Chapter III — On the matter of a promissory oath, which induces an obligation

I. What we are about to say in this chapter is easy, and open to all — since those things which we have said above concerning this matter will dispatch the whole business in a few words. A promissory oath requires two conditions to be subjected to the matter: first, that it be lawful; second, that it be possible, and good.

II. By the term "lawful matter" are understood not only spiritual things, namely acts of piety, of religion, of faith, and similar ones; but also all human affairs and business, commerce, covenants, and contracts, provided they concur... with the three conditions already explained. Hence the error of Wycliffe was condemned in the Council of Constance, who denied that it is lawful to confirm human contracts and civil commerce by oath. But of this enough has already been said.

III. From this it follows, first, that all those matters which are illicit, shameful, and culpable are excluded, since the matter of an oath ought to be lawful. The reason is manifest: because an oath is not a bond of iniquity, as all things proclaim. Wherefore an oath to commit a venial sin does not oblige in any way. And although in the chapter "Cum contingat," on the law of oaths, it is established that every oath is to be kept, unless it turns to the detriment of eternal salvation, it does not therefore follow that a venial sin may be committed. For, granted that it is lawful to commit a venial sin confirmed by oath, and that this in some way closes the door of eternal life; since, unless one is purged of it either in this or in the future age, no one attains the reward of eternal life — no oath, then, obliges to the observance of that which cannot be fulfilled without either mortal or venial sin. When, however, the sworn matter is partly lawful, partly illicit, the illicit part must be omitted; the lawful and good part, however, must be observed.

IV. Not only must the matter of a promissory oath be lawful, but possible, so that it may give rise to the obligation of execution. Wherefore an oath concerning impossible matters is rash, and empty. Those, then, sin, who promise another's deed under oath, since one cannot compel another's will. It must be observed, however, that men often, in promising another's deed, swear their own deed — for example, if you swear that Peter will marry his betrothed Bertha, or that he will pay Paul a sum of money, or other things of this kind — according to common sense, you do not swear another's deed, but your own — namely, that you will use every effort to bring it about that Peter contracts the marriage, so that he pays what is owed, etc. Hence jurists teach that such an oath has a twofold force: that it is valid in one way, if it can be fulfilled in the manner in which it sounds; in another way, if the deed of another sworn cannot be fulfilled in that manner, it is valid in whatever manner it can be. It can be sworn concerning another's deed in a twofold manner. First, enunciatively — as when you swear that you believe a sick man will regain his former health, or that tomorrow the sky will be clear. Second, under a promise, in which case you are bound to apply your effort and diligence, so that what you promised may happen, or come to pass. In these oaths concerning another's deed, authors commonly teach that the swearer is bound to diligence and effort, when the deed which is sworn is capable of diligence; but not so, when it is not established that he swore only enunciatively, that he believes it — since, if it were established that the oath was only enunciative, he would be bound to nothing.

V. It has been said that the matter of a promissory oath ought to be lawful, possible, and good. This last little word has been added, so that indifferent matter may be excluded — since an oath concerning an indifferent matter produces no obligation: both because God does not oblige to idle and vain acts, of which kind indifferent acts are; and because the exercise of an indifferent act, without reference to an honorable end, is always a venial sin, as the truer opinion teaches. And although, according to another opinion, it is not, for that reason, unfit matter for an oath — and this suffices, lest it be a vicious act.

VI. If, however, an indifferent act is directed toward an honorable end, or utility, the oath obliges — since an indifferent act, in the individual, though otherwise useless, on account of an honorable end, becomes an act of virtue. I add: when the oath is for the utility of one's neighbor, it must be observed, even though the matter sworn is indifferent, provided it is not evil in itself. The reason is that, in this case, what is primarily intended is not the indifference of the act, but the utility and advantage of the neighbor himself. Indeed, the observance of such an oath becomes an act of virtue — for it is an act of fidelity, and of veracity — and, beyond this, once the promise has been made and accepted by the neighbor, he already acquires a certain right, by force of which the swearer is bound to fulfill the promise. All this is established, and common among all. The same must be said of an oath which pertains to the swearer himself. For example: you swore that you would in no way pass through this way, because passage through it is an occasion of sin for you: although such passage, absolutely, is an indifferent act, nonetheless, clothed with such a circumstance, it becomes a good act.

VII. This too is worth noting: namely, that the matter of an oath made to God is different from the matter of an oath which is made in favor of one's neighbor. For an oath made to God agrees with a vow only in this: that it ought to be lawful and honorable; but such matter ought not to be merely good, but that which is a greater good. For a lesser good does not oblige, which cannot conduce to the grace of God. It must be judged otherwise concerning an oath made in favor of one's neighbor — for whom it is not always the greater good that pleases, but often that which is more pleasing to him. Therefore an oath concerning a lesser good, in favor of one's neighbor, obliges.

VIII. From this teaching, however, is excepted a promise confirmed by oath of contracting marriage — since this promise always includes this condition, unless I should choose a better state, namely, the religious one, as the Doctors commonly teach on the chapter "Ex publico," on the conversion of spouses. Nor does the text stand in the way, in the chapter "Cum eam," on him who had promised by oath a marriage arranged for his betrothed, where it seems to be established that a man who has sworn to take a woman in marriage cannot enter religious life unless the marriage is first contracted. For such a swearer can indeed contract marriage with the resolve of not consummating it, but of entering religious life, the bride being ignorant of such a resolve — as Suárez notes, and teaches (Bk. II, on the oath, ch. 13, n. 8) — which manner is lawful, though scarcely to be advised in practice, since it does not seem consonant with the bride's honor. For by this path she is rather deluded. As for the Pontiff's saying, in the cited chapter, that it is safer, the religion of the oath being observed, to contract marriage first, and then to migrate to religious life — this pertains to the fact that perhaps, in that case, such a contract redounded to the bride's honor, and therefore the Pontiff said it was safer to observe such a manner — not that it was unsafe to do otherwise; for, as I said, then it was perhaps better to observe such a manner. For the rest, since the condition of a better state is included in the promise, it follows that the oath ought to take on the nature of the act to which it is joined. The condition, then, included in the act of promise, is understood as included in the oath as well. Wherefore a betrothed man who has sworn can, without the bride's consent, and without a marriage contract, enter religious life. In practice, however, that manner is to be observed which is convenient, and which accords with the bride's honor, and does not impede entrance into religious life. It should be observed, however, that the Pontiff calls it "safer" and "momentary," not "safe" absolutely. If both cannot be observed, the taking up of the religious state ought to be preferred; provided that, in embracing the religious state, real regular observance flourishes.

IX. In the last place, it can be doubted whether an oath made concerning an unlawful matter needs relaxation. But the Doctors commonly teach that no relaxation is needed. For where there is no bond, no relaxation is necessary. But an oath, since it is not a bond of iniquity, produces no obligation whenever it concerns an unlawful matter. Nor does that stand in the way which is customarily opposed from the chapter "Venerabilem," on elections, §"Idem," where, concerning a certain usurper of a kingdom, contrary to an oath made, it is related that he ought to have consulted the Apostolic See — since it was doubtful whether or not that oath had been made concerning an unlawful matter. To the other objection, which is customarily raised from the chapter "Cum quidam," on the law of oaths, §"Illi vero," where it is decreed that sons are to be absolved from an oath of not speaking to, or aiding, their father and mother — we say, with the same author, that the word "absolve," in that text, signifies a declaration of the solution, or that it declares that oath to have been from the beginning null and void; various other solutions being set aside, which Suárez reports (Bk. II, on the oath, ch. 15, n. 18) — that oath, I say, was in no way truly binding, but only declaratory of the fact that no obligation existed; it did not truly dissolve the bond of an obligation.