Thomas Aquinas, Summa Theologiae

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 (Wis. 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 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."

Reply to Objection 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; 1.2, 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.

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 Jn. 3:4): "Every 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 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.

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.

Articulus 4

Argumentum 1

Ad quartum sic proceditur. Videtur quod omne mendacium sit peccatum mortale.

Dicitur enim in psalm., perdes omnes qui loquuntur mendacium, et Sap. I, os quod mentitur occidit animam.

Sed perditio et mors animae non est nisi per peccatum mortale.

Ergo omne mendacium est peccatum mortale.

Argumentum 2

Praeterea, omne quod est contra praeceptum Decalogi est peccatum mortale. Sed mendacium est contra hoc praeceptum Decalogi, non falsum testimonium dices. Ergo omne mendacium est peccatum mortale

Argumentum 3

Praeterea, Augustinus dicit, in I de doct. Christ., nemo mentiens, in eo quod mentitur, servat fidem, nam hoc utique vult, ut cui mentitur fidem sibi habeat, quam tamen ei mentiendo non servat. Omnis autem fidei violator iniquus est.

Nullus autem dicitur fidei violator vel iniquus propter peccatum veniale. Ergo nullum mendacium est peccatum veniale.

Argumentum 4

Praeterea, merces aeterna non perditur nisi pro peccato mortali.

Sed pro mendacio perditur merces aeterna, commutata in temporale, dicit enim Gregorius quod in remuneratione obstetricum cognoscitur quid mendacii culpa mereatur. Nam benignitatis earum merces, quae eis potuit in aeterna vita tribui, praemissa culpa mendacii, in terrenam est remunerationem declinata.

Ergo etiam mendacium officiosum, quale fuit obstetricum, quod videtur esse levissimum, est peccatum mortale.

Argumentum 5

Praeterea, Augustinus dicit, in libro contra mendacium, quod perfectorum praeceptum est omnino non solum non mentiri, sed nec velle mentiri.

Sed facere contra praeceptum est peccatum mortale. Ergo omne mendacium perfectorum est peccatum mortale. Pari ergo ratione et quorumlibet aliorum, alioquin essent peioris conditionis.

Sed Contra

Sed contra est quod Augustinus dicit, in V psalm., duo sunt genera mendaciorum in quibus non est magna culpa, sed tamen non sunt sine culpa, cum aut iocamur, aut proximo consulendo mentimur.

Sed omne peccatum mortale habet gravem culpam.

Ergo mendacium iocosum et officiosum non sunt peccata mortalia.

Corpus

Respondeo dicendum quod peccatum mortale proprie est quod repugnat caritati, per quam anima vivit deo coniuncta, ut dictum est.

Potest autem mendacium contrariari caritati tripliciter, uno modo, secundum se; alio modo, secundum finem intentum; tertio modo, per accidens. Secundum se quidem contrariatur caritati ex ipsa falsa significatione. Quae quidem si sit circa res divinas, contrariatur caritati dei, cuius veritatem aliquis tali mendacio occultat vel corrumpit. Unde huiusmodi mendacium non solum opponitur virtuti veritatis, sed etiam virtuti fidei et religionis. Et ideo hoc mendacium est gravissimum, et mortale.

Si vero falsa significatio sit circa aliquid cuius cognitio pertineat ad hominis bonum, puta quae pertinent ad perfectionem scientiae et informationem morum, tale mendacium, inquantum infert damnum falsae opinionis proximo, contrariatur caritati quantum ad dilectionem proximi. Unde est peccatum mortale.

Si vero sit falsa opinio ex mendacio generata circa aliquid de quo non referat utrum sic vel aliter cognoscatur, tunc ex tali mendacio non damnificatur proximus, sicut si aliquis fallatur in aliquibus particularibus contingentibus ad se non pertinentibus. Unde tale mendacium secundum se non est peccatum mortale.

Ratione vero finis intenti, aliquod mendacium contrariatur caritati, puta quod dicitur aut in iniuriam dei, quod semper est peccatum mortale, utpote religioni contrarium; aut in nocumentum proximi, quantum ad personam, divitias vel famam. Et hoc etiam est peccatum mortale, cum nocere proximo sit peccatum mortale; ex sola autem intentione peccati mortalis, aliquis mortaliter peccat.

Si vero finis intentus non sit contrarium caritati, nec mendacium secundum hanc rationem erit peccatum mortale, sicut apparet in mendacio iocoso, in quo intenditur aliqua levis delectatio; et in mendacio officioso, in quo intenditur etiam utilitas proximi. Per accidens autem potest contrariari caritati ratione scandali, vel cuiuscumque damni consequentis.

Et sic erit etiam peccatum mortale, dum scilicet aliquis non veretur propter scandalum publice mentiri.

Ad 1

Ad primum ergo dicendum quod auctoritates illae intelliguntur de mendacio pernicioso, ut Glossa exponit, super illud psalm., perdes omnes qui loquuntur mendacium.

Ad 2

Ad secundum dicendum quod, cum omnia praecepta Decalogi ordinentur ad dilectionem dei et proximi, sicut supra dictum est, intantum mendacium est contra praeceptum Decalogi inquantum est contra dilectionem dei et proximi. Unde signanter prohibetur contra proximum falsum testimonium.

Ad 3

Ad tertium dicendum quod etiam peccatum veniale largo modo potest dici iniquitas, inquantum est praeter aequitatem iustitiae.

Unde dicitur I Ioan. III, omne peccatum est iniquitas.

Et hoc modo loquitur Augustinus.

Ad 4

Ad quartum dicendum quod mendacium obstetricum potest dupliciter considerari. Uno modo, quantum ad effectum benevolentiae in Iudaeos, et quantum ad reverentiam divini timoris, ex quibus commendatur in eis indoles virtutis. Et sic debetur eis remuneratio aeterna. Unde Hieronymus exponit quod deus aedificavit illis domos spirituales.

Alio modo potest considerari quantum ad ipsum exteriorem actum mendacii. Quo quidem non potuerunt aeternam remunerationem mereri, sed forte aliquam remunerationem temporalem, cuius merito non repugnabat deformitas illius mendacii, sicut repugnabat merito remunerationis aeternae. Et sic intelligenda sunt verba Gregorii, non quod per illud mendacium mererentur amittere remunerationem aeternam quam iam ex praecedenti affectu meruerant, sicut ratio procedebat.

Ad 5

Ad quintum dicendum quod quidam dicunt quod perfectis viris omne mendacium est peccatum mortale.

Sed hoc irrationabiliter dicitur. Nulla enim circumstantia aggravat in infinitum nisi quae transfert in aliam speciem.

Circumstantia autem personae non trahit in aliam speciem, nisi forte ratione alicuius annexi, puta si sit contra votum ipsius; quod non potest dici de mendacio officioso vel iocoso.

Et ideo mendacium officiosum vel iocosum non est peccatum mortale in viris perfectis, nisi forte per accidens, ratione scandali.

Et ad hoc potest referri quod Augustinus dicit, perfectis esse praeceptum non solum non mentiri, sed nec velle mentiri.

Quamvis hoc Augustinus non assertive, sed sub dubitatione dicat, praemittit enim, nisi forte ita ut perfectorum etc..

Nec obstat quod ipsi ponuntur in statu conservandae veritatis qui ad veritatem tenentur ex suo officio in iudicio vel doctrina. Contra quae si mentiantur, erit mendacium quod est peccatum mortale. In aliis autem non oportet quod mortaliter peccent mentiendo.