end shows that the act of adultery is both the result of the theft, and is included under it, as an effect under its cause, or a species under its genus, as appears from what we have said about acts in general (I-II 18,7). Wherefore, as to the case in point also, the proximate end of heresy is adherence to one's own false opinion, and from this it derives its species, while its remote end reveals its cause, viz. that it arises from pride or covetousness.
3. Just as heresy is so called from its being a choosing [*From the Greek (airein) [hairein], to cut off], so does sect derive its name from its being a cutting off [secando], as Isidore states (Etym. viii, 3). Wherefore heresy and sect are the same thing, and each belongs to the works of the flesh, not indeed by reason of the act itself of unbelief in respect of its proximate object, but by reason of its cause, which is either the desire of an undue end in which way it arises from pride or covetousness, as stated in the second objection, or some illusion of the imagination (which gives rise to error, as the Philosopher states in Metaph. iv; Ed. Did. iii, 5), for this faculty has a certain connection with the flesh, in as much as its act is independent on a bodily organ.

Summa Th. II-II EN Qu.10 a.7