The making, keeping, and breaking of promises, oaths, and vows seems to be something close to Taylor Swift’s heart. On the title track of her 2010 album Speak Now, Swift sings of a girl “rudely barging in on a white veil occasion” to deliver a message to the boy that she loves who is about to marry someone else: “Don’t wait or say a single vow; you need to hear me out, and they said ‘speak now.’” Or there is the memorable line in one of her best-loved songs, “All Too Well” (2012): “You call me up again just to break me like a promise, so casually cruel in the name of being honest.” Nearly a decade later, Swift released a ten-minute version of “All Too Well” (2021) with expanded lyrics and an accompanying music video that sparked global gossip about who the subject of Swift’s jilted fury could be. In contrast to her lover’s flippant promise-breaking, Swift expresses her own devotion: “You kept me like a secret, but I kept you like an oath – sacred prayer and we’d swear to remember it – all too well.”

Swift’s lyrics prompt questions that have plagued thinkers down the ages, stretching from Thomas Aquinas to Martin Luther to Giorgio Agamben, from ancient philosophers to the earliest stories in the Hebrew scriptures: What difference does a promise really make? Will something have changed once the love of Swift’s life has said the “single vow” she begs him not to? Is there a connection between an oath and what Swift calls a “sacred prayer”? Many thinkers through history have argued that the invocation of God is an essential aspect of swearing oaths and making vows. While many no longer believe in God, people – not least Taylor Swift – still seem to be drawn to believing in the power of vows, oaths, and promises almost as if there is still a God who listens to the vows we make.

The connection between the divine and the human practice of making promises lies at the heart of the contemporary Italian philosopher Giorgio Agamben’s 2008 book The Sacrament of Language: An Archaeology of the Oath. Agamben notes that “one of the characteristics of the oath on which all the authorities, both ancient and modern, from Cicero to Glotz, from Augustine to Benveniste, seem to be in agreement is the calling of the gods as witnesses.” Among the various accounts of the oath in the history of Western philosophy, Agamben pays specific attention to the Hellenistic Jewish philosopher Philo of Alexandria (ca. 20 BC–ca. AD 50), who in his work Legum allegoriae discusses the oath which God makes to Abraham in Genesis 22:16–17. This oath comes as a dramatic resolution to the scene after Abraham promises God to sacrifice his only son Isaac. Having spared Isaac at the last moment, God provides a ram to be sacrificed in Isaac’s stead and fulfills Abraham’s promise for him. It is shortly after this moment that God makes an oath to Abraham, saying: “By myself I have sworn.”

Commenting on God’s declaration, Philo considers whether it is appropriate to say that God is one who can swear an oath:

Some have said, that it was inappropriate for Him to swear; for an oath is added to assist faith [pisteōs eneka] and only God … is faithful [pistos] … They say indeed that an oath is calling God to witness [martyria] to a point which is disputed; so if it is God that swears, He bears witness to Himself, which is absurd, for he that bears the witness must be a different person from him on whose behalf it is borne.

Contrary to this position, Philo argues that because God is the highest and best of all things, God cannot swear by any other thing – for there is nothing higher or better than God – but only by himself: “God alone therefore is the strongest security first for Himself, and in the next place for his deeds also, so that He naturally swore by Himself when giving assurance as to himself, a thing impossible for anyone but God.”

Philo’s insistence that God cannot swear by anything higher than himself not only anticipates the New Testament teaching in Hebrews 6:13 that “when God made a promise to Abraham, because he had no one greater by whom to swear, he swore by himself,” but also coincides with Jesus Christ’s teaching in Matthew 5:34–35: “Do not swear at all, either by heaven, for it is the throne of God, or by the earth, for it is his footstool, or by Jerusalem, for it is the city of the great King.” The Church Father and Bible translator Jerome (ca. 342–420) comments on Matthew 5:34: “The Savior here has not prohibited swearing by God, but by heaven and earth and Jerusalem.” While Quakers and Anabaptists would later question this interpretation and argue that Jesus unequivocally renounces the swearing of oaths in this passage, what Jerome’s fourth-century interpretation highlights is the transcendent nature of God: for Jerome, as for Jesus’ contemporary Philo, humans should not swear by heaven or by earth or by Jerusalem, because all these things are but creations and possessions of God – his “throne,” his “footstool,” his “city” – which are lower and lesser beings than God. As Hebrews 6:16–17 puts it, “humans swear by someone greater than themselves,” someone whose purpose and faithfulness – and indeed whose promises – are “unchangeable”: namely, God.

This, however, presents a conundrum for Philo: though God is the only fitting assurance for humans to swear by, how can human beings swear by God whose transcendent nature is incomprehensible to them? Writing in the first-century context of Hellenistic Judaism – which, unlike Christianity, did not believe that the divine nature is made known to humanity through Christ’s incarnation – Philo argues that it is improper for human creatures to swear by God, for only God alone has full knowledge of his own nature and essence – something which can never be comprehended by creaturely beings: humans would not know what they are invoking if they swear by God who is ineffable in his divine nature. In his reading of Genesis 22:16, Philo therefore insists that only God can swear by himself: all other creatures do not and cannot swear “by God” but rather “by God’s name.” According to Philo, since finite human creatures do not and cannot grasp the infinite transcendent nature of God, they can only swear by God’s name – the name which has been generously revealed and given to them by God, which allows humans to call upon God in an intimate and personal manner. Philo connects this insight to Moses’ teaching in Deuteronomy:

Naturally no one swears by Him, since he is unable to possess knowledge regarding His nature. No, we may be content if we are able to swear by his name … Moses, too, let us observe, filled with wonder at the transcendency of the Uncreated, says, “And thou shalt swear by His Name” (Deut. 6:13), not “by Him,” for it is enough for the created being that he should be accredited and have witness borne to him by the Divine word. … The very words of God are oaths.

As finite created beings, human beings can only make oaths because God has revealed himself to them in the form of a word (logos) – what Philo calls “the Divine word” – that is his name. Human beings can swear oaths in God’s name only because God has revealed his name to them. In this sense, Taylor Swift is right to draw a connection between oaths and “sacred prayers”: in giving us his name, God made a way for us to address our oaths to him directly, personally, even prayerfully. But what about vows? Is a vow different from an oath? If so, what is God’s involvement with a vow?

Writing some twelve centuries after Philo and Jesus, the medieval Dominican scholastic Thomas Aquinas (1225–74) makes a technical distinction between oaths and vows in his Summa Theologiae:

A vow binds one to God while an oath sometimes binds one to man. … The obligation both of a vow and of an oath arises from something Divine; but in different ways. For the obligation of a vow arises from the fidelity we owe God, which binds us to fulfil our promises to Him. On the other hand, the obligation of an oath arises from the reverence we owe Him which binds us to make true what we promise in His name. (II–II.89.8)

According to Aquinas, where the obligations of vows express our fidelity to God, the obligations of our oaths reflect our reverence toward God. With the increasing popularity and influence of religious orders such as the Franciscans and the Dominicans (founded respectively in 1209 and 1216), the distinction between vows and oaths was quite important, including for Aquinas, who would have made a vow when he joined the Dominican order. To make a vow and dedicate one’s life to God – as those who join religious orders do – is understood as categorically different from the swearing of oaths, which need not necessarily pertain to anything religious. After all, unlike a vow which is a promise made to God, an oath is not a promise one makes to God but merely to fellow human beings.

It was precisely this emphasis on promises made to God through vow-taking which would trouble many of the Reformers just a few centuries later. In 1505, Martin Luther left university, sold all his books, and entered the St. Augustine’s Monastery in Erfurt. As per the practice of his time, Luther would have taken the three monastic vows of obedience, poverty, and chastity upon entering the religious life. However, the monastic vows Luther took did not give him the spiritual life and peace that he wanted. Instead, his attempts to adhere to the promises he made only brought him spiritual distress and existential crises. Less than two decades later, Luther would present fierce theological critiques of the culture and spiritual implications of taking monastic vows in his 1521 work De Votis Monasticis. Luther worried that such promises to God could be seen as binding or forcing one to perform actions or indeed works for God, which would be directly in tension with what he saw as the biblical teaching of justification by faith and not by works. Luther writes:

[God] gave you the freedom in all things and made you free. What else is a vow except your making something obligatory that he declares is a matter of choice. But in granting you this freedom God does not prevent you from putting yourself under obligation or binding yourself to your neighbor, because your neighbor has not, like God, commanded you to be free.

The binding character of a monastic vow as a promise made to God was, in Luther’s eyes, too law-like, as if the vow were a kind of crypto-contract or legal agreement between God and the human vower that compromised the freedom and gift of salvation God freely gives to the human believer through faith. While it may seem that Luther calls us to not “say a single vow” (to invoke Swift’s lyrics), Luther was mainly concerned with monastic and religious vows, as opposed to the marriage vows that Taylor Swift sang of, because for Luther marriage vows (or, perhaps more accurately, marriage oaths) are effectively binding promises made to another person with God as witness, rather than promises made to God.

In his critique of religious vows, Luther sought to emphasize that God’s salvation is a free gift for the Christian believer; in his view, the human fulfillment of their obligations or promises to God is ultimately unattainable. Instead, for Luther, the relationship between God and creature is not the outworking of any human effort or fulfillments of human promises made to God. Rather, it is an outworking of God’s divine promise to his creatures. He writes in De Libertate Christiana (1520):

What is impossible for you, by means of all the works of the commandments, which are many, and which still cannot be of any value, is made simple and easy for you through faith. For God has made all things depend on faith, so that whoever has it shall have all things and be joyful; whoever does not have it shall have nothing. This is what the promises of God provide, what the commandments demand; they fulfill what the commandments demand, so that everything is from God himself, both commandment and fulfillment. He alone commands; he alone also fulfills.

Luther’s famous doctrine of justification by faith is coupled with, or even premised on, an emphasis on God’s fulfillment of his own promise. For Luther, God’s promise is made to us through the preaching of God’s Word – or even God’s divine act of giving us his Word.

Here we find different layers of meaning to God “giving his Word.” On one level, God gives his Word to us as an act of communication or self-revelation (in the preaching of the “Word”). On a second level, God gives us his Word in the sense that his act of self-revelation is – always – an act of making a promise because, as Philo puts it, “the very words of God are oaths”: God’s Word is by definition faithful and trustworthy. On a third (or even trinitarian) level, one that goes beyond Philo’s pre-Christian Hellenistic Judaism, one could say that God gave us his Word and made us a promise by giving us his Son, the one whom John’s Gospel calls his Word: that God promises himself to us in the incarnate person of Jesus Christ. Understood in this distinctively Christian way, the faithful God who gives us his Word and fulfills his promise to us is a trinitarian God, for such a God is in his nature a Word-giving God in the sense that God is one who gives us his Word whom Christians call the second person of the Trinity. The very fact that God is one who faithfully keeps his promise is rooted in his character as a God who is always already – indeed eternally – giving his Word in his trinitarian nature.

From Philo to Aquinas to Luther we find insights not only into the nature of promises, but perhaps also into the nature of the God who reveals himself to his people in promises – or even as promise. God’s nature as promise can be traced – beyond Luther, Aquinas, and even Philo – back to one of the most foundational moments in the Hebrew Bible: namely, God’s self-revelation to Moses in Exodus 3. After the angel of the Lord appears to Moses in a burning bush, God reveals himself to Moses as the “God of your father, the God of Abraham, the God of Isaac, and the God of Jacob” (verse 6), calling to mind the oath God made to Abraham in the past. Honoring and fulfilling the promise he made to Abraham, God announces to Moses that he “has come down to deliver” his people from captivity into a promised land “flowing with milk and honey” (verse 8). God further promises that he will continue to be with Moses as he leads his people into future deliverance: “I will be with you” (verse 12). It is only then, when God’s promises from past, present, and future have been rehearsed and assured that God reveals the Divine name: “I am who I am” or “I will be who I will be” (verse 14).

In the history of Western philosophy, the God who discloses his name as “I am who I am” or “I will be who I will be” in Exodus 3:14 is often understood to be “Being itself”: “I am who I am” or “I will be who I will be” means that God is “Being” par excellence. According to this view, created beings only exist by participating in this God who is “Being itself” (cf. Acts 17:28). However, at the same time, God’s very act of revealing and giving his name to his people can also be understood as an act of establishing some form of relationship with his people: a relationship which God promises to honor and uphold, because God is a faithful God – for “I will be who I will be” is not just a divine name but also a divine promise. Indeed, one might even say, God himself is promise – for God promises himself to his people in the very act of revealing his name to them. According to this reading, God is not simply an abstract philosophical principle of “Being” par excellence, God is “faithfulness” or “promise” par excellence. God is not simply the idle object to whom one makes promises in vows, but also one who makes promises and always keeps them because he is faithful.

Unlike the disloyal human lover in Taylor Swift’s “All Too Well,” who is said to “call [her] up again just to break [her] like a promise,” God is not someone who would ever break his promise. God’s promise to us cannot be broken; it is intrinsically interwoven with our very being: for God called us into being by making a promise (Rom. 4:17). Just as created beings are said to exist by virtue of participating in the God who reveals himself to be “Being itself,” creatures only have their being by virtue of God’s promise to keep his Word and to continue sustaining the existence and integrity of his creation. In other words, to exist is to participate in God’s promise: we only exist and have our creaturely being because God made us a promise and gave us his Word – by speaking the world into existence with and through his Word – through whom “all things came into being” (John 1:3), and in whom “all things hold together” (Col. 1:17). If, as Agamben would have it, “the word of God is, in the words of Philo, an oath,” one can say that it is only because God first gave us his Word and made us a promise that we ourselves can make promises with our vows. Just as we love because God first loved us (1 John 4:19), it is because God first promised us that we can promise ourselves to God in vows. We can make vows and promises only because God first made us a promise, because God is the faithful one who keeps his promise, because God promised himself to us, because God gave us – and continues to give us – his Word.