(b) As to External Performance.—If a vow is personal, one must perform it personally, for one’s own act was promised, and hence, if personal performance becomes impossible, it is not necessary or valid to use a proxy; if a vow is real, one may use goods given by others, but one is not obliged in case of poverty to seek the goods of another, since one’s own goods were promised.
2217. The Obligation of Certain Kinds of Vows.—(a) Conditional Vow.—The vower is not obliged by the vow unless the condition is fulfilled, and this is probably true even when the condition is equivalently, but not formally, fulfilled (e.g., Titus, who has to support his mother, vows to enter religion as soon as she contracts marriage, but the mother unexpectedly dies and Titus is thus freed of her support). The vower is not guilty of sin against the vow if he prevents the fulfillment of the condition, unless he uses unlawful means. Such means are not employed if one is not obliged to fulfill the condition (e.g., a vow to pay an alms of $10 if one gets drunk), or if non-fulfillment is due to weakness, not to the purpose to defeat the vow (e.g., a vow to pay an alms of $100, if one remains sober for a year, when the vower becomes intoxicated accidentally or through frailty before the year is up), or if non-fulfillment is due to the exercise of one’s right (e.g., a vow to enter religion if one’s parents consent, when the vower in lawful ways persuades his parents not to consent). The vower is guilty of sin against the vow, if he uses unlawful means to prevent the condition’s fulfillment (e.g., if he gets drunk purposely in order to evade the alms promised for sobriety, or if he uses fraud or force to keep his parents from consenting to a vow which he has made dependent on their consent).
(b) Penal Vow.—The vower is not obliged by the vow if the act against which the vow is made is committed by him but is not sinful (e.g., Claudius vowed not to play cards, but on a certain occasion did play after having received a dispensation), or is only materially sinful (e.g., Balbus vowed not to use profane language, but on a certain occasion did use such language inadvertently), or is not sinful against the vow, at least if the penalty is for violation of the vow (e.g., Caius vowed not to quarrel under penalty of an alms for breaking the promise, but on a certain occasion did quarrel, adverting to the sin against charity, but not to the vow), or is venially sinful on account of the imperfection of the act, at least if the penalty is grave. If the vower has not determined the number of times the penalty is to be paid, it seems that it should be paid only after the first fault, if the penalty is grave and one that is not customarily repeated (e.g., a distant pilgrimage, a large alms), but should be repeated after every fault if the penalty is slight and one that is customarily repeated (e.g., a decade of the Rosary, a small alms).
(c) Disjunctive Vow.—The vow is null if one of the objects to be chosen from is evil, vain or impossible (e.g., a vow either to earn or to steal the money for an alms). The vower is held to nothing if before his choice one of the things to be chosen from has become impossible (e.g., Claudius vows to give one or the other of two chalices he owns, but before he makes his choice one of the chalices is stolen), or if after his choice the thing chosen becomes impossible (e.g., Claudius decided to give the larger of two chalices, but before he could give it, it was stolen). The vower is held, however, if one of the things to be chosen from has become impossible before choice through the vower’s own fault (e.g., Claudius’ chalice was stolen before his choice because he had culpably delayed to make a choice), or if the thing not chosen has become impossible after the choice (e.g., Claudius decided to give the large chalice and the small one was stolen afterwards).
(d) Doubtful Vow.—Doubts about the essentials, that is, whether a vow was really made (e.g., whether it was a vow or only a resolution, whether there was the requisite intention or deliberation, whether the vow was invalid on account of fear, etc.), or whether a vow certainly made was fulfilled, must be settled according to the principles for directing a doubtful conscience (see 672 sqq.). Thus, if it is more probable that a vow was made or that a vow was not fulfilled, the decision must be for obligation according to the Probabiliorists; but if there remains a positive doubt whether only a resolution was made, or whether a vow was fulfilled, there is no obligation according to the Probabilists. Doubts about accidentals, that is, whether a vow was of this kind or that (e.g., the circumstances of quality, quantity, number, etc.), must be settled according to reasonable rules of interpretation of the mind of the vower.
2218. General Rules of Interpretation of Doubtful Vows.—(a) Private vows must be interpreted according to the expressed or presumptive intention of the vower, for a vow is a private law, and the vower the lawmaker. (b) Public vows must be interpreted according to the sound doctrine of approved authorities on theology and Canon Law.
2219. Special Rules for Interpreting the Mind of the Vower.—(a) A doubtful vow should be interpreted from internal evidence, that is, from the language of the vow itself and the significance usually attached to the terms used, for the presumption is that the vower meant to express himself in the ordinary speech used for vows. Thus, a vow of “virginity” usually means the same as a vow of “chastity,” and should be so understood unless there is reason for a stricter interpretation. The language of a vow is to be understood in the light of the purpose of the vower (e.g., a vow to give a chalice to a church does not mean a glass chalice, since the Church employs only chalices of precious metal); a vow to hear Mass daily does not mean that one must hear two Masses on Sunday, since the purpose of the vow is to let no day pass without assistance at Mass.
(b) A doubtful vow that cannot be sufficiently construed from internal evidence should be judged from general presumptions, that is, from the custom as regards the vow taken (e.g., one who vows an alms is understood to promise the amount that others in his condition promise), from the custom or law as regards the matter of the vow (e.g., one who vows a perpetual fast is understood to promise a fast on days other than Sundays and holydays, for the church law distinguishes between fast days and feast days), from the rules governing the interpretation of laws (e.g., since things odious are to be of strict interpretation, he who vows to give something may himself determine what he wishes to give, provided it is not ridiculously small), from the conditions that are implied in every vow as to possibility, the rights of others, change in circumstances, etc. (e.g., he who promises to become a religious means that he will do so, if a Religious Order will accept and keep him; he who promises a gift means that he will give without prejudice to the claims of third parties, etc.).
2220. The Advantages of Vows to the Vowers.—(a) A first advantage is that a vow strengthens the will of the vower to do good and avoid evil. This is an important advantage, since human nature is so weak and inconstant and so much in need of helps that will add resolution and perseverance to its efforts. The vow is a promise binding not only in honor but also as a religious duty, and an act that has a special claim on divine assistance and a favorable answer, and hence it is a powerful ally to a virtuous life. True, he who takes a vow is subject to greater sin if he is unfaithful. But there is no good that has not some risk attached to it, and the risk here is due, not to the vow itself, but to the weakness of the will which may use it improperly. The person who thinks only of the dangers of storms will neither sow nor reap (Eccles., xi. 4).
(b) A second advantage is that a vow makes the good done more meritorious and praiseworthy. It adds to the virtue practised (e.g., abstinence) the virtue that directs (viz, divine worship or religion, the most excellent among the moral virtues); it offers God a more perfect subjection, since it presents to Him, not only a single act here and now, but the power itself of the will to do the opposite; it acts from a greater resolution and firmness, a circumstance that gives perfection to virtue. All this should be understood _per se_, or with the qualification “other things being equal”; for if we suppose that a person who has no vow serves God with great charity and fervor, there is no doubt that he is better before God than one who has vows and performs them carelessly and reluctantly.