The Life of Virtue - Vows and Oaths

Modern English usage seems to have lost the distinction between a ‘vow’ and an ‘oath’. Often these words are used interchangeably. This blurring of the two terms is unfortunate, as when the words are used properly, they express two different dynamics of our relationship with God.

A vow is a promise, a special type of promise that is made to God. This promise to God differs from our earthly promises. When we make promises to other people, it is to the benefit of the person to whom we make the promise. When we make a promise to God; it is of no benefit to God but to us. As St. Augustine says, What is given to Him is given to the giver. When we make a vow we fix our will on what is fitting to do, namely the worship and service of God.

An oath is calling God to witness a proposition that cannot be confirmed by necessary reason. With an oath, unlike a vow, we take from God rather than give to Him. We take His testimony and witness. We can be confident that these are true because He is Truth: He cannot lie nor is anything hidden from Him. When we swear an oath by God, we acknowledge His unfailing truth and omniscience: we express our faith in Him. It is therefore a grave sin to use an oath frivolously. By doing so we show irreverence to God.

Whilst it would seem that swearing oaths is an act of reverence to God, many object to it on account of the words of Our Lord in the Gospel of Matthew: but I say to you not to swear at all, neither by heaven, for it is the throne of God, nor by the earth, for it is his footstool, nor by Jerusalem, for it is the city of the great king (Matt 5:34-35). Jesus does not, however, forbid us from swearing 'by God' but 'by creation'. When we do this we raise what is creaturely to the level of the divine. When we swear by creation we are actually cursing what we call to witness. However we may swear by certain creatures that reflect the Divine Truth of God, such as Mary, the Saints, and the Gospel. Here we are not swearing by the creatures themselves but by their reflection of Divine Truth.

The Catechism of the Catholic Church says that, following St Paul (2 Corinthians 1:23; Galatians 1:20), the tradition of the Church has understood Jesus' words as not excluding oaths made for grave and right reasons. The holiness of the divine name demands that we not use it for trivial matters (see CCC §§2153-55).