Good writers have many techniques. They know when to surprise their readers, when to confront their readers, and when to move their readers—all to make their readers think.
In Galatians 4, Paul desires to demonstrate that life by the Spirit is superior to enslavement to the flesh. So, he uses an advanced rhetorical technique. A brilliant writer, who had been trained in the most prestigious of classrooms, Paul invites his first-century readers to explore the differences between these two ways of living through allegory.
Allegory is a literary device that enables writers to use a story, poem, or word picture to make a broader point. Allegory relies on connections or associations. Writers who use allegory trust that their readers will understand that the story being told actually has a deeper meaning. They hope their readers will realize that the drama unfolding on the page actually articulates a broader truth.
Allegory sounds complex when you try to define it. But perhaps this example will make it easier to understand:
Think of C.S. Lewis’ The Chronicles of Narnia. A casual reader could argue that Lewis simply tells the story of a mystical world that was rescued by a talking lion. But those who are familiar with Lewis’ deep Christian faith, and those who are familiar with the story of the Bible, are able to recognize the connections and associations between Lewis’ fantasy world and the story of Scripture. They recognize that Narnia isn’t merely about kings and queens and spells and animals. They see that Aslan portrays Jesus, even as Edmund represents Judas.
In the same way, in Galatians 4:23-31, Paul uses a story that his readers know well to help them understand a concept that remains difficult for them to grasp. Paul uses the story of Abraham and his two wives—Sarah and Hagar—to convince his readers that life defined by adherence to Old Testament law is not superior to the life that Christ offers through faith.
To understand the point that Paul is trying to make, it’s important that we remind ourselves of the story of Abraham, Sarah, and Hagar.
Beginning in Genesis 11, we read that God called Abraham to marry Sarah and then promised Abraham that he would become the father of a great nation, through which all the world would be blessed. Abraham trusts God’s promise. But after some time passes, Abraham and Sarah remain childless. It seems as if God’s promise is in jeopardy.
So, Sarah concocts a plan. She suggests Abraham sleep with her slave, Hagar, saying “it may be that I shall obtain children by her.” Abraham consents to the plan, and soon Hagar bears a son named Ishmael.
However, when Abraham reaches his 99th birthday, God comes to Abraham and reaffirms His promise, declaring that Sarah will indeed bear Abraham a son. The elderly couple finds this news hard to believe. But in Genesis 21, it happens. Sarah gives birth to Isaac. God’s promise is fulfilled.
This story would have been familiar to Paul’s first-century readers. In the same way that we know Dorothy traveled to Oz or that Simba reclaimed Pride Rock from his evil uncle, Paul’s first-century readers in Galatia would have been well aware of the contours of Abraham’s story.
This is why Paul uses it as an allegory in Galatians 4.
He wants his readers to associate the benefits of life by the Spirit according to God’s promise with Sarah, and the deficiencies of life according to the flesh with Hagar.
And so he writes, “Abraham had two sons, one by the slave woman and the other by the free. His son by the slave woman was born according the flesh, but his son by the free woman was the result of a divine promise” (Gal 4:22-23).
Paul makes clear “these things are being taken figuratively” (Gal 4:24). He wants his readers to recognize that these two women and their sons are being used allegorically in his argument to represent the differences between God’s covenant with Moses on Mount Sinai (i.e., the covenant by which God’s people had to maintain the entirety of the Old Testament law) and the covenant made by God to Abraham (i.e., the covenant in which God promises Abraham that He will unilaterally act on Abraham’s behalf, blessing Him immensely and using him, in turn, to bless others).
Paul invites his audience to consider which way of life is better: Trusting in your own ability to keep a law that’s impossibly perfect? Or trusting a promise-keeping God, who did what He said He would do for Abraham?
Paul’s hope is that his readers will see that, like Isaac, they are children of God’s promise. They have been made part of God’s family through God’s unilateral work on their behalf. They no longer need to live as if they are slaves to rules and regulations that suggest they might earn God’s favor. They simply need to trust what God has done for them by faith.
Paul’s allegory in Galatians 4 has captured the attention of scholars and theologians for centuries. Much as been written about the contours and complexities of Paul’s writing in this chapter. Numerous articles and sermons exploring the topic are available online. In my opinion, however, no one explains this passage with more clarity than Charles Spurgeon, the renowned 19th-century Baptist preacher. If you’d like to read his comments on the text, click here.
 It is worth noting, however, that Lewis maintained his Narnia stories weren’t allegories but “supposals.” For Lewis, a story was only allegorical so long as its tangible characters represented an intangible idea. (The English professor had quite concrete definitions for literary devices.) Indeed, Lewis maintained that a character can allegorically represent sacrificial love as a concept, but a character cannot allegorically represent Jesus Christ (a real person). For more, see “Why Narnia Isn’t Allegorical.”