Question Two: On Perjury

S. Th. II-II, q. 98.

795. Perjury (parjure; meineed) is a perverse or vicious oath.

One kind is 1. strictly and properly so called, which imports falsity and is maximally perverse, because it is directly opposed to the end of an oath, which is the confirmation of truth: namely, it is a false oath which essentially lacks formal truth, or a lie confirmed by oath (faux serment; valsche eed).

Another kind is 2. taken broadly and generally, and is every illicit oath, or one deprived of one of the three required conditions or companions, namely:

a) A vain and incautious oath, if only judgment of discretion is lacking (serment indiscret ou vain; onbezonnen eed).

b) Or an iniquitous or dishonest oath, if justice is lacking (serment malhonnete; oneerlijke eed).

These are indirectly opposed to the end of an oath and to truth: "for in whatever mode someone swears something illicit, from this he incurs a certain falsity, because he is obliged to do the contrary... and when he swears indiscreetly, by this very fact he commits himself to the danger of incurring falsity" (a. 1, ad 1).

c) Indeed also if truth of future execution is lacking in a promissory oath (violation de serment; eedschending): nevertheless this is rather a sin of omission than a sin contrary to the oath and a perverse oath.

But if the aforesaid conditions are lacking in a fictitious oath, there is simulated perjury, which is a sin of the same species because the external irreverence toward God is the same.

796. Perjury strictly so called, or a lying oath, is a mortal sin from its whole genus, as is clear from proposition 24 condemned by Innocent XI,¹ and from the nature of the thing, because it is directly contrary to the divine attribute of infinite truth: for always he who swears a lie, even the lightest, appeals to God Himself, infinite truth, as witness of falsehood, as if either He did not know the truth, or could lie and wished to testify to falsehood; whence he contemns God and, so far as in him lies, destroys infinite truth, and at the same time evacuates the end of an oath, of confirming truth (a. 2 and 3).

¹ "To call God as witness of a light lie is not so great an irreverence on account of which He would will or be able to damn a man."

Hence God punishes it most severely (Lev. XIX, 12; Zach. V, 3, 4; Prov. VI, 16-19; Eccli. XXIII, 11; Mt. V, 33), and the Code of law says that it is to be punished (can. 2323), whence in several places solemn perjury is a sin reserved to the Ordinary.

797. Perjury improperly so called from defect of judgment alone, or an incautious oath, that is, without due cause of swearing, is a sin (Ex. XX, 7; Deut. V, 11; Eccli. XXIII, 9, 16; Mt. V, 34), but, if the other conditions are present, it is only venial, scandal, contempt, and danger of another grave defect being excluded: for it is not directly to act against some divine attribute, but only to act irreverently with the divine majesty, by using His name in vain.

798. Perjury improperly so called from defect of justice, or an iniquitous oath:

1. If it is merely assertory, per se it is probably only venial, because the oath does not fall upon the assertion insofar as it is evil but insofar as it is true; whence it does not destroy the end of the oath, nor make God witness of a lie, but of a depraved or indecent thing, which per se does not appear to be a grave injury, unless the oath is employed as a means or instrument of sinning, for example, for conciliating greater faith to detraction, or in attestation of depraved love for seducing a girl: for this, so far as in itself lies, is to make God a cooperator of iniquity.

2. If the oath is promissory:

a) To swear a gravely illicit action, without doubt and with all consenting, is always a mortal sin.

b) Likewise to swear even a lightly illicit action is mortal from its whole genus, for it seems a grave irreverence to call God as witness and patron, so that by His authority He may confirm the purpose of committing any evil whatsoever, even the lightest, because it is directly repugnant to His infinite sanctity; nevertheless per accidens, because of ignorance, it will often be venial.

c) On the contrary, to swear an indifferent, vain, useless, or idle action, or one impeditive of a greater good, contempt being excluded, is only venial: it is to assume the name of God in vain.

799. Observations. - 1. In a promissory oath there is perjury strictly so called and always mortal sin if the one swearing is without the intention of fulfilling the promise; likewise one swearing an impossible thing, because he cannot have this intention of fulfilling, for example, a debtor who swears that he will pay the price within a month and knows certainly that he cannot.

2. A custom or habit of swearing is evil, because, as a proximate occasion, it inclines to sins, namely, false, dishonest, vain oaths. Whence there is an obligation of removing it (Eccli. XXIII, 9 sq.; Mt. V, 34), and he sins who voluntarily acquires such a habit, or neglects to eliminate it: interiorly and as to affection, as often as, adverting to the obligation of retracting the habit, he does not retract it; exteriorly and as to effect, as often as from the habit he utters sufficiently foreseen vicious oaths by morally interrupted acts. But he sins gravely if from custom he is disposed to swear anything indiscriminately, even false and gravely dishonest things; venially if he is disposed only to swear vain or lightly dishonest things.

He who swears from custom either a) attends to the act of swearing and to the defect of the conditions required for it, and then the vicious oath is voluntary in itself; or b) attends only to the act of swearing and not to its defect, and then the oath is gravely or lightly culpable in its cause, namely, in the custom, as was said; or c) attends to nothing, and then properly he does not swear, because the intention of swearing is lacking, but the speech can be culpable in its cause, insofar as externally it sounds like an evil oath or at least a vain use of the name of God; d) but if he has retracted the custom, the oath will not be voluntary even in its cause.

3. To ask for an oath with defect of truth, justice, or judgment a) is not licit, if it cannot be furnished without such defect, because it would be directly to induce to sin, for example, to ask that someone swear falsely or by false gods. b) Nor is it licit if the other does not advert to the defect and sins only materially, or if he swears what he thinks is true, although in fact it is false, because the one asking is the true moral cause of the oath; but the ignorance of the one swearing cannot excuse him who knowingly asks that God be invoked as witness of a dishonest or false thing (Lev. V, 1). c) But it is licit, from a just and proportionate cause, to ask an oath from him who can swear well, but who probably or certainly will swear badly, for example, by false gods. But if the other is going to commit perjury strictly so called, there is easily a sufficient cause on account of the common good for a public person who from office ought to ask the oath, and besides "she does not seem to exact it, but he at whose instance she exacts it"; never or very rarely for private persons, because regularly it would be to give an occasion of sinning without hope of some good (a. 4, and ad 4).