Summa Th. II-II EN Qu.72 a.2

Whether reviling or railing is a mortal sin?

Objection: 1. It would seem that reviling or railing is not a mortal sin. For no mortal sin is an act of virtue. Now railing is the act of a virtue, viz. of wittiness (eutrapelia) [*Cf. FS, Question [60], Article [5]] to which it pertains to rail well, according to the Philosopher (Ethic. iv, 8). Therefore railing or reviling is not a mortal sin.
2. Further, mortal sin is not to be found in perfect men; and yet these sometimes give utterance to railing or reviling. Thus the Apostle says (Ga 3,1): "O senseless Galatians!," and our Lord said (Lc 24,25): "O foolish and slow of heart to believe!" Therefore railing or reviling is not a mortal sin.
3. Further, although that which is a venial sin by reason of its genus may become mortal, that which is mortal by reason of its genus cannot become venial, as stated above (FS, Question [88], Articles [4],6). Hence if by reason of its genus it were a mortal sin to give utterance to railing or reviling, it would follow that it is always a mortal sin. But this is apparently untrue, as may be seen in the case of one who utters a reviling word indeliberately or through slight anger. Therefore reviling or railing is not a mortal sin, by reason of its genus.

On the contrary Nothing but mortal sin deserves the eternal punishment of hell. Now railing or reviling deserves the punishment of hell, according to Mt 5,22, "Whosoever shall say to his brother . . . Thou fool, shall be in danger of hell fire." Therefore railing or reviling is a mortal sin.
I answer that As stated above (Article [1]), words are injurious to other persons, not as sounds, but as signs, and this signification depends on the speaker's inward intention. Hence, in sins of word, it seems that we ought to consider with what intention the words are uttered. Since then railing or reviling essentially denotes a dishonoring, if the intention of the utterer is to dishonor the other man, this is properly and essentially to give utterance to railing or reviling: and this is a mortal sin no less than theft or robbery, since a man loves his honor no less than his possessions. If, on the other hand, a man says to another a railing or reviling word, yet with the intention, not of dishonoring him, but rather perhaps of correcting him or with some like purpose, he utters a railing or reviling not formally and essentially, but accidentally and materially, in so far to wit as he says that which might be a railing or reviling. Hence this may be sometimes a venial sin, and sometimes without any sin at all. Nevertheless there is need of discretion in such matters, and one should use such words with moderation, because the railing might be so grave that being uttered inconsiderately it might dishonor the person against whom it is uttered. In such a case a man might commit a mortal sin, even though he did not intend to dishonor the other man: just as were a man incautiously to injure grievously another by striking him in fun, he would not be without blame.

Reply to Objection: 1. It belongs to wittiness to utter some slight mockery, not with intent to dishonor or pain the person who is the object of the mockery, but rather with intent to please and amuse: and this may be without sin, if the due circumstances be observed. on the other hand if a man does not shrink from inflicting pain on the object of his witty mockery, so long as he makes others laugh, this is sinful, as stated in the passage quoted.
2. Just as it is lawful to strike a person, or damnify him in his belongings for the purpose of correction, so too, for the purpose of correction, may one say a mocking word to a person whom one has to correct. It is thus that our Lord called the disciples "foolish," and the Apostle called the Galatians "senseless." Yet, as Augustine says (De Serm. Dom. in Monte ii, 19), "seldom and only when it is very necessary should we have recourse to invectives, and then so as to urge God's service, not our own."
3. Since the sin of railing or reviling depends on the intention of the utterer, it may happen to be a venial sin, if it be a slight railing that does not inflict much dishonor on a man, and be uttered through lightness of heart or some slight anger, without the fixed purpose of dishonoring him, for instance when one intends by such a word to give but little pain.

Whether one ought to suffer oneself to be reviled?

Objection: 1. It would seem that one ought not to suffer oneself to be reviled. For he that suffers himself to be reviled, encourages the reviler. But one ought not to do this. Therefore one ought not to suffer oneself to be reviled, but rather reply to the reviler.
2. Further, one ought to love oneself more than another. Now one ought not to suffer another to be reviled, wherefore it is written (Pr 26,10): "He that putteth a fool to silence appeaseth anger." Therefore neither should one suffer oneself to be reviled.
3. Further, a man is not allowed to revenge himself, for it is said: "Vengeance belongeth to Me, I will repay" [*He 10,30]. Now by submitting to be reviled a man revenges himself, according to Chrysostom (Hom. xxii, in Ep ad Rom.): "If thou wilt be revenged, be silent; thou hast dealt him a fatal blow." Therefore one ought not by silence to submit to reviling words, but rather answer back.

On the contrary It is written (Ps 37,13): "They that sought evils to me spoke vain things," and afterwards (Ps 37,14) he says: "But I as a deaf man, heard not; and as a dumb man not opening his mouth."
I answer that Just as we need patience in things done against us, so do we need it in those said against us. Now the precepts of patience in those things done against us refer to the preparedness of the mind, according to Augustine's (De Serm. Dom. in Monte i, 19) exposition on our Lord's precept, "If one strike thee on thy right cheek, turn to him also the other" [*The words as quoted by St. Thomas are a blending of Mt 5,39 and Lc 6,29]: that is to say, a man ought to be prepared to do so if necessary. But he is not always bound to do this actually: since not even did our Lord do so, for when He received a blow, He said: "Why strikest thou Me?" (Jn 18,23). Consequently the same applies to the reviling words that are said against us. For we are bound to hold our minds prepared to submit to be reviled, if it should be expedient. Nevertheless it sometimes behooves us to withstand against being reviled, and this chiefly for two reasons. First, for the good of the reviler; namely, that his daring may be checked, and that he may not repeat the attempt, according to Pr 26,5, "Answer a fool according to his folly, lest he imagine himself to be wise." Secondly, for the good of many who would be prevented from progressing in virtue on account of our being reviled. Hence Gregory says (Hom. ix, Super Ezech.): "Those who are so placed that their life should be an example to others, ought, if possible, to silence their detractors, lest their preaching be not heard by those who could have heard it, and they continue their evil conduct through contempt of a good life."

Reply to Objection: 1. The daring of the railing reviler should be checked with moderation, i.e. as a duty of charity, and not through lust for one's own honor. Hence it is written (Pr 26,4): "Answer not a fool according to his folly, lest thou be like him."
2. When one man prevents another from being reviled there is not the danger of lust for one's own honor as there is when a man defends himself from being reviled: indeed rather would it seem to proceed from a sense of charity.
3. It would be an act of revenge to keep silence with the intention of provoking the reviler to anger, but it would be praiseworthy to be silent, in order to give place to anger. Hence it is written (Si 8,4): "Strive not with a man that is full of tongue, and heap not wood upon his fire."

Whether reviling arises from anger?

Objection: 1. It would seem that reviling does not arise from anger. For it is written (Pr 11,2): "Where pride is, there shall also be reviling [Douay: 'reproach']." But anger is a vice distinct from pride. Therefore reviling does not arise from anger.
2. Further, it is written (Pr 20,3): "All fools are meddling with revilings [Douay: 'reproaches']." Now folly is a vice opposed to wisdom, as stated above (Question [46], Article [1]); whereas anger is opposed to meekness. Therefore reviling does not arise from anger.
3. Further, no sin is diminished by its cause. But the sin of reviling is diminished if one gives vent to it through anger: for it is a more grievous sin to revile out of hatred than out of anger. Therefore reviling does not arise from anger.

On the contrary Gregory says (Moral. xxxi, 45) that "anger gives rise to revilings."
I answer that While one sin may arise from various causes, it is nevertheless said to have its source chiefly in that one from which it is wont to arise most frequently, through being closely connected with its end. Now reviling is closely connected with anger's end, which is revenge: since the easiest way for the angry man to take revenge on another is to revile him. Therefore reviling arises chiefly from anger.

Reply to Objection: 1. Reviling is not directed to the end of pride which is excellency. Hence reviling does not arise directly from pride. Nevertheless pride disposes a man to revile, in so far as those who think themselves to excel, are more prone to despise others and inflict injuries on them, because they are more easily angered, through deeming it an affront to themselves whenever anything is done against their will.
2. According to the Philosopher (Ethic. vii, 6) "anger listens imperfectly to reason": wherefore an angry man suffers a defect of reason, and in this he is like the foolish man. Hence reviling arises from folly on account of the latter's kinship with anger.
3. According to the Philosopher (Rhet. ii, 4) "an angry man seeks an open offense, but he who hates does not worry about this." Hence reviling which denotes a manifest injury belongs to anger rather than to hatred.


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

(1) What is backbiting?

(2) Whether it is a mortal sin?

(3) Of its comparison with other sins;

(4) Whether it is a sin to listen to backbiting?

Whether backbiting is suitably defined as the blackening of another's character by secret words?

Objection: 1. It would seem that backbiting is not as defined by some [*Albert the Great, Sum. Theol. II, cxvii.], "the blackening of another's good name by words uttered in secret." For "secretly" and "openly" are circumstances that do not constitute the species of a sin, because it is accidental to a sin that it be known by many or by few. Now that which does not constitute the species of a sin, does not belong to its essence, and should not be included in its definition. Therefore it does not belong to the essence of backbiting that it should be done by secret words.
2. Further, the notion of a good name implies something known to the public. If, therefore, a person's good name is blackened by backbiting, this cannot be done by secret words, but by words uttered openly.
3. Further, to detract is to subtract, or to diminish something already existing. But sometimes a man's good name is blackened, even without subtracting from the truth: for instance, when one reveals the crimes which a man has in truth committed. Therefore not every blackening of a good name is backbiting.

On the contrary It is written (Qo 10,11): "If a serpent bite in silence, he is nothing better that backbiteth."
I answer that Just as one man injures another by deed in two ways---openly, as by robbery or by doing him any kind of violence---and secretly, as by theft, or by a crafty blow, so again one man injures another by words in two ways---in one way, openly, and this is done by reviling him, as stated above (Question [72], Article [1])---and in another way secretly, and this is done by backbiting. Now from the fact that one man openly utters words against another man, he would appear to think little of him, so that for this reason he dishonors him, so that reviling is detrimental to the honor of the person reviled. On the other hand, he that speaks against another secretly, seems to respect rather than slight him, so that he injures directly, not his honor but his good name, in so far as by uttering such words secretly, he, for his own part, causes his hearers to have a bad opinion of the person against whom he speaks. For the backbiter apparently intends and aims at being believed. It is therefore evident that backbiting differs from reviling in two points: first, in the way in which the words are uttered, the reviler speaking openly against someone, and the backbiter secretly; secondly, as to the end in view, i.e. as regards the injury inflicted, the reviler injuring a man's honor, the backbiter injuring his good name.

Reply to Objection: 1. In involuntary commutations, to which are reduced all injuries inflicted on our neighbor, whether by word or by deed, the kind of sin is differentiated by the circumstances "secretly" and "openly," because involuntariness itself is diversified by violence and by ignorance, as stated above (Question [65], Article [4]; FS, Question [6], Articles [5],8).
2. The words of a backbiter are said to be secret, not altogether, but in relation to the person of whom they are said, because they are uttered in his absence and without his knowledge. On the other hand, the reviler speaks against a man to his face. Wherefore if a man speaks ill of another in the presence of several, it is a case of backbiting if he be absent, but of reviling if he alone be present: although if a man speak ill of an absent person to one man alone, he destroys his good name not altogether but partly.
3. A man is said to backbite [detrehere] another, not because he detracts from the truth, but because he lessens his good name. This is done sometimes directly, sometimes indirectly. Directly, in four ways: first, by saying that which is false about him; secondly, by stating his sin to be greater than it is; thirdly, by revealing something unknown about him; fourthly, by ascribing his good deeds to a bad intention. Indirectly, this is done either by gainsaying his good, or by maliciously concealing it, or by diminishing it.

Whether backbiting is a mortal sin?

Objection: 1. It would seem that backbiting is not a mortal sin. For no act of virtue is a mortal sin. Now, to reveal an unknown sin, which pertains to backbiting, as stated above (Article [1], ad 3), is an act of the virtue of charity, whereby a man denounces his brother's sin in order that he may amend: or else it is an act of justice, whereby a man accuses his brother. Therefore backbiting is not a mortal sin.
2. Further, a gloss on Pr 24,21, "Have nothing to do with detractors," says: "The whole human race is in peril from this vice." But no mortal sin is to be found in the whole of mankind, since many refrain from mortal sin: whereas they are venial sins that are found in all. Therefore backbiting is a venial sin.
3. Further, Augustine in a homily On the Fire of Purgatory [*Serm. civ in the appendix to St. Augustine's work] reckons it a slight sin "to speak ill without hesitation or forethought." But this pertains to backbiting. Therefore backbiting is a venial sin.

On the contrary It is written (Rm 1,30): "Backbiters, hateful to God," which epithet, according to a gloss, is inserted, "lest it be deemed a slight sin because it consists in words."
I answer that As stated above (Question [72], Article [2]), sins of word should be judged chiefly from the intention of the speaker. Now backbiting by its very nature aims at blackening a man's good name. Wherefore, properly speaking, to backbite is to speak ill of an absent person in order to blacken his good name. Now it is a very grave matter to blacken a man's good name, because of all temporal things a man's good name seems the most precious, since for lack of it he is hindered from doing many things well. For this reason it is written (Si 41,15): "Take care of a good name, for this shall continue with thee, more than a thousand treasures precious and great." Therefore backbiting, properly speaking, is a mortal sin. Nevertheless it happens sometimes that a man utters words, whereby someone's good name is tarnished, and yet he does not intend this, but something else. This is not backbiting strictly and formally speaking, but only materially and accidentally as it were. And if such defamatory words be uttered for the sake of some necessary good, and with attention to the due circumstances, it is not a sin and cannot be called backbiting. But if they be uttered out of lightness of heart or for some unnecessary motive, it is not a mortal sin, unless perchance the spoken word be of such a grave nature, as to cause a notable injury to a man's good name, especially in matters pertaining to his moral character, because from the very nature of the words this would be a mortal sin. And one is bound to restore a man his good name, no less than any other thing one has taken from him, in the manner stated above (Question [62], Article [2]) when we were treating of restitution.

Reply to Objection: 1. As stated above, it is not backbiting to reveal a man's hidden sin in order that he may mend, whether one denounce it, or accuse him for the good of public justice.
2. This gloss does not assert that backbiting is to be found throughout the whole of mankind, but "almost," both because "the number of fools is infinite," [*Qo 1,15] and few are they that walk in the way of salvation, [*Cf. Mt 7,14] and because there are few or none at all who do not at times speak from lightness of heart, so as to injure someone's good name at least slightly, for it is written (Jc 3,2): "If any man offend not in word, the same is a perfect man."
3. Augustine is referring to the case when a man utters a slight evil about someone, not intending to injure him, but through lightness of heart or a slip of the tongue.

Whether backbiting is the gravest of all sins committed against one's neighbor?

Objection: 1. It would seem that backbiting is the gravest of all sins committed against one's neighbor. Because a gloss on Ps 108,4, "Instead of making me a return of love they detracted me," a gloss says: "Those who detract Christ in His members and slay the souls of future believers are more guilty than those who killed the flesh that was soon to rise again." From this it seems to follow that backbiting is by so much a graver sin than murder, as it is a graver matter to kill the soul than to kill the body. Now murder is the gravest of the other sins that are committed against one's neighbor. Therefore backbiting is absolutely the gravest of all.
2. Further, backbiting is apparently a graver sin than reviling, because a man can withstand reviling, but not a secret backbiting. Now backbiting is seemingly a graver sin than adultery, because adultery unites two persons in one flesh, whereas reviling severs utterly those who were united. Therefore backbiting is more grievous than adultery: and yet of all other sins a man commits against his neighbor, adultery is most grave.
3. Further, reviling arises from anger, while backbiting arises from envy, according to Gregory (Moral. xxxi, 45). But envy is a graver sin than anger. Therefore backbiting is a graver sin than reviling; and so the same conclusion follows as before.
4. Further, the gravity of a sin is measured by the gravity of the defect that it causes. Now backbiting causes a most grievous defect, viz. blindness of mind. For Gregory says (Regist. xi, Ep 2): "What else do backbiters but blow on the dust and stir up the dirt into their eyes, so that the more they breathe of detraction, the less they see of the truth?" Therefore backbiting is the most grievous sin committed against one's neighbor.

On the contrary It is more grievous to sin by deed than by word. But backbiting is a sin of word, while adultery, murder, and theft are sins of deed. Therefore backbiting is not graver than the other sins committed against one's neighbor.
I answer that The essential gravity of sins committed against one's neighbor must be weighed by the injury they inflict on him, since it is thence that they derive their sinful nature. Now the greater the good taken away, the greater the injury. And while man's good is threefold, namely the good of his soul, the good of his body, and the good of external things; the good of the soul, which is the greatest of all, cannot be taken from him by another save as an occasional cause, for instance by an evil persuasion, which does not induce necessity. On the other hand the two latter goods, viz. of the body and of external things, can be taken away by violence. Since, however, the goods of the body excel the goods of external things, those sins which injure a man's body are more grievous than those which injure his external things. Consequently, among other sins committed against one's neighbor, murder is the most grievous, since it deprives man of the life which he already possesses: after this comes adultery, which is contrary to the right order of human generation, whereby man enters upon life. In the last place come external goods, among which a man's good name takes precedence of wealth because it is more akin to spiritual goods, wherefore it is written (Pr 22,1): "A good name is better than great riches." Therefore backbiting according to its genus is a more grievous sin than theft, but is less grievous than murder or adultery. Nevertheless the order may differ by reason of aggravating or extenuating circumstances.The accidental gravity of a sin is to be considered in relation to the sinner, who sins more grievously, if he sins deliberately than if he sins through weakness or carelessness. In this respect sins of word have a certain levity, in so far as they are apt to occur through a slip of the tongue, and without much forethought.

Reply to Objection: 1. Those who detract Christ by hindering the faith of His members, disparage His Godhead, which is the foundation of our faith. Wherefore this is not simple backbiting but blasphemy.
2. Reviling is a more grievous sin than backbiting, in as much as it implies greater contempt of one's neighbor: even as robbery is a graver sin than theft, as stated above (Question [66], Article [9]). Yet reviling is not a more grievous sin than adultery. For the gravity of adultery is measured, not from its being a union of bodies, but from being a disorder in human generation. Moreover the reviler is not the sufficient cause of unfriendliness in another man, but is only the occasional cause of division among those who were united, in so far, to wit, as by declaring the evils of another, he for his own part severs that man from the friendship of other men, though they are not forced by his words to do so. Accordingly a backbiter is a murderer "occasionally," since by his words he gives another man an occasion for hating or despising his neighbor. For this reason it is stated in the Epistle of Clement [*Ad Jacob. Ep. i], that "backbiters are murderers," i.e. occasionally; because "he that hateth his brother is a murderer" (1Jn 3,15).
3. Anger seeks openly to be avenged, as the Philosopher states (Rhet. ii, 2): wherefore backbiting which takes place in secret, is not the daughter of anger, as reviling is, but rather of envy, which strives by any means to lessen one's neighbor's glory. Nor does it follow from this that backbiting is more grievous than reviling: since a lesser vice can give rise to a greater sin, just as anger gives birth to murder and blasphemy. For the origin of a sin depends on its inclination to an end, i.e. on the thing to which the sin turns, whereas the gravity of a sin depends on what it turns away from.
4. Since "a man rejoiceth in the sentence of his mouth" (Pr 15,23), it follows that a backbiter more and more loves and believes what he says, and consequently more and more hates his neighbor, and thus his knowledge of the truth becomes less and less. This effect however may also result from other sins pertaining to hate of one's neighbor.

Whether it is a grave sin for the listener to suffer the backbiter?

Objection: 1. It would seem that the listener who suffers a backbiter does not sin grievously. For a man is not under greater obligations to others than to himself. But it is praiseworthy for a man to suffer his own backbiters: for Gregory says (Hom. ix, super Ezech): "Just as we ought not to incite the tongue of backbiters, lest they perish, so ought we to suffer them with equanimity when they have been incited by their own wickedness, in order that our merit may be the greater." Therefore a man does not sin if he does not withstand those who backbite others.
2. Further, it is written (Si 4,30): "In no wise speak against the truth." Now sometimes a person tells the truth while backbiting, as stated above (Article [1], ad 3). Therefore it seems that one is not always bound to withstand a backbiter.
3. Further, no man should hinder what is profitable to others. Now backbiting is often profitable to those who are backbitten: for Pope Pius [*St. Pius I] says [*Append. Grat. ad can. Oves, caus. vi, qu. 1]: "Not unfrequently backbiting is directed against good persons, with the result that those who have been unduly exalted through the flattery of their kindred, or the favor of others, are humbled by backbiting." Therefore one ought not to withstand backbiters.

On the contrary Jerome says (Ep ad Nepot. lii): "Take care not to have an itching tongue, nor tingling ears, that is, neither detract others nor listen to backbiters."
I answer that According to the Apostle (Rm 1,32), they "are worthy of death . . . not only they that" commit sins, "but they also that consent to them that do them." Now this happens in two ways. First, directly, when, to wit, one man induces another to sin, or when the sin is pleasing to him: secondly, indirectly, that is, if he does not withstand him when he might do so, and this happens sometimes, not because the sin is pleasing to him, but on account of some human fear.Accordingly we must say that if a man list ens to backbiting without resisting it, he seems to consent to the backbiter, so that he becomes a participator in his sin. And if he induces him to backbite, or at least if the detraction be pleasing to him on account of his hatred of the person detracted, he sins no less than the detractor, and sometimes more. Wherefore Bernard says (De Consid. ii, 13): "It is difficult to say which is the more to be condemned the backbiter or he that listens to backbiting." If however the sin is not pleasing to him, and he fails to withstand the backbiter, through fear negligence, or even shame, he sins indeed, but much less than the backbiter, and, as a rule venially. Sometimes too this may be a mortal sin, either because it is his official duty to cor. rect the backbiter, or by reason of some consequent danger; or on account of the radical reason for which human fear may sometimes be a mortal sin, as stated above (Question [19], Article [3]).

Reply to Objection: 1. No man hears himself backbitten, because when a man is spoken evil of in his hearing, it is not backbiting, properly speaking, but reviling, as stated above (Article [1], ad 2). Yet it is possible for the detractions uttered against a person to come to his knowledge through others telling him, and then it is left to his discretion whether he will suffer their detriment to his good name, unless this endanger the good of others, as stated above (Question [72], Article [3]). Wherefore his patience may deserve commendation for as much as he suffers patiently being detracted himself. But it is not left to his discretion to permit an injury to be done to another's good name, hence he is accounted guilty if he fails to resist when he can, for the same reason whereby a man is bound to raise another man's ass lying "underneath his burden," as commanded in Dt 21,4 [*Ex 23,5].
2. One ought not always to withstand a backbiter by endeavoring to convince him of falsehood, especially if one knows that he is speaking the truth: rather ought one to reprove him with words, for that he sins in backbiting his brother, or at least by our pained demeanor show him that we are displeased with his backbiting, because according to Pr 25,23, "the north wind driveth away rain, as doth a sad countenance a backbiting tongue."
3. The profit one derives from being backbitten is due, not to the intention of the backbiter, but to the ordinance of God Who produces good out of every evil. Hence we should none the less withstand backbiters, just as those who rob or oppress others, even though the oppressed and the robbed may gain merit by patience.

Q74: OF TALE-BEARING [*'Susurratio,' i.e. whispering] (TWO ARTICLES)

We must now consider tale-bearing: under which head there are two points of inquiry:

(1) Whether tale-bearing is a sin distinct from backbiting?

(2) Which of the two is the more grievous?

Whether tale-bearing is a sin distinct from backbiting?

Objection: 1. It would seem that tale-bearing is not a distinct sin from backbiting. Isidore says (Etym. x): "The susurro [tale-bearer] takes his name from the sound of his speech, for he speaks disparagingly not to the face but into the ear." But to speak of another disparagingly belongs to backbiting. Therefore tale-bearing is not a distinct sin from backbiting.
2. Further, it is written (Lv 19,16): "Thou shalt not be an informer [Douay: 'a detractor'] nor a tale-bearer [Douay: 'whisperer'] among the people." But an informer is apparently the same as a backbiter. Therefore neither does tale-bearing differ from backbiting.
3. Further, it is written (Si 28,15): "The tale-bearer [Douay: 'whisperer'] and the double-tongued is accursed." But a double-tongued man is apparently the same as a backbiter, because a backbiter speaks with a double tongue, with one in your absence, with another in your presence. Therefore a tale-bearer is the same as a backbiter.

On the contrary A gloss on Rm 1,29-30, "Tale-bearers, backbiters [Douay: 'whisperers, detractors']" says: "Tale-bearers sow discord among friends; backbiters deny or disparage others' good points."
I answer that The tale-bearer and the backbiter agree in matter, and also in form or mode of speaking, since they both speak evil secretly of their neighbor: and for this reason these terms are sometimes used one for the other. Hence a gloss on Si 5,16, "Be not called a tale-bearer [Douay: 'whisperer']" says: "i.e. a backbiter." They differ however in end, because the backbiter intends to blacken his neighbor's good name, wherefore he brings forward those evils especially about his neighbor which are likely to defame him, or at least to depreciate his good name: whereas a tale-bearer intends to sever friendship, as appears from the gloss quoted above and from the saying of Pr 26,20, "Where the tale-bearer is taken away, contentions shall cease." Hence it is that a tale-bearer speaks such ill about his neighbors as may stir his hearer's mind against them, according to Si 28,11, "A sinful man will trouble his friends, and bring in debate in the midst of them that are at peace."

Reply to Objection: 1. A tale-bearer is called a backbiter in so far as he speaks ill of another; yet he differs from a backbiter since he intends not to speak ill as such, but to say anything that may stir one man against another, though it be good simply, and yet has a semblance of evil through being unpleasant to the hearer.
2. An informer differs from a tale-bearer and a backbiter, for an informer is one who charges others publicly with crimes, either by accusing or by railing them, which does not apply to a backbiter or tale-bearer.
3. A double-tongued person is properly speaking a tale-bearer. For since friendship is between two, the tale-bearer strives to sever friendship on both sides. Hence he employs a double tongue towards two persons, by speaking ill of one to the other: wherefore it is written (Si 28,15): "The tale-bearer [Douay: 'whisperer'] and the double-tongued is accursed," and then it is added, "for he hath troubled many that were peace."

Summa Th. II-II EN Qu.72 a.2