Summa Th. II-II EN Qu.110 a.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.
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 (FS, Question [73], Article [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."

Whether every lie is a mortal sin?

Objection: 1. It seems that every lie is a mortal sin. For it is written (Ps 6,7): "Thou wilt destroy all that speak a lie," and (Sg 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.
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.
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.
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.
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 Ps 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 (Question [24], Article [12]; Question [35], Article [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 Ps 5,7, "Thou wilt destroy all that speak a lie."
2. Since all the precepts of the decalogue are directed to the love of God and our neighbor, as stated above (Question [44], Article [1], ad 3; FS, Question [100], Article [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.
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 (1Jn 3,4): "Every sin is iniquity [*Vulg.: 'And sin is iniquity.']." It is in this sense that Augustine is speaking.
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 Is 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.
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.


In due sequence we must consider dissimulation and hypocrisy. Under this head there are four points of inquiry:

(1) Whether all dissimulation is a sin?

(2) Whether hypocrisy is dissimulation?

(3) Whether it is opposed to truth?

(4) Whether it is a mortal sin?

Whether all dissimulation is a sin?

Objection: 1. It seems that not all dissimulation is a sin. For it is written (Lc 24,28) that our Lord "pretended [Douay: 'made as though'] he would go farther"; and Ambrose in his book on the Patriarchs (De Abraham i) says of Abraham that he "spoke craftily to his servants, when he said" (Gn 22,5): "I and the boy will go with speed as far as yonder, and after we have worshipped, will return to you." Now to pretend and to speak craftily savor of dissimulation: and yet it is not to be said that there was sin in Christ or Abraham. Therefore not all dissimulation is a sin.
2. Further, no sin is profitable. But according to Jerome, in his commentary on Ga 2,11, "When Peter [Vulg.: 'Cephas'] was come to Antioch:---The example of Jehu, king of Israel, who slew the priest of Baal, pretending that he desired to worship idols, should teach us that dissimulation is useful and sometimes to be employed"; and David "changed his countenance before" Achis, king of Geth (1S 21,13). Therefore not all dissimulation is a sin.
3. Further, good is contrary to evil. Therefore if it is evil to simulate good, it is good to simulate evil.
4. Further, 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." Now it pertains to dissimulation to hide one's sin. Therefore it is reprehensible sometimes not to simulate. But it is never reprehensible to avoid sin. Therefore dissimulation is not a sin.

On the contrary A gloss on Is 16,14, "In three years," etc., says: "Of the two evils it is less to sin openly than to simulate holiness." But to sin openly is always a sin. Therefore dissimulation is always a sin.
I answer that As stated above (Question [109], Article [3]; Question [110], Article [1]), it belongs to the virtue of truth to show oneself outwardly by outward signs to be such as one is. Now outward signs are not only words, but also deeds. Accordingly just as it is contrary to truth to signify by words something different from that which is in one's mind, so also is it contrary to truth to employ signs of deeds or things to signify the contrary of what is in oneself, and this is what is properly denoted by dissimulation. Consequently dissimulation is properly a lie told by the signs of outward deeds. Now it matters not whether one lie in word or in any other way, as stated above (Question [110], Article [1], Objection [2]). Wherefore, since every lie is a sin, as stated above (Question [110], Article [3]), it follows that also all dissimulation is a sin.

Reply to Objection: 1. As Augustine says (De Questions. Evang. ii), "To pretend is not always a lie: but only when the pretense has no signification, then it is a lie. When, however, our pretense refers to some signification, there is no lie, but a representation of the truth." And he cites figures of speech as an example, where a thing is "pretended," for we do not mean it to be taken literally but as a figure of something else that we wish to say. In this way our Lord "pretended He would go farther," because He acted as if wishing to go farther; in order to signify something figuratively either because He was far from their faith, according to Gregory (Hom. xxiii in ); or, as Augustine says (De Questions. Evang. ii), because, "as He was about to go farther away from them by ascending into heaven, He was, so to speak, held back on earth by their hospitality."Abraham also spoke figuratively. Wherefore Ambrose (De Abraham i) says that Abraham "foretold what he knew not": for he intended to return alone after sacrificing his son: but by his mouth the Lord expressed what He was about to do. It is evident therefore that neither dissembled.
2. Jerome employs the term "simulation" in a broad sense for any kind of pretense. David's change of countenance was a figurative pretense, as a gloss observes in commenting on the title of Ps 33, "I will bless the Lord at all times." There is no need to excuse Jehu's dissimulation from sin or lie, because he was a wicked man, since he departed not from the idolatry of Jeroboam (2R 10,29 2R 10,31). And yet he is praised withal and received an earthly reward from God, not for his dissimulation, but for his zeal in destroying the worship of Baal.
3. Some say that no one may pretend to be wicked, because no one pretends to be wicked by doing good deeds, and if he do evil deeds, he is evil. But this argument proves nothing. Because a man might pretend to be evil, by doing what is not evil in itself but has some appearance of evil: and nevertheless this dissimulation is evil, both because it is a lie, and because it gives scandal; and although he is wicked on this account, yet his wickedness is not the wickedness he simulates. And because dissimulation is evil in itself, its sinfulness is not derived from the thing simulated, whether this be good or evil.
4. Just as a man lies when he signifies by word that which he is not, yet lies not when he refrains from saying what he is, for this is sometimes lawful; so also does a man dissemble, when by outward signs of deeds or things he signifies that which he is not, yet he dissembles not if he omits to signify what he is. Hence one may hide one's sin without being guilty of dissimulation. It is thus that we must understand the saying of Jerome on the words of Isaias 3:9, that the "second remedy after shipwreck is to hide one's sin," lest, to wit, others be scandalized thereby.

Whether hypocrisy is the same as dissimulation?

Objection: 1. It seems that hypocrisy is not the same as dissimulation. For dissimulation consists in lying by deeds. But there may be hypocrisy in showing outwardly what one does inwardly, according to Mt 6,2, "When thou dost an alms-deed sound not a trumpet before thee, as the hypocrites do." Therefore hypocrisy is not the same as dissimulation.
2. Further, Gregory says (Moral. xxxi, 7): "Some there are who wear the habit of holiness, yet are unable to attain the merit of perfection. We must by no means deem these to have joined the ranks of the hypocrites, since it is one thing to sin from weakness, and another to sin from malice." Now those who wear the habit of holiness, without attaining the merit of perfection, are dissemblers, since the outward habit signifies works of perfection. Therefore dissimulation is not the same as hypocrisy.
3. Further, hypocrisy consists in the mere intention. For our Lord says of hypocrites (Mt 23,5) that "all their works they do for to be seen of men": and Gregory says (Moral. xxxi, 7) that "they never consider what it is that they do, but how by their every action they may please men." But dissimulation consists, not in the mere intention, but in the outward action: wherefore a gloss on Jb 36,13, "Dissemblers and crafty men prove the wrath of God," says that "the dissembler simulates one thing and does another: he pretends chastity, and delights in lewdness, he makes a show of poverty and fills his purse." Therefore hypocrisy is not the same as dissimulation.

On the contrary Isidore says (Etym. x): "'Hypocrite' is a Greek word corresponding to the Latin 'simulator,' for whereas he is evil within," he "shows himself outwardly as being good; (hypo) denoting falsehood, and (krisis), judgment."
I answer that As Isidore says (Etym. x), "the word hypocrite is derived from the appearance of those who come on to the stage with a disguised face, by changing the color of their complexion, so as to imitate the complexion of the person they simulate, at one time under the guise of a man, at another under the guise of a woman, so as to deceive the people in their acting." Hence Augustine says (De Serm. Dom. ii) that "just as hypocrites by simulating other persons act the parts of those they are not (since he that acts the part of Agamemnon is not that man himself but pretends to be), so too in the Church and in every department of human life, whoever wishes to seem what he is not is a hypocrite: for he pretends to be just without being so in reality."We must conclude, therefore, that hypocrisy is dissimulation, not, however, any form of dissimulation, but only when one person simulates another, as when a sinner simulates the person of a just man.

Reply to Objection: 1. The outward deed is a natural sign of the intention. Accordingly when a man does good works pertaining by their genus to the service of God, and seeks by their means to please, not God but man, he simulates a right intention which he has not. Wherefore Gregory says (Moral.) that "hypocrites make God's interests subservient to worldly purposes, since by making a show of saintly conduct they seek, not to turn men to God, but to draw to themselves the applause of their approval:" and so they make a lying pretense of having a good intention, which they have not, although they do not pretend to do a good deed without doing it.
2. The habit of holiness, for instance the religious or the clerical habit, signifies a state whereby one is bound to perform works of perfection. And so when a man puts on the habit of holiness, with the intention of entering the state of perfection, if he fail through weakness, he is not a dissembler or a hypocrite, because he is not bound to disclose his sin by laying aside the habit of holiness. If, however, he were to put on the habit of holiness in order to make a show of righteousness, he would be a hypocrite and a dissembler.
3. In dissimulation, as in a lie, there are two things: one by way of sign, the other by way of thing signified. Accordingly the evil intention in hypocrisy is considered as a thing signified, which does not tally with the sign: and the outward words, or deeds, or any sensible objects are considered in every dissimulation and lie as a sign.

Whether hypocrisy is contrary to the virtue of truth?

Objection: 1. It seems that hypocrisy is not contrary to the virtue of truth. For in dissimulation or hypocrisy there is a sign and a thing signified. Now with regard to neither of these does it seem to be opposed to any special virtue: for a hypocrite simulates any virtue, and by means of any virtuous deeds, such as fasting, prayer and alms deeds, as stated in Mt 6,1-18. Therefore hypocrisy is not specially opposed to the virtue of truth.
2. Further, all dissimulation seems to proceed from guile, wherefore it is opposed to simplicity. Now guile is opposed to prudence as above stated (Question [55], Article [4]). Therefore, hypocrisy which is dissimulation is not opposed to truth, but rather to prudence or simplicity.
3. Further, the species of moral acts is taken from their end. Now the end of hypocrisy is the acquisition of gain or vainglory: wherefore a gloss on Jb 27,8, "What is the hope of the hypocrite, if through covetousness he take by violence," says: "A hypocrite or, as the Latin has it, a dissimulator, is a covetous thief: for through desire of being honored for holiness, though guilty of wickedness, he steals praise for a life which is not his." [*The quotation is from St. Gregory's Moralia, Bk XVIII.] Therefore since covetousness or vainglory is not directly opposed to truth, it seems that neither is hypocrisy or dissimulation.

On the contrary All dissimulation is a lie, as stated above (Article [1]). Now a lie is directly opposed to truth. Therefore dissimulation or hypocrisy is also.
I answer that According to the Philosopher (Metaph. text. 13, 24, x), "contrariety is opposition as regards form," i.e. the specific form. Accordingly we must reply that dissimulation or hypocrisy may be opposed to a virtue in two ways, in one way directly, in another way indirectly. Its direct opposition or contrariety is to be considered with regard to the very species of the act, and this species depends on that act's proper object. Wherefore since hypocrisy is a kind of dissimulation, whereby a man simulates a character which is not his, as stated in the preceding article, it follows that it is directly opposed to truth whereby a man shows himself in life and speech to be what he is, as stated in Ethic. iv, 7.The indirect opposition or contrariety of hypocrisy may be considered in relation to any accident, for instance a remote end, or an instrument of action, or anything else of that kind.

Reply to Objection: 1. The hypocrite in simulating a virtue regards it as his end, not in respect of its existence, as though he wished to have it, but in respect of appearance, since he wishes to seem to have it. Hence his hypocrisy is not opposed to that virtue, but to truth, inasmuch as he wishes to deceive men with regard to that virtue. And he performs acts of that virtue, not as intending them for their own sake, but instrumentally, as signs of that virtue, wherefore his hypocrisy has not, on that account, a direct opposition to that virtue.
2. As stated above (Question [55], Articles [3],4,5), the vice directly opposed to prudence is cunning, to which it belongs to discover ways of achieving a purpose, that are apparent and not real: while it accomplishes that purpose, by guile in words, and by fraud in deeds: and it stands in relation to prudence, as guile and fraud to simplicity. Now guile and fraud are directed chiefly to deception, and sometimes secondarily to injury. Wherefore it belongs directly to simplicity to guard oneself from deception, and in this way the virtue of simplicity is the same as the virtue of truth as stated above (Question [109], Article [2], ad 4). There is, however, a mere logical difference between them, because by truth we mean the concordance between sign and thing signified, while simplicity indicates that one does not tend to different things, by intending one thing inwardly, and pretending another outwardly.
3. Gain or glory is the remote end of the dissembler as also of the liar. Hence it does not take its species from this end, but from the proximate end, which is to show oneself other than one is. Wherefore it sometimes happens to a man to pretend great things of himself, for no further purpose than the mere lust of hypocrisy, as the Philosopher says (Ethic. iv, 7), and as also we have said above with regard to lying (Question [110], Article [2]).

Summa Th. II-II EN Qu.110 a.2