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Home > Summa Theologiae > Second Part of the Second Part > Question 110

Question 110. The vices opposed to truth, and first of lying

  1. Is lying, as containing falsehood, always opposed to truth?
  2. The species of lying
  3. Is lying always a sin?
  4. Is it always a mortal sin?

Article 1. Whether lying is always opposed to truth?

Objection 1. It seems that lying is not always opposed to truth. For opposites are incompatible with one another. But lying is compatible with truth, since that speaks the truth, thinking it to be false, lies, according to Augustine (Lib. De Mendac. iii). Therefore lying is not opposed to truth.

Objection 2. Further, the virtue of truth applies not only to words but also to deeds, since according to the Philosopher (Ethic. iv, 7) by this virtue one tells the truth both in one's speech and in one's life. But lying applies only to words, for Augustine says (Contra Mend. xii) that "a lie is a false signification by words." Accordingly, it seems that lying is not directly opposed to the virtue of truth.

Objection 3. Further, Augustine says (Lib. De Mendac. iii) that the "liar's sin is the desire to deceive." But this is not opposed to truth, but rather to benevolence or justice. Therefore lying is not opposed to truth.

On the contrary, Augustine says (Contra Mend. x): "Let no one doubt that it is a lie to tell a falsehood in order to deceive. Wherefore a false statement uttered with intent to deceive is a manifest lie." But this is opposed to truth. Therefore lying is opposed to truth.

I answer that, A moral act takes its species from two things, its object, and its end: for the end is the object of the will, which is the first mover in moral acts. And the power moved by the will has its own object, which is the proximate object of the voluntary act, and stands in relation to the will's act towards the end, as material to formal, as stated above (I-II:18:6; I-II:18:7).

Now it has been said above (II-II:109:1 ad 3) that the virtue of truth—and consequently the opposite vices—regards a manifestation made by certain signs: and this manifestation or statement is an act of reason comparing sign with the thing signified; because every representation consists in comparison, which is the proper act of the reason. Wherefore though dumb animals manifest something, yet they do not intend to manifest anything: but they do something by natural instinct, and a manifestation is the result. But when this manifestation or statement is a moral act, it must needs be voluntary, and dependent on the intention of the will. Now the proper object of a manifestation or statement is the true or the false. And the intention of a bad will may bear on two things: one of which is that a falsehood may be told; while the other is the proper effect of a false statement, namely, that someone may be deceived.

Accordingly if these three things concur, namely, falsehood of what is said, the will to tell a falsehood, and finally the intention to deceive, then there is falsehood—materially, since what is said is false, formally, on account of the will to tell an untruth, and effectively, on account of the will to impart a falsehood.

However, the essential notion of a lie is taken from formal falsehood, from the fact namely, that a person intends to say what is false; wherefore also the word "mendacium" [lie] is derived from its being in opposition to the "mind." Consequently if one says what is false, thinking it to be true, it is false materially, but not formally, because the falseness is beside the intention of the speaker so that it is not a perfect lie, since what is beside the speaker's intention is accidental for which reason it cannot be a specific difference. If, on the other hand, one utters' falsehood formally, through having the will to deceive, even if what one says be true, yet inasmuch as this is a voluntary and moral act, it contains falseness essentially and truth accidentally, and attains the specific nature of a lie.

That a person intends to cause another to have a false opinion, by deceiving him, does not belong to the species of lying, but to perfection thereof, even as in the physical order, a thing acquires its species if it has its form, even though the form's effect be lacking; for instance a heavy body which is held up aloft by force, lest it come down in accordance with the exigency of its form. Therefore it is evident that lying is directly an formally opposed to the virtue of truth.

Reply to Objection 1. We judge of a thing according to what is in it formally and essentially rather than according to what is in it materially and accidentally. Hence it is more in opposition to truth, considered as a moral virtue, to tell the truth with the intention of telling a falsehood than to tell a falsehood with the intention of telling the truth.

Reply to Objection 2. As Augustine says (De Doctr. Christ. ii), words hold the chief place among other signs. And so when it is said that "a lie is a false signification by words," the term "words" denotes every kind of sign. Wherefore if a person intended to signify something false by means of signs, he would not be excused from lying.

Reply to Objection 3. The desire to deceive belongs to the perfection of lying, but not to its species, as neither does any effect belong to the species of its cause.

Article 2. Whether lies are sufficiently divided into officious, jocose, and mischievous lies?

Objection 1. It seems that lies are not sufficiently divided into "officious," "jocose" and "mischievous" lies. For a division should be made according to that which pertains to a thing by reason of its nature, as the Philosopher states (Metaph. vii, text. 43; De Part. Animal i, 3). But seemingly the intention of the effect resulting from a moral act is something beside and accidental to the species of that act, so that an indefinite number of effects can result from one act. Now this division is made according to the intention of the effect: for a "jocose" lie is told in order to make fun, an "officious" lie for some useful purpose, and a "mischievous" lie in order to injure someone. Therefore lies are unfittingly divided in this way.

Objection 2. Further, Augustine (Contra Mendac. xiv) gives eight kinds of lies. The first is "in religious doctrine"; the second is "a lie that profits no one and injures someone"; the third "profits one party so as to injure another"; the fourth is "told out of mere lust of lying and deceiving"; the fifth is "told out of the desire to please"; the sixth "injures no one, and profits someone in saving his money"; the seventh "injures no one and profits someone in saving him from death"; the eighth "injures no one, and profits someone in saving him from defilement of the body." Therefore it seems that the first division of lies is insufficient.

Objection 3. Further, the Philosopher (Ethic. iv, 7) divides lying into "boasting," which exceeds the truth in speech, and "irony," which falls short of the truth by saying something less: and these two are not contained under any one of the kinds mentioned above. Therefore it seems that the aforesaid division of lies is inadequate.

On the contrary, A gloss on Psalm 5:7, "Thou wilt destroy all that speak a lie," says "that there are three kinds of lies; for some are told for the wellbeing and convenience of someone; and there is another kind of lie that is told in fun; but the third kind of lie is told out of malice." The first of these is called an officious lie, the second a jocose lie, the third a mischievous lie. Therefore lies are divided into these three kinds.

I answer that, Lies may be divided in three ways. First, with respect to their nature as lies: and this is the proper and essential division of lying. On this way, according to the Philosopher (Ethic. iv, 7), lies are of two kinds, namely, the lie which goes beyond the truth, and this belongs to "boasting," and the lie which stops short of the truth, and this belongs to "irony." This division is an essential division of lying itself, because lying as such is opposed to truth, as stated in the preceding Article: and truth is a kind of equality, to which more and less are in essential opposition.

Secondly, lies may be divided with respect to their nature as sins, and with regard to those things that aggravate or diminish the sin of lying, on the part of the end intended. Now the sin of lying is aggravated, if by lying a person intends to injure another, and this is called a "mischievous" lie, while the sin of lying is diminished if it be directed to some good—either of pleasure and then it is a "jocose" lie, or of usefulness, and then we have the "officious" lie, whereby it is intended to help another person, or to save him from being injured. On this way lies are divided into the three kinds aforesaid.

Thirdly, lies are divided in a more general way, with respect to their relation to some end, whether or not this increase or diminish their gravity: and in this way the division comprises eight kinds, as stated in the Second Objection. Here the first three kinds are contained under "mischievous" lies, which are either against God, and then we have the lie "in religious doctrine," or against man, and this either with the sole intention of injuring him, and then it is the second kind of lie, which "profits no one, and injures someone"; or with the intention of injuring one and at the same time profiting another, and this is the third kind of lie, "which profits one, and injures another." Of these the first is the most grievous, because sins against God are always more grievous, as stated above (I-II:73:3): and the second is more grievous than the third, since the latter's gravity is diminished by the intention of profiting another.

After these three, which aggravate the sin of lying, we have a fourth, which has its own measure of gravity without addition or diminution; and this is the lie which is told "out of mere lust of lying and deceiving." This proceeds from a habit, wherefore the Philosopher says (Ethic. iv, 7) that "the liar, when he lies from habit, delights in lying."

The four kinds that follow lessen the gravity of the sin of lying. For the fifth kind is the jocose lie, which is told "with a desire to please": and the remaining three are comprised under the officious lie, wherein something useful to another person is intended. This usefulness regards either external things, and then we have the sixth kind of lie, which "profits someone in saving his money"; or his body, and this is the seventh kind, which "saves a man from death"; or the morality of his virtue, and this is the eighth kind, which "saves him from unlawful defilement of his body."

Now it is evident that the greater the good intended, the more is the sin of lying diminished in gravity. Wherefore a careful consideration of the matter will show that these various kinds of lies are enumerated in their order of gravity: since the useful good is better than the pleasurable good, and life of the body than money, and virtue than the life of the body.

This suffices for the Replies to the Objections.

Article 3. Whether every lie is a sin?

Objection 1. It seems that not every lie is a sin. For it is evident that the evangelists did not sin in the writing of the Gospel. Yet they seem to have told something false: since their accounts of the words of Christ and of others often differ from one another: wherefore seemingly one of them must have given an untrue account. Therefore not every lie is a sin.

Objection 2. Further, no one is rewarded by God for sin. But the midwives of Egypt were rewarded by God for a lie, for it is stated that "God built them houses" (Exodus 1:21). Therefore a lie is not a sin.

Objection 3. Further, the deeds of holy men are related in Sacred Writ that they may be a model of human life. But we read of certain very holy men that they lied. Thus (Genesis 12 and 20) we are told that Abraham said of his wife that she was his sister. Jacob also lied when he said that he was Esau, and yet he received a blessing (Genesis 27:27-29). Again, Judith is commended (Judith 15:10-11) although she lied to Holofernes. Therefore not every lie is a sin.

Objection 4. Further, one ought to choose the lesser evil in order to avoid the greater: even so a physician cuts off a limb, lest the whole body perish. Yet less harm is done by raising a false opinion in a person's mind, than by someone slaying or being slain. Therefore a man may lawfully lie, to save another from committing murder, or another from being killed.

Objection 5. Further, it is a lie not to fulfill what one has promised. Yet one is not bound to keep all one's promises: for Isidore says (Synonym. ii): "Break your faith when you have promised ill." Therefore not every lie is a sin.

Objection 6. Further, apparently a lie is a sin because thereby we deceive our neighbor: wherefore Augustine says (Lib. De Mend. xxi): "Whoever thinks that there is any kind of lie that is not a sin deceives himself shamefully, since he deems himself an honest man when he deceives others." Yet not every lie is a cause of deception, since no one is deceived by a jocose lie; seeing that lies of this kind are told, not with the intention of being believed, but merely for the sake of giving pleasure. Hence again we find hyperbolical expressions in Holy Writ. Therefore not every lie is a sin.

On the contrary, It is written (Sirach 7:14): "Be not willing to make any manner of lie."

I answer that, An action that is naturally evil in respect of its genus can by no means be good and lawful, since in order for an action to be good it must be right in every respect: because good results from a complete cause, while evil results from any single defect, as Dionysius asserts (Div. Nom. iv). Now a lie is evil in respect of its genus, since it is an action bearing on undue matter. For as words are naturally signs of intellectual acts, it is unnatural and undue for anyone to signify by words something that is not in his mind. Hence the Philosopher says (Ethic. iv, 7) that "lying is in itself evil and to be shunned, while truthfulness is good and worthy of praise." Therefore every lie is a sin, as also Augustine declares (Contra Mend. i).

Reply to Objection 1. It is unlawful to hold that any false assertion is contained either in the Gospel or in any canonical Scripture, or that the writers thereof have told untruths, because faith would be deprived of its certitude which is based on the authority of Holy Writ. That the words of certain people are variously reported in the Gospel and other sacred writings does not constitute a lie. Hence Augustine says (De Consens. Evang. ii): "He that has the wit to understand that in order to know the truth it is necessary to get at the sense, will conclude that he must not be the least troubled, no matter by what words that sense is expressed." Hence it is evident, as he adds (De Consens. Evang. ii), that "we must not judge that someone is lying, if several persons fail to describe in the same way and in the same words a thing which they remember to have seen or heard."

Reply to Objection 2. The midwives were rewarded, not for their lie, but for their fear of God, and for their good-will, which latter led them to tell a lie. Hence it is expressly stated (Exodus 2:21): "And because the midwives feared God, He built them houses." But the subsequent lie was not meritorious.

Reply to Objection 3. In Holy Writ, as Augustine observes (Lib. De Mend. v), the deeds of certain persons are related as examples of perfect virtue: and we must not believe that such persons were liars. If, however, any of their statements appear to be untruthful, we must understand such statements to have been figurative and prophetic. Hence Augustine says (Lib. De Mend. v): "We must believe that whatever is related of those who, in prophetical times, are mentioned as being worthy of credit, was done and said by them prophetically." As to Abraham "when he said that Sara was his sister, he wished to hide the truth, not to tell a lie, for she is called his sister since she was the daughter of his father," Augustine says (QQ. Super. Gen. xxvi; Contra Mend. x; Contra Faust. xxii). Wherefore Abraham himself said (Genesis 20:12): "She is truly my sister, the daughter of my father, and not the daughter of my mother," being related to him on his father's side. Jacob's assertion that he was Esau, Isaac's first-born, was spoken in a mystical sense, because, to wit, the latter's birthright was due to him by right: and he made use of this mode of speech being moved by the spirit of prophecy, in order to signify a mystery, namely, that the younger people, i.e. the Gentiles, should supplant the first-born, i.e. the Jews.

Some, however, are commended in the Scriptures, not on account of perfect virtue, but for a certain virtuous disposition, seeing that it was owing to some praiseworthy sentiment that they were moved to do certain undue things. It is thus that Judith is praised, not for lying to Holofernes, but for her desire to save the people, to which end she exposed herself to danger. And yet one might also say that her words contain truth in some mystical sense.

Reply to Objection 4. A lie is sinful not only because it injures one's neighbor, but also on account of its inordinateness, as stated above in this Article. Now it is not allowed to make use of anything inordinate in order to ward off injury or defects from another: as neither is it lawful to steal in order to give an alms, except perhaps in a case of necessity when all things are common. Therefore it is not lawful to tell a lie in order to deliver another from any danger whatever. Nevertheless it is lawful to hide the truth prudently, by keeping it back, as Augustine says (Contra Mend. x).

Reply to Objection 5. A man does not lie, so long as he has a mind to do what he promises, because he does not speak contrary to what he has in mind: but if he does not keep his promise, he seems to act without faith in changing his mind. He may, however, be excused for two reasons. First, if he has promised something evidently unlawful, because he sinned in promise, and did well to change his mind. Secondly, if circumstances have changed with regard to persons and the business in hand. For, as Seneca states (De Benef. iv), for a man to be bound to keep a promise, it is necessary for everything to remain unchanged: otherwise neither did he lie in promising—since he promised what he had in his mind, due circumstances being taken for granted—nor was he faithless in not keeping his promise, because circumstances are no longer the same. Hence the Apostle, though he did not go to Corinth, whither he had promised to go (2 Corinthians 1), did not lie, because obstacles had arisen which prevented him.

Reply to Objection 6. An action may be considered in two ways. First, in itself, secondly, with regard to the agent. Accordingly a jocose lie, from the very genus of the action, is of a nature to deceive; although in the intention of the speaker it is not told to deceive, nor does it deceive by the way it is told. Nor is there any similarity in the hyperbolical or any kind of figurative expressions, with which we meet in Holy Writ: because, as Augustine says (Lib. De Mend. v), "it is not a lie to do or say a thing figuratively: because every statement must be referred to the thing stated: and when a thing is done or said figuratively, it states what those to whom it is tendered understand it to signify."

Article 4. Whether every lie is a mortal sin?

Objection 1. It seems that every lie is a mortal sin. For it is written (Psalm 6:7): "Thou wilt destroy all that speak a lie," and (Wisdom 1:11): "The mouth that belieth killeth the soul." Now mortal sin alone causes destruction and death of the soul. Therefore every lie is a mortal sin.

Objection 2. Further, whatever is against a precept of the decalogue is a mortal sin. Now lying is against this precept of the decalogue: "Thou shalt not bear false witness." Therefore every lie is a mortal sin.

Objection 3. Further, Augustine says (De Doctr. Christ. i, 36): "Every liar breaks his faith in lying, since forsooth he wishes the person to whom he lies to have faith in him, and yet he does not keep faith with him, when he lies to him: and whoever breaks his faith is guilty of iniquity." Now no one is said to break his faith or "to be guilty of iniquity," for a venial sin. Therefore no lie is a venial sin.

Objection 4. Further, the eternal reward is not lost save for a mortal sin. Now, for a lie the eternal reward was lost, being exchanged for a temporal meed. For Gregory says (Moral. xviii) that "we learn from the reward of the midwives what the sin of lying deserves: since the reward which they deserved for their kindness, and which they might have received in eternal life, dwindled into a temporal meed on account of the lie of which they were guilty." Therefore even an officious lie, such as was that of the midwives, which seemingly is the least of lies, is a mortal sin.

Objection 5. Further, Augustine says (Lib. De Mend. xvii) that "it is a precept of perfection, not only not to lie at all, but not even to wish to lie." Now it is a mortal sin to act against a precept. Therefore every lie of the perfect is a mortal sin: and consequently so also is a lie told by anyone else, otherwise the perfect would be worse off than others.

On the contrary, Augustine says on Psalm 5:7, "Thou wilt destroy," etc.: "There are two kinds of lie, that are not grievously sinful yet are not devoid of sin, when we lie either in joking, or for the sake of our neighbor's good." But every mortal sin is grievous. Therefore jocose and officious lies are not mortal sins.

I answer that, A mortal sin is, properly speaking, one that is contrary to charity whereby the soul lives in union with God, as stated above (II-II:24:12; II-II:35:3). Now a lie may be contrary to charity in three ways: first, in itself; secondly, in respect of the evil intended; thirdly, accidentally.

A lie may be in itself contrary to charity by reason of its false signification. For if this be about divine things, it is contrary to the charity of God, whose truth one hides or corrupts by such a lie; so that a lie of this kind is opposed not only to the virtue of charity, but also to the virtues of faith and religion: wherefore it is a most grievous and a mortal sin. If, however, the false signification be about something the knowledge of which affects a man's good, for instance if it pertain to the perfection of science or to moral conduct, a lie of this description inflicts an injury on one's neighbor, since it causes him to have a false opinion, wherefore it is contrary to charity, as regards the love of our neighbor, and consequently is a mortal sin. On the other hand, if the false opinion engendered by the lie be about some matter the knowledge of which is of no consequence, then the lie in question does no harm to one's neighbor; for instance, if a person be deceived as to some contingent particulars that do not concern him. Wherefore a lie of this kind, considered in itself, is not a mortal sin.

As regards the end in view, a lie may be contrary to charity, through being told with the purpose of injuring God, and this is always a mortal sin, for it is opposed to religion; or in order to injure one's neighbor, in his person, his possessions or his good name, and this also is a mortal sin, since it is a mortal sin to injure one's neighbor, and one sins mortally if one has merely the intention of committing a mortal sin. But if the end intended be not contrary to charity, neither will the lie, considered under this aspect, be a mortal sin, as in the case of a jocose lie, where some little pleasure is intended, or in an officious lie, where the good also of one's neighbor is intended. Accidentally a lie may be contrary to charity by reason of scandal or any other injury resulting therefrom: and thus again it will be a mortal sin, for instance if a man were not deterred through scandal from lying publicly.

Reply to Objection 1. The passages quoted refer to the mischievous lie, as a gloss explains the words of Psalm 5:7, "Thou wilt destroy all that speak a lie."

Reply to Objection 2. Since all the precepts of the decalogue are directed to the love of God and our neighbor, as stated above (II-II:44:1 ad 3; I-II:100:5 ad 1), a lie is contrary to a precept of the decalogue, in so far as it is contrary to the love of God and our neighbor. Hence it is expressly forbidden to bear false witness against our neighbor.

Reply to Objection 3. Even a venial sin can be called "iniquity" in a broad sense, in so far as it is beside the equity of justice; wherefore it is written (1 John 3:4): "Every sin is iniquity [Vulgate: 'And sin is iniquity.']." It is in this sense that Augustine is speaking.

Reply to Objection 4. The lie of the midwives may be considered in two ways. First as regards their feeling of kindliness towards the Jews, and their reverence and fear of God, for which their virtuous disposition is commended. For this an eternal reward is due. Wherefore Jerome (in his exposition of Isaiah 65:21, 'And they shall build houses') explains that God "built them spiritual houses." Secondly, it may be considered with regard to the external act of lying. For thereby they could merit, not indeed eternal reward, but perhaps some temporal meed, the deserving of which was not inconsistent with the deformity of their lie, though this was inconsistent with their meriting an eternal reward. It is in this sense that we must understand the words of Gregory, and not that they merited by that lie to lose the eternal reward as though they had already merited it by their preceding kindliness, as the objection understands the words to mean.

Reply to Objection 5. Some say that for the perfect every lie is a mortal sin. But this assertion is unreasonable. For no circumstance causes a sin to be infinitely more grievous unless it transfers it to another species. Now a circumstance of person does not transfer a sin to another species, except perhaps by reason of something annexed to that person, for instance if it be against his vow: and this cannot apply to an officious or jocose lie. Wherefore an officious or a jocose lie is not a mortal sin in perfect men, except perhaps accidentally on account of scandal. We may take in this sense the saying of Augustine that "it is a precept of perfection not only not to lie at all, but not even to wish to lie": although Augustine says this not positively but dubiously, for he begins by saying: "Unless perhaps it is a precept," etc. Nor does it matter that they are placed in a position to safeguard the truth: because they are bound to safeguard the truth by virtue of their office in judging or teaching, and if they lie in these matters their lie will be a mortal sin: but it does not follow that they sin mortally when they lie in other matters.

The Summa Theologiæ of St. Thomas Aquinas
Second and Revised Edition, 1920
Literally translated by Fathers of the English Dominican Province
Online Edition Copyright © 2017 by Kevin Knight
Nihil Obstat. F. Innocentius Apap, O.P., S.T.M., Censor. Theol.
Imprimatur. Edus. Canonicus Surmont, Vicarius Generalis. Westmonasterii.
Nihil Obstat. F. Raphael Moss, O.P., S.T.L. and F. Leo Moore, O.P., S.T.L.
Imprimatur. F. Beda Jarrett, O.P., S.T.L., A.M., Prior Provincialis Angliæ


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