Article II. On the Obligation of a Promissory Oath

I Say 1st. Every promissory oath concerning a licit and honorable thing, besides the obligation of fidelity or even of justice, also induces an obligation of religion; but it in no way obliges if it is concerning an illicit or plainly useless thing. The reason of the first is that, when a new bond imposed by a different virtue has been added, a new obligation ought to arise. But the reason of the second is that an oath, as an act of religion, cannot be a bond of iniquity or of an idle thing; nor does that oath afterward revive, even if the thing ceases to be idle or illicit, for according to the rule of law 18, in 6: "What does not subsist in law from the beginning is not made firm by the passage of time." - Cf. Baller., note (b), p. 307.

§ 1. He who freely swears that he will do something is held by a peculiar obligation of religion to fulfill what he has confirmed by oath (Can. 1317).

I Say 2nd. The obligation of an oath is to be interpreted strictly, and it follows the nature of the act or contract to which it is added, and all its conditions. The reason of the first is that one swearing is judged to have wished to oblige himself as little as he could; but the reason of the second is that an oath does not change the nature of the act, but superadds to it only the obligation of religion, and therefore ought to have the same conditions. - Besides, the obligation of an oath is to be interpreted according to the tacit conditions included or understood in it, which are: 1st, if I can without grave damage; 2nd, if the thing shall not have been notably changed; 3rd, if the rights or will of a superior do not stand in the way; 4th, if the other has kept reciprocal faith; 5th, unless the other yields concerning his right. - Cf. St. Alphonsus, n. 180.

§ 3. An oath taken neither by force nor by fraud, by which someone renounces a private good or favor granted to him by law, must be observed whenever it does not incline to the detriment of eternal salvation (Can. 1317).

I Say 3rd. § 1. A promissory oath follows the nature and conditions of the act to which it is added.

§ 2. If an oath is added to an act directly tending to the damage of others or to the prejudice of the public good or of eternal salvation, the act obtains no firmness from it (Can. 1318).

I Say 4th. An oath is to be interpreted strictly according to the law and according to the intention of the one swearing, or, if he acts by fraud, according to the intention of him to whom it is sworn (Can. 1321).

Question 1. Is there smallness of matter in the transgression of a promissory oath?

Response. Affirmatively, probably. For in a promissory oath two things are to be distinguished, namely the actual truth of the promise, or of the intention of carrying out the promise, and the future execution itself of the promise. Now God is indeed invoked as witness of the truth of the intention; but as regards the execution itself, he is brought forward only as guarantor, or as a person furnishing authority to the obligation which arises from the promise made before him and otherwise valid, just as a prince by his authority renders pacts contracted before him firmer. But since we now suppose that the intention of fulfilling the sworn promise was sincere, the malice of this transgression is to be measured not from injury toward the truthfulness of God, but only from irreverence inflicted upon his authority. But since this is not direct and formal, nor greater - indeed according to St. Thomas less - than that which is had in the transgression of a vow, it follows that smallness of matter can exist in the transgression of a promissory oath. - Cf. St. Alphonsus, n. 173; and Hom. Ap., n. 13. Baller., note (a), p. 308.

Question 2. Does a promissory oath emitted through error or fraud oblige?

Response. Negatively, if the error or fraud concerns the substance of the thing, because then a simple contract would be invalid; but if it affects only accidental circumstances, one must subdistinguish: it indeed obliges in onerous contracts, but not in gratuitous ones, at least probably, if the circumstances, although accidental, are nevertheless such that if they had been foreseen from the beginning, they would have deterred one from both the promise and the oath. - Cf. St. Alphonsus, n. 175. - Baller., note (b), p. 308.

Question 3. Does a promissory oath extorted by grave and unjust fear oblige?

Response. § 2. An oath extorted by force or grave fear is valid, but can be relaxed by an ecclesiastical Superior (Can. 1317).

Question 4. In what way does the obligation of an oath cease?

Response. The obligation induced by a promissory oath ceases:

1st. If it is remitted by him for whose advantage the oath had been emitted;

2nd. If the sworn thing is changed substantially, or, the circumstances having been changed, becomes either evil or altogether indifferent, or finally impedes a greater good;

3rd. If the final cause or condition under which perhaps the oath was given is lacking;

4th. By irritation, dispensation, commutation, according to the norm of can. 1320 (Can. 1319).

Question 5. Can he who has a delegated faculty of dispensing in vows also dispense in oaths?

Response. Affirmatively. Those who can irritate, dispense, or commute a vow have the same power and by the same reason concerning a promissory oath; but if the dispensation of the oath inclines to the prejudice of others who refuse to remit the obligation, only the Apostolic See can dispense the oath on account of necessity or the utility of the Church (Can. 1320).