Article Fourth. On Perjury

254. Perjury is taken in a twofold sense: strictly and properly it signifies a false oath, or one lacking truth; broadly it signifies any illicit oath, so that even an iniquitous oath, lacking justice, and an incautious oath, lacking judgment, are called perjury. The malice of each must be discussed.

Therefore perjury (Meineid) properly is: alpha. an assertory oath concerning a false thing which the one swearing knows to be false; beta. a promissory oath without the intention of fulfilling the thing promised or with the intention of not fulfilling it. If someone afterward culpably does not fulfill a thing seriously promised under oath, he does not properly commit perjury, but rather breach of oath (Eidbruch), although he also is customarily called perjured.

1. On perjury strictly taken. a. Perjury or a false oath is a sin grave from its whole genus: for he directly brings injury upon the veracity of God who asks that God by His supreme authority attest to a false thing; and this injury remains grave even if God is invoked in testimony of the slightest falsehood: for it is always insultingly supposed that God can be deceived or deceive.¹

b. All perjuries are of the same moral species: for just as diverse oaths do not differ specifically, so also their violations are of the same moral species.

Although execratory perjury can seem to be a double sin, against religion and against charity, nevertheless in reality it is a simple sin against religion: for no one is judged seriously to imprecate evil upon himself or his own; therefore he who utters execratory words inwardly trusts that God will not do this. Yet by these things it is not denied that execratory perjury is a double sin, both against religion and against charity toward oneself or against piety, if the perjurer seriously intends to imprecate evil upon himself or his own.

¹ Wherefore proposition 24 was condemned by Innocent XI: To call God as witness of a light lie is not such irreverence on account of which He would will or be able to condemn a man.

255. 2. On perjury broadly taken. a. An assertory oath which lacks justice, insofar as it is an oath or insofar as it is opposed to religion, is venial, even if the sin against charity or justice is grave, as if someone confirms grave detraction by oath: for by this perjury grave irreverence is not committed, since God is not invoked in testimony of a false thing, but of a true thing, although evil.

b. A promissory oath lacking justice, by which someone obligates himself to a gravely evil thing, is a grave sin; by which he obligates himself to a lightly evil thing, a light sin; by which he obligates himself to an indifferent or useless thing, likewise a light sin.

Therefore in an oath of this kind (supposing the will of fulfilling it) two sins are contained, one because the one swearing (for example, that he will commit a duel) wills an evil thing, the other of irreverence, because with divine authority interposed he obligates himself to sinning.

c. An oath, whether assertory or promissory, which lacks judgment, or to swear without sufficient cause or without due reverence, does not exceed venial sin: for the irreverence does not seem to be grave, because nothing is done which is directly opposed to some divine attribute.

alpha. The faithful must be seriously admonished not to contract the habit of swearing rashly at nearly any doubt which is objected to their sayings, or of indiscriminately confirming their promises by oath: for those who contract and retain this habit expose themselves to the great danger of swearing without consideration of the things which they swear, and thus of making many perjuries.

beta. An oath uttered from the habit of swearing, if it is voluntary, of itself is only a light sin, because it is an oath lacking judgment; but by reason of the danger which it contains of committing perjury it can be a grave sin. Therefore the faithful are to be admonished concerning the obligation of laying aside the depraved habit of swearing, as was noted above (n. 205) concerning blasphemy.

256. On a fictitious oath. A fictitious oath is an oath made only externally, without the mind of swearing or without the mind of invoking God as witness of the assertion. Two things must be declared concerning this oath: a. whether it induces obligation; b. what kind of sin it is.

1. A fictitious oath, whether assertory or promissory, is no oath and accordingly induces no obligation from the virtue of religion; but from another source there can be present an obligation of keeping unharmed him who has been deceived by the fictitious oath.

2. a. A fictitious oath which is made in confirmation of a falsehood is always a grave sin, because it is grave irreverence to invoke God, even only externally, in testimony of a falsehood, just as it is grave irreverence only externally to burn incense to an idol.

An assertory oath is made in confirmation of a falsehood if the one swearing externally invokes God as witness of a false assertion; and a promissory oath, if he swears externally without the mind of fulfilling.

b. A fictitious oath which is made in confirmation of a truth does not exceed venial sin: for although an oath of this kind contains a lie with vain invocation of the divine name, nevertheless God is not invoked in testimony of falsehood.¹

Yet from another source the one swearing fictitiously can sin gravely, namely if he swears fictitiously in those circumstances in which he is held under grave obligation to swear, for example because of the precept of a superior or judge, or if there is question of a matter of great moment, such as an onerous contract.²

¹ Cf. Reuter, II, n. 309 ff.

² Cf. Lessius, De iustitia et iure, l. 2, c. 42, n. 42.