Thomas Aquinas, Summa Theologiae

Objection 1: It would seem that not all perjury is a mortal sin. It is laid down (Extra, De Jurejur, cap. Verum): "Referring to the question whether an oath is binding on those who have taken one in order to safeguard their life and possessions, we have no other mind than that which our predecessors the Roman Pontiffs are known to have had, and who absolved such persons from the obligations of their oath. Henceforth, that discretion may be observed, and in order to avoid occasions of perjury, let them not be told expressly not to keep their oath: but if they should not keep it, they are not for this reason to be punished as for a mortal sin." Therefore not all perjury is a mortal sin.

Objection 2: Further, as Chrysostom says, "it is a greater thing to swear by God than by the Gospels." Now it is not always a mortal sin to swear by God to something false; for instance, if we were to employ such an oath in fun or by a slip of the tongue in the course of an ordinary conversation. Therefore neither is it always a mortal sin to break an oath that has been taken solemnly on the Gospels.

Objection 3: Further, according to the Law a man incurs infamy through committing perjury (VI, qu. i, cap. Infames). Now it would seem that infamy is not incurred through any kind of perjury, as it is prescribed in the case of a declaratory oath violated by perjury . Therefore, seemingly, not all perjury is a mortal sin.

On the contrary, Every sin that is contrary to a divine precept is a mortal sin. Now perjury is contrary to a divine precept, for it is written (Lev. 19:12): "Thou shalt not swear falsely by My name." Therefore it is a mortal sin.

I answer that, According to the teaching of the Philosopher (Poster. i, 2), "that which causes a thing to be such is yet more so." Now we know that an action which is, by reason of its very nature, a venial sin, or even a good action, is a mortal sin if it be done out of contempt of God. Wherefore any action that of its nature, implies contempt of God is a mortal sin. Now perjury, of its very nature implies contempt of God, since, as stated above (Article 2), the reason why it is sinful is because it is an act of irreverence towards God. Therefore it is manifest that perjury, of its very nature, is a mortal sin.

Reply to Objection 1: As stated above (Question 89, Article 7, ad 3), coercion does not deprive a promissory oath of its binding force, as regards that which can be done lawfully. Wherefore he who fails to fulfil an oath which he took under coercion is guilty of perjury and sins mortally. Nevertheless the Sovereign Pontiff can, by his authority, absolve a man from an obligation even of an oath, especially if the latter should have been coerced into taking the oath through such fear as may overcome a high-principled man.

When, however, it is said that these persons are not to be punished as for a mortal sin, this does not mean that they are not guilty of mortal sin, but that a lesser punishment is to be inflicted on them.

Reply to Objection 2: He that swears falsely in fun is nonetheless irreverent to God, indeed, in a way, he is more so, and consequently is not excused from mortal sin. He that swears falsely by a slip of tongue, if he adverts to the fact that he is swearing, and that he is swearing to something false, is not excused from mortal sin, as neither is he excused from contempt of God. If, however, he does not advert to this, he would seem to have no intention of swearing, and consequently is excused from the sin of perjury.

It is, however, a more grievous sin to swear solemnly by the Gospels, than to swear by God in ordinary conversation, both on account of scandal and on account of the greater deliberation. But if we consider them equally in comparison with one another, it is more grievous to commit perjury in swearing by God than in swearing by the Gospels.

Reply to Objection 3: Not every sin makes a man infamous in the eye of the law. Wherefore, if a man who has sworn falsely in a declaratory oath be not infamous in the eye of the law, but only when he has been so declared by sentence in a court of law, it does not follow that he has not sinned mortally. The reason why the law attaches infamy rather to one who breaks a promissory oath taken solemnly is that he still has it in his power after he has sworn to substantiate his oath, which is not the case in a declaratory oath.

Articulus 3

Argumentum 1

Ad tertium sic proceditur. Videtur quod non omne periurium sit peccatum mortale.

Dicitur enim extra, de iureiurando, in ea quaestione quae ponitur, an a sacramenti vinculo absolvantur qui illud inviti pro vita et rebus servandis fecerunt, nihil aliud arbitramur quam quod antecessores nostri Romani pontifices arbitrati fuisse noscuntur, qui tales a iuramenti nexibus absolverunt. Ceterum ut agatur consultius, et auferatur materia deierandi, non eis ita expresse dicatur ut iuramenta non servent, sed si non ea attenderint, non ob hoc sunt tanquam pro mortali crimine puniendi.

Non ergo omne periurium est peccatum mortale.

Argumentum 2

Praeterea, sicut chrysostomus dicit, maius est iurare per deum quam per evangelium.

Sed non semper mortaliter peccat ille qui per deum iurat aliquod falsum, puta si ex ioco, vel ex lapsu linguae, aliquis tali iuramento in communi sermone utatur. Ergo nec etiam si aliquis frangat iuramentum quod solemniter per evangelium iurat, semper erit peccatum mortale.

Argumentum 3

Praeterea, secundum iura propter periurium aliquis incurrit infamiam, ut habetur VI, qu. I, cap.

Infames. Non autem videtur quod propter quodlibet periurium aliquis infamiam incurrat, sicut dicitur de assertorio iuramento violato per periurium.

Ergo videtur quod non omne periurium sit peccatum mortale.

Sed Contra

Sed contra, omne peccatum quod contrariatur praecepto divino est peccatum mortale. Sed periurium contrariatur praecepto divino, dicitur enim Levit. XIX, non periurabis in nomine meo.

Ergo est peccatum mortale.

Corpus

Respondeo dicendum quod, secundum doctrinam philosophi, propter quod unumquodque, illud magis.

Videmus autem quod ea quae, si de se sint peccata venialia, vel etiam bona ex genere, si in contemptum dei fiant, sunt peccata mortalia. Unde multo magis quidquid est quod de sui ratione pertinet ad contemptum dei, est peccatum mortale. Periurium autem de sui ratione importat contemptum dei, ex hoc enim habet rationem culpae, ut dictum est, quia ad irreverentiam dei pertinet.

Unde manifestum est quod periurium ex suo genere est peccatum mortale.

Ad 1

Ad primum ergo dicendum quod, sicut supra dictum est, coactio non aufert iuramento promissorio vim obligandi respectu eius quod licite fieri potest. Et ideo si aliquis non impleat quod coactus iuravit, nihilominus periurium incurrit et mortaliter peccat. Potest tamen per auctoritatem summi pontificis ab obligatione iuramenti absolvi, praesertim si coactus fuerit tali metu qui cadere posset in constantem virum. Quod autem dicitur quod non sunt tales puniendi tanquam pro mortali crimine, non hoc ideo dicitur quia non peccent mortaliter, sed quia poena eis minor infligitur.

Ad 2

Ad secundum dicendum quod ille qui iocose periurat, non evitat divinam irreverentiam, sed quantum ad aliquid magis auget.

Et ideo non excusatur a peccato mortali. Ille autem qui ex lapsu linguae falsum iurat, si quidem advertat se iurare et falsum esse quod iurat, non excusatur a peccato mortali, sicut nec a dei contemptu. Si autem hoc non advertat, non videtur habere intentionem iurandi, et ideo a crimine periurii excusatur.

Est autem gravius peccatum si quis solemniter iuret per evangelium quam si per deum in communi sermone iuret, tum propter scandalum; tum propter maiorem deliberationem. Quibus aequaliter hinc inde positis, gravius est si quis per deum iurans periuret quam si periuret iurans per evangelium.

Ad 3

Ad tertium dicendum quod non propter quodlibet peccatum mortale aliquis infamis efficitur ipso iure. Unde non sequitur, si ille qui iurat falsum iuramento assertorio non est infamis ipso iure, sed solum per sententiam definitivam latam contra eum in causa accusationis, quod propter hoc non peccet mortaliter. Ideo autem magis reputatur infamis ipso iure qui frangit iuramentum promissorium solemniter factum, quia in eius potestate remanet, postquam iuravit, ut det suo iuramento veritatem, quod non contingit in iuramento assertorio.