Chapter X — On the defect of justice, and of judgment, in an assertory oath. Some little questions are resolved

I. It has been explained above what truth, justice, and judgment are necessary for any oath whatsoever. In the present chapter, however, we chiefly undertake to discuss whether, just as the defect of truth in an assertory oath is always a mortal sin, so too the defect of justice and of judgment, in the same oath, constitutes a mortal sin. And, to resolve certain difficulties concerning this, we propose the following questions.

II. Question I. Is the defect of justice in an assertory oath a mortal sin? Response: Before I answer directly, I note that someone can swear an unjust matter in two ways. First, when someone relates a wicked matter as true, for a just cause — for instance, when, for a good end, he confirms by oath a sin committed by himself, or by another. In this manner, one would honestly, and justly, swear an unjust and wicked matter. Second, when someone manifests a wicked matter for a wicked end — for example, if someone were to reveal the hidden crime of a neighbor, whose reputation would be gravely injured by such a revelation. In this way, one would swear an unjust matter in an unjust manner, and would use the oath as an instrument for confirming a wicked manifestation. In the first case, he would confirm the truth of an iniquity committed, urgent just cause pressing; in the second, he would confirm the wicked manifestation of a crime, impelled by malice alone.

III. To the question, the theologians of Salamanca respond (tract. 17, ch. 2, punct. 2, §1, n. 34), teaching, from Suárez, Sánchez, Palao, Tamburini, and Leander, that the defect of justice in an assertory oath is not a mortal, but a venial sin — unless the oath is taken up as an instrument of iniquity, in which case the sin would be mortal. They adduce an example. You reveal the true, but hidden, crime of your neighbor, from which his reputation suffers grave harm. Then, so as to render your defamation more certain, you confirm it by oath. Then, surely, you sin mortally — not only with the sin of defamation, but also with a sin against justice, an accompanying oath. If, however, you disclose your own sin out of boastfulness and deliberate delight, and at the same time confirm by oath that you committed that sin, you indeed sin mortally with the sin of complacency, but you do not sin mortally against the justice necessary to an oath, but only venially. Thus the theologians of Salamanca distinguish, with the authors they cite.

The opinion of Sotus (Bk. VIII, on justice and law, art. 3, concl. 2), of the second matter, however, of Toledo (Bk. IV, ch. 22, n. 10 and 11), of Ledesma (Vol. II, Summa, tract. 11, ch. 3, dub. 4), of Aragón (II-II, q. 89, art. 10) seems more probable to me — namely, that the defect of justice in an assertory oath is a mortal sin, when the swearer's assertion is such that it constitutes a mortal sin; but if the assertion is only venial, the crime of the oath will likewise be venial. The reason seems manifest: because a most grave injury is done to God, when his authority is employed to confirm an assertion gravely wicked. And, to use the adversaries' own example, I do not see a disparate reason why they should say that one who confirms by oath a mortal complacency in his own sin does not sin mortally against the oath; while one who, by oath, makes another's infamy more certain, sins gravely against that same justice. Since, although, on the part of the sworn matter, it is a graver crime to defame one's neighbor than to delight in one's own iniquity already committed; nonetheless, on the part of the manner of swearing, as it is called, as often as God is brought forward as witness of a grave iniquity, a grave injury is done him.

Nor is the adversaries' response of any weight — namely, that, justice being lacking, the end of the oath still stands, which is the confirmation of truth; which standing, God is not called to witness of a lie, but of an iniquity. Since we too concede that the chief end of an oath is the confirmation of truth, or that truth is the foremost of the conditions necessary for a licit oath; and therefore we say that the defect of truth, even in the lightest matter, always induces a mortal sin; but the defect of the other two conditions, in a light matter, is only a venial sin. But from this it can in no way be inferred that the defect of justice, in a grave matter, is not a mortal sin. We conclude, then, that, whenever a swearer uses divine testimony for a bad end, or with a culpable and depraved mind, whether to strengthen a wicked manifestation, or of his own, or of another's mortal sin, he commits a double sin: one against the virtue to which the matter related is opposed; the other against the justice of the oath.

IV. Question II. Is the defect of judgment in an assertory oath a mortal sin? Response: We have spoken above of the judgment required for an assertory oath. This condition of judgment requires a reasonable cause for swearing: for whenever the reason, or cause, of swearing is lacking, the oath lacks judgment, as has been said. We have also produced, above, ch. 8, n. 4, six causes of this necessity from St. Thomas. Now we add that necessity, or the cause of this truth, or confirmation, is then present, when these two things concur. The first is that the truth cannot be proven by another way, except by the oath. The other is that it redounds either to the public, or the private, utility. The precise degree of this necessity cannot be prescribed, but it must be left to the judgment of a prudent man, when it really occurs, or is present. This is the general rule: that, without some moral utility, the necessity of swearing is never present.

V. So that we may answer the proposed question distinctly, however, a distinction must be admitted. If the matter which is to be sworn is manifestly true, and there is just, or licit, necessity of swearing, then, absolutely speaking, the defect of judgment in the inquiry of truth is only a venial fault. If, however, the defect of judgment is in this — that the oath is made without necessity — then a distinction must be made: if the negligence is light, the fault will be light; if the negligence is grave, it will be a mortal sin. The response is clear from what has been said above.