Article I. On the Conditions Required for a Vow

The conditions required for the validity of a vow are contained in the very definition of a vow, and there are two principal ones, namely, true intention and suitable matter. Wherefore:

I Say 1st. For the validity of a vow there is required a true and deliberate intention of emitting a vow, or a true promise of itself suitable to inducing an obligation; for a vow is like a certain law, which the one vowing, otherwise capable of weighing the burden which he assumes, imposes upon himself. Hence a vow essentially differs from a proposal, because a proposal, however firm, does not produce a bond of obligation, nor is omission of the thing proposed a sin, except perhaps sometimes by accident, for example, on account of inconstancy, weariness, or negligence, which of themselves do not exceed venial sin. - Cf. St. Alphonsus, nn. 196 and following.

I Say 2nd. The matter of a vow ought to be not only morally possible, but also morally good, indeed better than its opposite. The reason of the first is that no one can oblige himself to something morally impossible to him; and the reason of the second is that God is not worshiped by an action whose placing is not better than omission. But a better good is here understood not only absolutely in itself, but also relatively to circumstances. - Cf. St. Alphonsus, n. 202.

I Say 3rd. § 1. A vow, that is, a deliberate and free promise made to God concerning a possible and better good, must be fulfilled from the virtue of religion.

§ 2. Unless they are prohibited by law, all possessing suitable use of reason are capable of a vow (Can. 1307).

Question 1. How great ought deliberation to be in emitting a vow?

Response. It is commonly taught by theologians that the deliberation which suffices for mortal sin suffices for a vow. But this is indeed so if in each case the relation of the deliberating mind to the object is considered; but if attention is given to the fact that it is more difficult to deliberate about some obligation to be assumed than about the violation of some law, it must be said that greater discretion of judgment or deliberation is required for emitting a vow than for perpetrating mortal sin. - Cf. Baller., note (c), p. 313.

Question 2. Is a vow valid which has been made with inadvertence to an obligation already known?

Response. Affirmatively, if he who emits the vow habitually knows clearly its obligation, although actually he does not attend to it; or also if he who vows, even if he does not know the obligation clearly, nevertheless apprehends it confusedly and wills it implicitly, while, for example, he wills to vow this or that, as others are accustomed to vow. - Nevertheless it must generally be held that no greater obligation is induced beyond that which someone wills to impose upon himself and has apprehended. - Cf. St. Alphonsus, n. 201.

Question 3. Is a vow emitted from error valid?

Response. Affirmatively, if the error regards accidental circumstances of lesser moment; for he who vows is judged to oblige himself to undergoing merely accidental inconveniences which can occur in fulfilling the vow. But one must answer otherwise if the error concerns the substance of the thing, or accidental circumstances indeed, but which are principally intended, or notably change the substance itself, or are of such a nature that, if they had been known, the vow would not have been emitted; for then the promised thing could not be said to be sufficiently known and willed. - Nevertheless vows emitted after the novitiate in any approved order must always be excepted; for these are not invalid except by error properly and strictly substantial. The reason is that otherwise they would not be sufficiently accommodated to the firmness which is essential to the religious state. - Cf. St. Alphonsus, n. 198. - Lugo, de jure et just., disp. 22, n. 88. - Baller., note (b), p. 314, and note (a), p. 315.

Question 4. Is a vow made through fear valid?

Response. Affirmatively, if the fear, however grave, provided it does not remove the use of reason, arises from within, or from a necessary extrinsic cause; for those things which are done from fear are simply voluntary. But can. 1307, § 3, says that a vow emitted from grave and unjust fear is null by the law itself. The reason is that the law of nature, which demands that an injured right be restored in its entirety, dictates that what is extorted from someone through injury cannot be acceptable to God. It is also clear from canon law as regards solemn vows of Religion, and more probably also as regards other vows, according to the more common interpretation of theologians. - I said if it is grave; for light fear never invalidates a vow, at least for the external forum. Cf. St. Alphonsus, n. 197. - Baller., note (b), p. 315.

Question 5. Is he who doubts whether he emitted a vow or a mere proposal held by the vow?

Response. Negatively, as is clear from what has been said concerning probabilism. Nevertheless it must be noted that if he who thus doubts believed, in promising, that he would sin if perhaps he did not carry out the proposed thing, it can be judged that he truly vowed. I say can, and not ought, because simple people who propose before a priest to recite some pious prayers at their proper time, or never to drink a certain kind of liquor, surely think that they would sin if afterward they violated that promise, and yet it is certain that they emit no vow. - Cf. Baller., note (a), p. 316.

Question 6. Is a vow not to sin valid?

Response. Affirmatively, if the vow regards all mortal sins or fully deliberate venial sins, or sins of a certain kind, for example, a vow never to lie. But a vow of avoiding all sins, even the very lightest, would not be valid, because without a special privilege this is impossible. Cf. Mazzella, de Gratia, disp. 2, art. 5.

Question 7. Is a vow concerning matter already commanded from elsewhere valid?

Response. Affirmatively, both because it is not repugnant for a debtor to be obliged by different titles, and because a vow of this kind concerns a thing good in itself, otherwise it could not have been commanded; it is also concerning a better good, since the new bond can contribute to greater fidelity and devotion in fulfilling the law. - Cf. St. Alphonsus, n. 203.

Question 8. Is a vow of a good thing with an evil end or an evil condition valid?

Response to the 1st. Negatively, if the evil end holds itself on the side of the thing vowed, for example, if you vow alms in order to obtain the successful outcome of a theft, or in thanksgiving for robbery. The reason is that the giving of alms for such an end is a blasphemous action, as if God were bringing help for sinning. - But one must answer otherwise, according to the common opinion, if the evil intention only accidentally accompanies the vow, and the evil end, as St. Alphonsus says, holds itself entirely on the side of the one vowing, for example, if someone, vowing for the glory of God, afterward from vain ostentation more willingly vows externally. Cf. St. Alphonsus, n. 206.

Response to the 2nd. Affirmatively, if the vow is made from affection toward the good thing, as it is good, even if joined with an evil cause or condition, as if someone vows alms if he is not caught in theft. For although theft is evil, nevertheless not to be harmed is not evil, but a gift of God; and the vow does not fall upon the evil, but upon the good, insofar as it is good in itself. Much more, however, is this valid if the vow is made from detestation of the evil condition; as if someone vows alms, if and as often as he blasphemes. - Cf. Laymann, lib. 4, tract. 5, chap. 2, n. 7.