§ II. On The Matter Of A Vow

382. Principles. - I. The matter of a vow must be a morally good thing, because God is not worshiped by an action indifferent from every side; indeed it must be concerning a better good, that is, better than its opposite; otherwise it would impede a greater good, which cannot be pleasing to God. But a better good is understood not only absolutely in itself, but also relatively to circumstances; and thus the vow of entering matrimony which someone emits because of experienced fragility is valid, although celibacy in itself is better.

II. The matter of a vow ought to be a morally possible thing; because a vow is a promise made to God with the intention of obligating oneself. But no one can obligate himself to something morally impossible for himself. But if the matter is divisible and in part possible, as a sum of money, for this part the vow is valid; but it is not valid if it is morally indivisible, as the parts of a church; or if it is indeed divisible, but it is established that the one vowing willed to obligate himself to each part by way of one thing, and had each indivisibly before his eyes. Thus commonly.¹

383. Questions. - Quaer. 1° Is a vow concerning matter already prescribed from elsewhere valid?

Resp. Affirmatively; first, because it is not repugnant for a debtor to be obligated by diverse titles; then also the vow of this sort concerns a thing good in itself, since it is supposed to have been prescribed; and finally it concerns a better good, since the new bond can contribute to greater fidelity and devotion in fulfilling the law. - Thus commonly.²

Quaer. 2° Is a vow of a good thing with an evil end, or an evil condition, valid?

Resp. to the first. Negatively, if the evil end, although only impulsive, provided the vow would not be made without it,³ holds itself on the part of the thing vowed; for example, if you vow alms to obtain a happy success of 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 furnished help for sinning. Otherwise it must be said, according to the common opinion, if the evil intention only accidentally accompanies the vow, and the depraved end, as St. Alphonsus says, holds itself wholly on the part of the one vowing, for example if someone, vowing for the glory of God, afterward more gladly vows externally from vain ostentation.⁴

Resp. to the second. Affirmatively, if the vow is made from affection toward the good thing, as it is good, although joined with an evil cause or condition, as if someone vows alms if he is not caught in theft. For although the theft is evil, nevertheless not to be injured 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. But much more does this hold if the vow is made from detestation of the evil condition, as if someone vows alms if and as often as he blasphemes. - Laymann.¹

Quaer. 3° Is a vow of not sinning valid?

Resp. 1° A vow of avoiding all sins, even the slightest, is not valid, because this is impossible.²

Resp. 2° But a vow of avoiding all mortal sins, or all fully deliberate venial sins, is valid, because this is possible with divine grace and without a special privilege, and persons who love perfection avoid them sufficiently. Likewise a vow of not committing venial sins of a certain kind is commonly valid, for example never lying, especially in persons of great virtue; but in others of moderate virtue it will be impossible matter; indeed in some matters, for example of dishonest thoughts, as to any and even the slightest subreption, of idle thoughts, etc., since they are inevitable as to all, the vow is null.³