Summa Th. II-II EN Qu.109


We must now consider truth and the vices opposed thereto. Concerning truth there are four points of inquiry:

(1) Whether truth is a virtue?

(2) Whether it is a special virtue?

(3) Whether it is a part of justice?

(4) Whether it inclines to that which is less?

Whether truth is a virtue?

Objection: 1. It seems that truth is not a virtue. For the first of virtues is faith, whose object is truth. Since then the object precedes the habit and the act, it seems that truth is not a virtue, but something prior to virtue.
2. Further, according to the Philosopher (Ethic. iv, 7), it belongs to truth that a man should state things concerning himself to be neither more nor less than they are. But this is not always praiseworthy---neither in good things, since according to Pr 27,2, "Let another praise thee, and not thy own mouth"---nor even in evil things, because it is written in condemnation of certain people (Is 3,9): "They have proclaimed abroad their sin as Sodom, and they have not hid it." Therefore truth is not a virtue.
3. Further, every virtue is either theological, or intellectual, or moral. Now truth is not a theological virtue, because its object is not God but temporal things. For Tully says (De Invent. Rhet. ii) that by "truth we faithfully represent things as they are were, or will be." Likewise it is not one of the intellectual virtues, but their end. Nor again is it a moral virtue, since it is not a mean between excess and deficiency, for the more one tells the truth, the better it is. Therefore truth is not a virtue.

On the contrary The Philosopher both in the Second and in the Fourth Book of Ethics places truth among the other virtues.
I answer that Truth can be taken in two ways. First, for that by reason of which a thing is said to be true, and thus truth is not a virtue, but the object or end of a virtue: because, taken in this way, truth is not a habit, which is the genus containing virtue, but a certain equality between the understanding or sign and the thing understood or signified, or again between a thing and its rule, as stated in the I 16,1 I 21,2. Secondly, truth may stand for that by which a person says what is true, in which sense one is said to be truthful. This truth or truthfulness must needs be a virtue, because to say what is true is a good act: and virtue is "that which makes its possessor good, and renders his action good."

Reply to Objection: 1. This argument takes truth in the first sense.
2. To state that which concerns oneself, in so far as it is a statement of what is true, is good generically. Yet this does not suffice for it to be an act of virtue, since it is requisite for that purpose that it should also be clothed with the due circumstances, and if these be not observed, the act will be sinful. Accordingly it is sinful to praise oneself without due cause even for that which is true: and it is also sinful to publish one's sin, by praising oneself on that account, or in any way proclaiming it uselessly.
3. A person who says what is true, utters certain signs which are in conformity with things; and such signs are either words, or external actions, or any external thing. Now such kinds of things are the subject-matter of the moral virtues alone, for the latter are concerned with the use of the external members, in so far as this use is put into effect at the command of the will. Wherefore truth is neither a theological, nor an intellectual, but a moral virtue. And it is a mean between excess and deficiency in two ways. First, on the part of the object, secondly, on the part of the act. On the part of the object, because the true essentially denotes a kind of equality, and equal is a mean between more and less. Hence for the very reason that a man says what is true about himself, he observes the mean between one that says more than the truth about himself, and one that says less than the truth. On the part of the act, to observe the mean is to tell the truth, when one ought, and as one ought. Excess consists in making known one's own affairs out of season, and deficiency in hiding them when one ought to make them known.

Whether truth is a special virtue?

Objection: 1. It seems that truth is not a special virtue. For the true and the good are convertible. Now goodness is not a special virtue, in fact every virtue is goodness, because "it makes its possessor good." Therefore truth is not a special virtue.
2. Further, to make known what belongs to oneself is an act of truth as we understand it here. But this belongs to every virtue, since every virtuous habit is made known by its own act. Therefore truth is not a special virtue.
3. Further, the truth of life is the truth whereby one lives aright, and of which it is written (Is 38,3): "I beseech Thee . . . remember how I have walked before Thee in truth, and with a perfect heart." Now one lives aright by any virtue, as follows from the definition of virtue given above (I-II 55,4). Therefore truth is not a special virtue.
4. Further, truth seems to be the same as simplicity, since hypocrisy is opposed to both. But simplicity is not a special virtue, since it rectifies the intention, and that is required in every virtue. Therefore neither is truth a special virtue.

On the contrary It is numbered together with other virtues (Ethic. ii, 7).
I answer that The nature of human virtue consists in making a man's deed good. Consequently whenever we find a special aspect of goodness in human acts, it is necessary that man be disposed thereto by a special virtue. And since according to Augustine (De Nat. Boni iii) good consists in order, it follows that a special aspect of good will be found where there is a special order. Now there is a special order whereby our externals, whether words or deeds, are duly ordered in relation to some thing, as sign to thing signified: and thereto man is perfected by the virtue of truth. Wherefore it is evident that truth is a special virtue.

Reply to Objection: 1. The true and the good are convertible as to subject, since every true thing is good, and every good thing is true. But considered logically, they exceed one another, even as the intellect and will exceed one another. For the intellect understands the will and many things besides, and the will desires things pertaining to the intellect, and many others. Wherefore the "true" considered in its proper aspect as a perfection of the intellect is a particular good, since it is something appetible: and in like manner the "good" considered in its proper aspect as the end of the appetite is something true, since it is something intelligible. Therefore since virtue includes the aspect of goodness, it is possible for truth to be a special virtue, just as the "true" is a special good; yet it is not possible for goodness to be a special virtue, since rather, considered logically, it is the genus of virtue.
2. The habits of virtue and vice take their species from what is directly intended, and not from that which is accidental and beside the intention. Now that a man states that which concerns himself, belongs to the virtue of truth, as something directly intended: although it may belong to other virtues consequently and beside his principal intention. For the brave man intends to act bravely: and that he shows his fortitude by acting bravely is a consequence beside his principal intention.
3. The truth of life is the truth whereby a thing is true, not whereby a person says what is true. Life like anything else is said to be true, from the fact that it attains its rule and measure, namely, the divine law; since rectitude of life depends on conformity to that law. This truth or rectitude is common to every virtue.
4. Simplicity is so called from its opposition to duplicity, whereby, to wit, a man shows one thing outwardly while having another in his heart: so that simplicity pertains to this virtue. And it rectifies the intention, not indeed directly (since this belongs to every virtue), but by excluding duplicity, whereby a man pretends one thing and intends another.

Whether truth is a part of justice?

Objection: 1. It seems that truth is not a part of justice. For it seems proper to justice to give another man his due. But, by telling the truth, one does not seem to give another man his due, as is the case in all the foregoing parts of justice. Therefore truth is not a part of justice.
2. Further, truth pertains to the intellect: whereas justice is in the will, as stated above (Question [58], Article [4]). Therefore truth is not a part of justice.
3. Further, according to Jerome truth is threefold, namely, "truth of life," "truth of justice," and "truth of doctrine." But none of these is a part of justice. For truth of life comprises all virtues, as stated above (Article [2], ad 3): truth of justice is the same as justice, so that it is not one of its parts; and truth of doctrine belongs rather to the intellectual virtues. Therefore truth is nowise a part of justice.

On the contrary Tully (De Invent. Rhet. ii) reckons truth among the parts of justice.
I answer that As stated above (Question [80]), a virtue is annexed to justice, as secondary to a principal virtue, through having something in common with justice, while falling short from the perfect virtue thereof. Now the virtue of truth has two things in common with justice. In the first place it is directed to another, since the manifestation, which we have stated to be an act of truth, is directed to another, inasmuch as one person manifests to another the things that concern himself. In the second place, justice sets up a certain equality between things, and this the virtue of truth does also, for it equals signs to the things which concern man himself. Nevertheless it falls short of the proper aspect of justice, as to the notion of debt: for this virtue does not regard legal debt, which justice considers, but rather the moral debt, in so far as, out of equity, one man owes another a manifestation of the truth. Therefore truth is a part of justice, being annexed thereto as a secondary virtue to its principal.

Reply to Objection: 1. Since man is a social animal, one man naturally owes another whatever is necessary for the preservation of human society. Now it would be impossible for men to live together, unless they believed one another, as declaring the truth one to another. Hence the virtue of truth does, in a manner, regard something as being due.
2. Truth, as known, belongs to the intellect. But man, by his own will, whereby he uses both habits and members, utters external signs in order to manifest the truth, and in this way the manifestation of the truth is an act of the will.
3. The truth of which we are speaking now differs from the truth of life, as stated in the preceding Article [2], ad 3.We speak of the truth of justice in two ways. In one way we refer to the fact that justice itself is a certain rectitude regulated according to the rule of the divine law; and in this way the truth of justice differs from the truth of life, because by the truth of life a man lives aright in himself, whereas by the truth of justice a man observes the rectitude of the law in those judgments which refer to another man: and in this sense the truth of justice has nothing to do with the truth of which we speak now, as neither has the truth of life. In another way the truth of justice may be understood as referring to the fact that, out of justice, a man manifests the truth, as for instance when a man confesses the truth, or gives true evidence in a court of justice. This truth is a particular act of justice, and does not pertain directly to this truth of which we are now speaking, because, to wit, in this manifestation of the truth a man's chief intention is to give another man his due. Hence the Philosopher says (Ethic. iv, 7) in describing this virtue: "We are not speaking of one who is truthful in his agreements, nor does this apply to matters in which justice or injustice is questioned."
The truth of doctrine consists in a certain manifestation of truths relating to science wherefore neither does this truth directly pertain to this virtue, but only that truth whereby a man, both in life and in speech, shows himself to be such as he is, and the things that concern him, not other, and neither greater nor less, than they are. Nevertheless since truths of science, as known by us, are something concerning us, and pertain to this virtue, in this sense the truth of doctrine may pertain to this virtue, as well as any other kind of truth whereby a man manifests, by word or deed, what he knows.

Whether the virtue of truth inclines rather to that which is less?

Objection: 1. It seems that the virtue of truth does not incline to that which is less. For as one incurs falsehood by saying more, so does one by saying less: thus it is no more false that four are five, than that four are three. But "every falsehood is in itself evil, and to be avoided," as the Philosopher declares (Ethic. iv, 7). Therefore the virtue of truth does not incline to that which is less rather than to that which is greater.
2. Further, that a virtue inclines to the one extreme rather than to the other, is owing to the fact that the virtue's mean is nearer to the one extreme than to the other: thus fortitude is nearer to daring than to timidity. But the mean of truth is not nearer to one extreme than to the other; because truth, since it is a kind of equality, holds to the exact mean. Therefore truth does not more incline to that which is less.
3. Further, to forsake the truth for that which is less seems to amount to a denial of the truth, since this is to subtract therefrom; and to forsake the truth for that which is greater seems to amount to an addition thereto. Now to deny the truth is more repugnant to truth than to add something to it, because truth is incompatible with the denial of truth, whereas it is compatible with addition. Therefore it seems that truth should incline to that which is greater rather than to that which is less.

On the contrary The Philosopher says (Ethic. iv, 7) that "by this virtue a man declines rather from the truth towards that which is less."
I answer that There are two ways of declining from the truth to that which is less. First, by affirming, as when a man does not show the whole good that is in him, for instance science, holiness and so forth. This is done without prejudice to truth, since the lesser is contained in the greater: and in this way this virtue inclines to what is less. For, as the Philosopher says (Ethic. iv, 7), "this seems to be more prudent because exaggerations give annoyance." For those who represent themselves as being greater than they are, are a source of annoyance to others, since they seem to wish to surpass others: whereas those who make less account of themselves are a source of pleasure, since they seem to defer to others by their moderation. Hence the Apostle says (2Co 12,6): "Though I should have a mind to glory, I shall not be foolish: for I will say the truth. But I forbear, lest any man should think of me above that which he seeth in me or anything he heareth from me."Secondly, one may incline to what is less by denying, so as to say that what is in us is not. In this way it does not belong to this virtue to incline to what is less, because this would imply falsehood. And yet this would be less repugnant to the truth, not indeed as regards the proper aspect of truth, but as regards the aspect of prudence, which should be safeguarded in all the virtues. For since it is fraught with greater danger and is more annoying to others, it is more repugnant to prudence to think or boast that one has what one has not, than to think or say that one has not what one has.

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

VICES OPPOSED TO TRUTH (Questions [110]-114)


We must now consider the vices opposed to truth, and (1) lying: (2) dissimulation or hypocrisy: (3) boasting and the opposite vice. Concerning lying there are four points of inquiry:

(1) Whether lying, as containing falsehood, is always opposed to truth?

(2) Of the species of lying;

(3) Whether lying is always a sin?

(4) Whether it is always a mortal sin?

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.
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.
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 (Question [109], Article [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.
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.
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.

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.
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.
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 Ps 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. In 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. In 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.

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

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.
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" (Ex 1,21). Therefore a lie is not a sin.
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 (Gn 12 Gn 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 (Gn 27,27-29). Again, Judith is commended (Jdt 15,10-11) although she lied to Holofernes. Therefore not every lie is a sin.
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.
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.
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 (Si 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."
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 (Ex 2,21): "And because the midwives feared God, He built them houses." But the subsequent lie was not meritorious.
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 (Questions. Super. Gen. xxvi; Contra Mend. x; Contra Faust. xxii). Wherefore Abraham himself said (Gn 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.
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).
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 (2Co 1), did not lie, because obstacles had arisen which prevented him.
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."

Summa Th. II-II EN Qu.109