Objection 1: It would seem that a vow need not be always about a better good. A greater good is one that pertains to supererogation. But vows are not only about matters of supererogation, but also about matters of salvation: thus in Baptism men vow to renounce the devil and his pomps, and to keep the faith, as a gloss observes on Ps. 75:12, "Vow ye, and pay to the Lord your God"; and Jacob vowed ( Gn. 28:21 ) that the Lord should be his God. Now this above all is necessary for salvation. Therefore vows are not only about a better good.
Objection 2: Further, Jephte is included among the saints ( Heb. 11:32 ). Yet he killed his innocent daughter on account of his vow ( Judges 11 ). Since, then, the slaying of an innocent person is not a better good, but is in itself unlawful, it seems that a vow may be made not only about a better good, but also about something unlawful.
Objection 3: Further, things that tend to be harmful to the person, or that are quite useless, do not come under the head of a better good. Yet sometimes vows are made about immoderate vigils or fasts which tend to injure the person: and sometimes vows are about indifferent matters and such as are useful to no purpose. Therefore a vow is not always about a better good.
On the contrary, It is written ( Dt. 23:22 ): "If thou wilt not promise thou shalt be without sin."
I answer that, As stated above (A[1]), a vow is a promise made to God. Now a promise is about something that one does voluntarily for someone else: since it would be not a promise but a threat to say that one would do something against someone. In like manner it would be futile to promise anyone something unacceptable to him. Wherefore, as every sin is against God, and since no work is acceptable to God unless it be virtuous, it follows that nothing unlawful or indifferent, but only some act of virtue, should be the matter of a vow. But as a vow denotes a voluntary promise, while necessity excludes voluntariness, whatever is absolutely necessary, whether to be or not to be, can nowise be the matter of a vow. For it would be foolish to vow that one would die or that one would not fly.
On the other hand, if a thing be necessary. not absolutely but on the supposition of an end---for instance if salvation be unattainable without it---it may be the matter of a vow in so far as it is done voluntarily, but not in so far as there is a necessity for doing it. But that which is not necessary, neither absolutely, nor on the supposition of an end, is altogether voluntary, and therefore is most properly the matter of a vow. And this is said to be a greater good in comparison with that which is universally necessary for salvation. Therefore, properly speaking, a vow is said to be about a better good.
Reply to Objection 1: Renouncing the devil's pomps and keeping the faith of Christ are the matter of baptismal vows, in so far as these things are done voluntarily, although they are necessary for salvation. The same answer applies to Jacob's vow: although it may also be explained that Jacob vowed that he would have the Lord for his God, by giving Him a special form of worship to which he was not bound, for instance by offering tithes and so forth as mentioned further on in the same passage.
Reply to Objection 2: Certain things are good, whatever be their result; such are acts of virtue, and these can be, absolutely speaking, the matter of a vow: some are evil, whatever their result may be; as those things which are sins in themselves, and these can nowise be the matter of a vow: while some, considered in themselves, are good, and as such may be the matter of a vow, yet they may have an evil result, in which case the vow must not be kept. It was thus with the vow of Jephte, who as related in Judg. 11:30 , 31 "made a vow to the Lord, saying: If Thou wilt deliver the children of Ammon into my hands, whosoever shall first come forth out of the doors of my house, and shall meet me when I return in peace . . . the same will I offer a holocaust to the Lord." For this could have an evil result if, as indeed happened, he were to be met by some animal which it would be unlawful to sacrifice, such as an ass or a human being. Hence Jerome says [*Implicitly 1 Contra Jovin.: Comment. in Micheam vi, viii: Comment. in Jerem. vii. The quotation is from Peter Comestor, Hist. Scholast.]: "In vowing he was foolish, through lack of discretion, and in keeping his vow he was wicked." Yet it is premised ( Judges 11:29 ) that "the Spirit of the Lord came upon him," because his faith and devotion, which moved him to make that vow, were from the Holy Ghost; and for this reason he is reckoned among the saints, as also by reason of the victory which he obtained, and because it is probable that he repented of his sinful deed, which nevertheless foreshadowed something good.
Reply to Objection 3: The mortification of one's own body, for instance by vigils and fasting, is not acceptable to God except in so far as it is an act of virtue; and this depends on its being done with due discretion, namely, that concupiscence be curbed without overburdening nature. on this condition such things may be the matter of a vow. Hence the Apostle after saying ( Rom. 12:1 ), "Present your bodies a living sacrifice, holy, pleasing to God," adds, "your reasonable service." Since, however, man is easily mistaken in judging of matters concerning himself, such vows as these are more fittingly kept or disregarded according to the judgment of a superior, yet so that, should a man find that without doubt he is seriously burdened by keeping such a vow, and should he be unable to appeal to his superior, he ought not to keep it. As to vows about vain and useless things they should be ridiculed rather than kept.
Whether all vows are binding?
Objection 1: It would seem that vows are not all binding. For man needs things that are done by another, more than God does, since He has no need for our goods ( Ps. 15:2 ). Now according to the prescription of human laws [*Dig. L. xii, de pollicitat., i] a simple promise made to a man is not binding; and this seems to be prescribed on account of the changeableness of the human will. Much less binding therefore is a simple promise made to God, which we call a vow.
Objection 2: Further, no one is bound to do what is impossible. Now sometimes that which a man has vowed becomes impossible to him, either because it depends on another's decision, as when, for instance, a man vows to enter a monastery, the monks of which refuse to receive him: or on account of some defect arising, for instance when a woman vows virginity, and afterwards is deflowered; or when a man vows to give a sum of money, and afterwards loses it. Therefore a vow is not always binding.
Objection 3: Further, if a man is bound to pay something, he must do so at once. But a man is not bound to pay his vow at once, especially if it be taken under a condition to be fulfilled in the future. Therefore a vow is not always binding.
On the contrary, It is written ( Eccl. 5:3 , 4 ): "Whatsoever thou hast vowed, pay it; and it is much better not to vow, than after a vow not to perform the things promised."
I answer that, For one to be accounted faithful one must keep one's promises. Wherefore, according to Augustine [*Ep. xxxii, 2: De Mendac. xx] faith takes its name "from a man's deed agreeing with his word" [*'Fides . . . fiunt dicta' Cicero gives the same etymology (De Offic. i, 7)]. Now man ought to be faithful to God above all, both on account of God's sovereignty, and on account of the favors he has received from God. Hence man is obliged before all to fulfill the vows he has made to God, since this is part of the fidelity he owes to God. On the other hand, the breaking of a vow is a kind of infidelity. Wherefore Solomon gives the reason why vows should be paid to God, because "an unfaithful . . . promise displeaseth Him" [* Eccles. 5:3 ].
Reply to Objection 1: Honesty demands that a man should keep any promise he makes to another man, and this obligation is based on the natural law. But for a man to be under a civil obligation through a promise he has made, other conditions are requisite. And although God needs not our goods, we are under a very great obligation to Him: so that a vow made to Him is most binding.
Reply to Objection 2: If that which a man has vowed becomes impossible to him through any cause whatsoever, he must do what he can, so that he have at least a will ready to do what he can. Hence if a man has vowed to enter a monastery, he must endeavor to the best of his power to be received there. And if his intention was chiefly to bind himself to enter the religious life, so that, in consequence, he chose this particular form of religious life, or this place, as being most agreeable to him, he is bound, should he be unable to be received there, to enter the religious life elsewhere. But if his principal intention is to bind himself to this particular kind of religious life, or to this particular place, because the one or the other pleases him in some special way, he is not bound to enter another religious house, if they are unwilling to receive him into this particular one. on the other hand, if he be rendered incapable of fulfilling his vow through his own fault, he is bound over and above to do penance for his past fault: thus if a woman has vowed virginity and is afterwards violated, she is bound not only to observe what is in her power, namely, perpetual continency, but also to repent of what she has lost by sinning.
Reply to Objection 3: The obligation of a vow is caused by our own will and intention, wherefore it is written ( Dt. 23:23 ): "That which is once gone out of thy lips, thou shalt observe, and shalt do as thou hast promised to the Lord thy God, and hast spoken with thy own will and with thy own mouth." Wherefore if in taking a vow, it is one's intention and will to bind oneself to fulfil it at once, one is bound to fulfil it immediately. But if one intend to fulfil it at a certain time, or under a certain condition, one is not bound to immediate fulfilment. And yet one ought not to delay longer than one intended to bind oneself, for it is written ( Dt. 23:21 ): "When thou hast made a vow to the Lord thy God thou shalt not delay to pay it: because the Lord thy God will require it; and if thou delay, it shall be imputed to thee for a sin."
Whether it is expedient to take vows?
Objection 1: It would seem that it is not expedient to take vows. It is not expedient to anyone to deprive himself of the good that God has given him. Now one of the greatest goods that God has given man is liberty whereof he seems to be deprived by the necessity implicated in a vow. Therefore it would seem inexpedient for man to take vows.
Objection 2: Further, no one should expose himself to danger. But whoever takes a vow exposes himself to danger, since that which, before taking a vow, he could omit without danger, becomes a source of danger to him if he should not fulfil it after taking the vow. Hence Augustine says (Ep. cxxvii, ad Arment. et Paulin.): "Since thou hast vowed, thou hast bound thyself, thou canst not do otherwise. If thou dost not what thou hast vowed thou wilt not be as thou wouldst have been hadst thou not vowed. For then thou wouldst have been less great, not less good: whereas now if thou breakest faith with God (which God forbid) thou art the more unhappy, as thou wouldst have been happier, hadst thou kept thy vow." Therefore it is not expedient to take vows.
Objection 3: Further, the Apostle says ( 1 Cor. 4:16 ): "Be ye followers of me, as I also am of Christ." But we do not read that either Christ or the Apostles took any vows. Therefore it would seem inexpedient to take vows.
On the contrary, It is written ( Ps. 75:12 ): "Vow ye and pay to the Lord your God."
I answer that, As stated above (AA[1],2), a vow is a promise made to God. Now one makes a promise to a man under one aspect, and to God under another. Because we promise something to a man for his own profit; since it profits him that we should be of service to him, and that we should at first assure him of the future fulfilment of that service: whereas we make promises to God not for His but for our own profit. Hence Augustine says (Ep. cxxvii, ad Arment. et Paulin.): "He is a kind and not a needy exactor, for he does not grow rich on our payments, but makes those who pay Him grow rich in Him." And just as what we give God is useful not to Him but to us, since "what is given Him is added to the giver," as Augustine says (Ep. cxxvii, ad Arment. et Paulin.), so also a promise whereby we vow something to God, does not conduce to His profit, nor does He need to be assured by us, but it conduces to our profit, in so far as by vowing we fix our wills immovably on that which it is expedient to do. Hence it is expedient to take vows.
Reply to Objection 1: Even as one's liberty is not lessened by one being unable to sin, so, too, the necessity resulting from a will firmly fixed to good does not lessen the liberty, as instanced in God and the blessed. Such is the necessity implied by a vow, bearing a certain resemblance to the confirmation of the blessed. Hence, Augustine says (Ep. cxxvii, ad Arment. et Paulin.) that "happy is the necessity that compels us to do the better things."