§ 3. On the Promissory Oath

Preliminary note. The promissory oath must be treated specially, because it differs from the assertory in this, that it not only asserts something concerning the present, but besides affirms something concerning the future, namely accurate execution of the thing promised.

614. PRINCIPLES. I. A promissory oath concerning a licit and useful thing induces an obligation of religion. For through an oath God is invoked not only as witness of truth in promising, but also as surety for faithful execution of the thing promised. Therefore oath truly induces an obligation of executing what was promised, on account of reverence for the divine name, or an obligation of religion (cf. Lehmkuhl, I, 562, note; Schindler, II, p. 165).

It was said: 1. An oath concerning a licit thing, etc.; because if it is concerning an illicit thing, or a thing of no utility, it induces no obligation. For an oath, as being an act of religion, cannot be a bond of iniquity, or of an idle thing which does not fall to the honor of God. Indeed, he sins gravely who promises illicit things by swearing. But neither does an oath become valid, even if such an illicit and vain thing, the circumstances afterward being changed, becomes honorable; since that is not strengthened by lapse of time which did not subsist in the beginning (III, 176).

But if the thing promised is less good and against the evangelical counsels, one must distinguish: either the promise was made to God alone, or for the utility of a man. In the first case there is no obligation, because the thing promised to God ought not to be impeditive of a greater good: thus, for example, he who had sworn that he would never fast outside the days established by the Church can nevertheless fast. - In the second case, if the promise was accepted and can be kept without sin, the oath must be stood by. The reason is that any promise concerning a licit and possible thing, and useful to a third party, must be fulfilled at least from fidelity (cf. n. 1062). Thus, for example, he who swore to a girl that he would enter matrimony with her is held to accept her as wife, unless he wishes to enter Religion: which is conceded to him from a special disposition of law (III, 173; H. Ap., V, 13). Thus also a priest who swore that he would not leave the diocese cannot, without dispensation, enter Religion (III, 177).²

2. It induces an obligation of religion. Here it must be noted: a) He who violates this obligation by not fulfilling what he swore does not indeed commit perjury strictly so called, but sins by irreverence toward God, by despising his authority, which had been brought forward for strengthening the promise. b) The obligation which arises from an oath, since it is an obligation of religion, is altogether personal and does not pass to heirs. Wherefore these persons, indeed by force of the oath and from religion, are not held to fulfill it, even if perhaps they are held by another title, for example from pact and justice. c) A fictitious oath does not induce an obligation of religion, since it is null; nevertheless it can well oblige so that scandal or harm to another may be avoided (III, 172, 177).

II. A promissory oath obliges under grave or under light matter, according to the gravity of the thing promised. The obligation of an oath is ordinarily less than the obligation of a vow; but a vow, in light matter, obliges only under light matter. St. Thomas, 2.2, q. 89, a. 8; Lehmkuhl, I, 562. See St. Alph., III, 173; Vind. Alph., I, p. 227.

III. A promissory oath has the same condition and the same mode of interpreting as the promise or purpose to which it is annexed. The accessory follows the principal; and therefore when the promise does not oblige, neither does the oath attached to it oblige (III, 180).

615. Since therefore an oath claims for itself the same conditions and mode of interpreting as the promise to which it is added, this TWO-FOLD RULE can be established:

RULE 1. The obligation of an oath is of strict interpretation, namely so that the one swearing is considered to have wished to oblige himself as little as he could. For thus promises and contracts must be interpreted.

Therefore, if some act or contract does not subsist from the beginning, whether because it is invalid by its nature, for example because of equivocation employed in promising or in contracting, or because it is void from positive law on account of the common good, it follows that no obligation comes from the oath either. Thus an oath extorted by fear does not oblige concerning profession, matrimony, espousals, renunciation of the ecclesiastical forum, donation made by a cleric to a concubine (III, 177).

RULE 2. Every oath must be interpreted according to the CONDITIONS which, by fiction of law, are tacitly understood.

But they are the following: a) If I shall be able, that is, if the promise can be fulfilled without grave harm. b) Saving the right of the Superior, that is, if the Superior does not prohibit execution. c) If the state of things has not been notably changed. d) If the other part also has kept faith in a mutual obligation. e) If the promisee does not yield his right. f) If the final cause, on account of which the promise was made, does not cease (III, 180, 187; H. Ap., V, 18).

616. From these things you will deduce: 1. An oath of observing the statutes of some congregation, college, etc., is to be interpreted thus: a) that it is understood concerning statutes published, not to be published; b) that it is understood to oblige under grave or light matter, or only to penalty, or only under counsel, just as the statute itself obliges; c) that it does not oblige to statutes which have lost the force of obliging, on account of impossibility, or desuetude, or because they have thus been received in use; d) that it also does not oblige if some statute is not observed by the greater part of the community (III, 181). - Religious profession also, if it is invalid, is not strengthened through an annexed oath.

2. "He who swore that he would preserve a secret does not sin against the oath by revealing it when he cannot conceal it without grave harm to himself or another; because the very promise of secrecy does not seem to oblige except with this condition: if it does no harm. Similarly, the obligation of the oath ceases if the matter has become known from elsewhere" (III, 183).

3. He who swore to a judge that he would say the things which he knows is not held to reveal hidden things, because at least half-full proof of the crime must precede. Yet except cases which commonly do not admit except single witnesses, as, for example, the case of solicitation to shameful things (ibid., 5).

4. He who promised with an oath that he would return to prison, much more probably is held to return with probable fear of death or of most grave unjust harm; because, the promise having been posited, to return is a work of virtue. Yet others deny, because it would be an evil action voluntarily to offer oneself to death (cf. III, 186).

5. "Parents or masters swearing that they will punish children or servants rarely sin if they do not fulfill the oath; either because the delinquents have already been corrected, or because the oath was concerning a useless thing, or rather concerning disordered vengeance; or because such oaths are very often made without an intention of swearing, but only of frightening" (ibid.).

6. Generally, the oath not to sell for less or not to buy for more does not bind merchants; either because oaths of this sort are for the most part concerning a useless thing; or because these men do not have the intention of swearing; or certainly because there is in the oath a tacit condition, unless things seem to go better otherwise.

7. An oath of fidelity and obedience regards only those things which are comprehended in the office of the one swearing. Whence, by force of such an oath, an inferior cannot be held either to illicit things, or to impossible things, or to things too grave, or to things extrinsic to his office. See Lehmkuhl, I, 568. Cf. what was said n. 611, 4.

617. Questions. QUES. 1. Whether an oath ever obliges by which a promise void by law or to be voided at the discretion of the one promising is confirmed?

Resp. 1. It obliges if the promise is made void in favor of the one promising, and he, conscious of the matter, nevertheless swears. For one acting thus renounces his right and binds himself with the bond of religion, which, although it confers no right upon the promisee, ought to be kept on account of reverence for God. 2. It does not oblige if the promise is made void on account of the public good, because the thing promised then becomes illicit; nor does it oblige if the one swearing intends only to bind himself, by the bond of religion, to the proper and connatural obligation of the promise (III, 172, 3; 177). Cf. below n. 1059.

QUES. 2. Whether an oath emitted from deceit or ERROR obliges in conscience?

Resp. 1. It does not oblige, if the error or deceit turns upon the substance of the thing, or essential circumstances, or other circumstances sufficiently notable, which, if they had been foreknown, would have impeded the promissory oath; because then the thing promised is not considered sufficiently known for consent to be free. 2. But it obliges if the error or deceit turns upon circumstances altogether accidental (III, 175). - See n. 1061 ff.

QUES. 3. Whether an oath extorted by GRAVE and UNJUST FEAR obliges?

Resp. 1. In the EXTERNAL forum, where the mind of swearing is presumed to have been lacking, it certainly does not oblige. - 2. As regards the INTERNAL forum, it is disputed; but the more common and far more probable opinion, which also D. Thomas embraces with Suarez and Lugo, says that it obliges. Thus, for example, the oath of giving money or usury to a robber or usurer obliges. And the reason is that from religion we are held to effect that what we swear be true, lest we make God witness of falsity. The rule of law is consonant, according to which any oath whatsoever must be kept which can be kept without sin.³

Nevertheless: a) One suffering fear can swear with mental restriction, so that he contracts no obligation (n. 608, q. 2 and 615, Rule 1). b) If he truly promised, he can seek relaxation of the oath from the Bishop, or from another having faculty, so that he may be excused from the obligation of paying. c) If he has already paid, he can seek again in judgment what he gave, or compensate himself secretly (cf. n. 1059, q. 2). See St. Alph., III, 174; ed. G., I, 480.

The adversaries indeed say that a payment which can be sought again or secretly taken back is something ridiculous. But St. Alphonsus responds that the payment is not illusory, because there is always danger lest the thing handed over to the thief from fear cannot afterwards be sought again.

Note. 1. The obligation of an oath ceases intrinsically by cessation of the motive cause, that is, when the matter of the oath becomes either impossible, or useless, or harmful, or when a notable change or circumstance supervenes, which, if foreseen, the oath would not have been made (cf. n. 615, Rule 2; 625, 4).

2. It ceases extrinsically by irritation, dispensation, and commutation, just as a vow, because the same reason runs. It also ceases by remission of the obligation made by him in whose favor the sworn promise was emitted, because each one can yield his own right (III, 187-193).