Article II: On the Matter of Vow

S. Th. II-II, q. 88, a. 2.

716. Conditions required on the part of the matter for the validity of a vow. - By the matter of a vow we understand the action itself which is promised to God. If it is a mere action or omission of the one vowing, for example, a pilgrimage, fasting, the vow will be personal; but if the operation is concerned with an exterior thing, as almsgiving with money, the vow is real, in which case the proximate matter will be the action, but the thing the remote matter; but if a mere action is promised and at the same time an operation concerning an exterior thing, the vow is mixed (can. 1308, § 4).

Moreover, on the part of the matter three conditions are also required for the validity of a vow: for the promised action must be morally good, better than its opposite, and possible (can. 1307, § 1).

717. The matter of a vow must be morally good. - For it would be vain to promise to someone what would not be acceptable to him; but a work acceptable to God exists only if it is virtuous; therefore a vow can be made concerning nothing illicit, nor concerning anything indifferent, but only concerning a virtuous act. Hence:

1. A vow concerning an evil act is invalid, whether it is prohibited by the law of nature or by positive law, unless in this latter the exception of a vow is understood; whether it is evil from the object, or from the end or circumstance, which hold themselves on the part of the promised work and therefore fall under the vow: for these affect the very matter of the vow, that is, the promised work, and render it evil.

Thus a vow is not valid concerning alms to be given solely for seducing a girl or for committing theft, for acquiring victory in a duel, for obtaining vain glory by it, in thanksgiving for theft committed, or concerning the sacrifice of Mass to be performed on Good Friday, etc. - On the contrary, if a circumstance or evil end holds itself on the part of the one vowing and therefore does not fall under the vow, these do not render the very matter of the vow or the promised work evil, but only the act of vowing, for example, if the evil end is only secondary and an impulsive cause of the vow, or an evil circumstance is added to the vow, or the vow is emitted on the occasion or under the condition of some evil.¹ Examples are: a vow formed from ambition, the vow of one who is prohibited from vowing, a vow emitted before several persons so that vain glory may be obtained from hearing of the vow, a vow of giving alms if I escape healthy from the duel, a penal vow.

¹ And so an evil circumstance on the part of the promised work, because it affects the matter of the vow, renders the vow invalid; an evil circumstance on the part of the one vowing alone or of the promise renders the vow only illicit, because it does not affect the very matter of the vow.

2. A vow concerning a licit work incompatible with the fulfillment of a precept is invalid.

Thus a vow concerning a pilgrimage to be undertaken while Mass of precept is to be heard.

3. A vow concerning an indifferent work is invalid, except insofar as it is employed for a good end, not indeed from the mere intention of the one vowing, but from itself as a proportionate means for better attaining that end: for by this reason it is good by the goodness of the end.

Thus, for example, a vow not to approach a house which is an occasion of sin for someone is valid. But eating, drinking, walking, not mounting a horse, passing through such a street, playing, are not matter of a vow; but in these things to avoid excess is matter of a vow.

718. The matter of a vow must be better than its opposite. - For it is not pleasing to God that someone oblige himself to omitting what is more pleasing and acceptable to Him, "nor does it pertain to reverence for God that a less good work be done, while its better opposite is omitted." The better good is:

a) a work of counsel, which by excellence is better than its contrary and is maximally voluntary or in the power of the one vowing, and therefore is most properly the matter of a vow, principal and spontaneous;

b) a work of precept, which is also better than its contrary, at least insofar as it is prescribed: for nothing prevents someone from adding the voluntary bond of a vow to the necessary bond of a precept;

c) indeed even a work which is not in itself, but in these circumstances for the one vowing, better than its contradictory, that is, than its omission.

Hence per se and generally a vow is invalid concerning a good which is impeditive of a greater good, for example, not to undertake the clerical or religious state, to marry, to practice trade, to go into the military, etc.; nevertheless some good which per se and absolutely is lesser can per accidens and relatively become a greater good, and then the vow is valid, for example, if someone sees that the reception of orders would become harmful to himself, or if someone vows marriage for repairing scandal, or fulfilling a promise, or on account of the honor of a girl, or for legitimizing offspring, or on account of great fragility as a remedy of concupiscence, or on account of the common good. Nor is a vow not to vow valid, but a vow not to vow without the permission of the confessor is valid; in which case, if nevertheless someone vows without consulting the confessor, he does this illicitly indeed but validly, unless he intended the vows to follow not to be valid, and had not retracted this prior will. Nor is an unlimited vow not to petition dispensation from vows valid; nor a vow of obeying the confessor in all things in such a way that confession could not licitly be made with any other.

719. The matter of a vow must be possible, or in the power of the one vowing. - For the impossible cannot be efficaciously intended, and no one is bound to it, nor can he oblige himself to it. Hence a vow is invalid:

1. concerning a necessary thing, for example, a vow of dying, of not flying, etc.;

2. concerning another's thing insofar as it is not in our power, for example, a father vowing his son to a religious order. Namely, concerning the deed of another it is not valid, except insofar as it is in the power of the one vowing and he promises that he will take care, as much as he can, that the work be placed by the other;

3. concerning a thing physically or morally impossible; hence a vow of avoiding all venial sins, even the very slightest, collectively, or of never sinning venially, is invalid.

But a vow of avoiding all mortal sins is valid; likewise a vow of avoiding fully deliberate venial sins, or a certain species of venial sins, or of always choosing that which seems more perfect, unless it is a question of persons of modest virtue, or of matter which absolutely no one can avoid, for example, indecent, idle thoughts, etc.

720. A vow whose matter is only partly honorable, better, or possible, if one intended the parts undividedly after the manner of one thing, as in a disjunctive vow, is wholly null; - but if dividedly after the manner of several things, so that the vow is equivalent to several and is virtually multiple, or if someone wished to oblige himself as much as he can, he is bound to the possible part. But if he explicitly intended nothing, he is judged to have vowed according to the nature of the thing and common estimation: when the parts of the thing promised cannot or are not accustomed to be separated, the vow ceases, for example, a vow of celebrating Mass, of building a church, of undertaking a pilgrimage, etc.; but when they can and are accustomed to be separated, it obliges to the part, for example, a vow of fasting the whole week, of giving 100 francs; or also if the principal part is possible and the accessory impossible, it obliges to the possible part, otherwise conversely, for example, a Roman pilgrimage with fasting or a hair-shirt (a. 3, ad 2).

One vowing to avoid all venial sins is bound to nothing, unless he intended to oblige himself as much as he can; a spouse vowing chastity is bound not to ask the conjugal debt.

One who has emitted several incompatible vows ought to keep the more worthy; if such is not present, the earlier is to be preferred to the later.

721. How great a sin it is to vow invalid matter. - These principles are valid: 1. To vow a mortally evil thing is a grave sin.

2. To vow a lightly evil thing, even per se, seems a grave sin: for it is a great direct irreverence toward the most holy God, to will that He have even the slightest evil as acceptable; but per accidens, on account of ignorance or inadvertence, it is often venial.

3. To vow an indifferent thing or a lesser good is only venial.

4. No one seriously vows an impossible thing, except from ignorance, which can be lightly culpable; to do this from jest and levity is venial.