Vow (Lat. votum), a voluntary promise made to God, and, as such, carrying with it the most stringent obligation to its fulfilment. Vows, as religious acts connected with the notion of sacrifice, were common to all the religions of antiquity. In Israel they were regarded at times as absolutely irrevocable—the vow of Jephthah is a case in point—but the laws of Leviticus provided for their commutation or redemption by money (Lev. xxvi.). The practice of vows did not cease in apostolic times (Acts, xviii. 18; xxi. 23), and in the later and mediæval church the system received a very extensive development. The Protestant churches, by a reaction against the abuse of monastic vows, discarded the practice altogether. In the Roman Church, however, vows are held to be of divine institution and intimately connected with the most perfect state of the Christian life. A vow is defined by Catholic theologians to be a promise to God de meliori bono—i.e. the matter or object of the vow must be, in moral worth, superior to its opposite. Thus, a vow to marry would be ordinarily null, for the married state is not considered to be in itself better than the unmarried. Vows are mostly concerned with the evangelical counsels as distinguished from the precepts of the Christian law, and with acts of supererogation or of conduct not otherwise obligatory. But a vow to observe a precept gives to it a greater moral value, invests its observance with the character of divine worship, and obtains for it higher merit. Certain important vows, the vow of chastity, of entering a religious order, or making pilgrimage to the Holy Sepulchre, to Compostella, &c., are ‘reserved to the pope’—i.e. cannot be dispensed from except by authority from the holy see. Otherwise the making of simple vows is left to the discretion of the individual, and dispensation from them for a just cause can be obtained from the bishop or religious superior. The church, however, takes under her special charge, or is said in a solemn manner to accept certain vows which on that account are called solemn as distinguished from simple vows. The three solemn vows of poverty, obedience, and chastity, involving complete and irrevocable surrender, essentially constitute the ‘religious’ state. A solemn vow of poverty deprives the subject of all dominion over property. More important is the distinction in reference to the vow of chastity. A simple vow of chastity renders subsequent marriage illicit but not invalid, while a solemn vow nullifies marriage. Yet all monks and nuns do not take solemn vows. In certain newly-instituted communities, and in some countries where the civil legislation interferes with the observance of these vows in their integrity, simple vows are taken. By recent papal decrees simple vows are substituted at least for a period even in the older orders. In the Society of Jesus a certain select number only after many years are admitted to the three solemn vows, and to these vows is then added a fourth, of special obedience to the pope. By a peculiar exception, however, the vow of chastity taken by a Jesuit after his noviciate, though a simple vow in other respects, is made to annul marriage. It should be noted that a priest at his ordination makes no explicit vow of chastity; but the celibacy to which he is bound is treated canonically as a vow, implied in his acceptance of sacred orders. A vow differs from a promissory oath inasmuch as the oath is said to merely call God to witness to the reality or sincerity of the promise at the time it is made. The neglect to fulfil it is commonly thought to contract no greater guilt than what is already involved in the non-fulfilment of the natural promise.
The casuistry of vows is treated in all works of moral theology. But see especially the latest editions of Ferraris, Bibliotheca (art. ‘Votum’).