The Prodigal God: Recovering the Heart of the Christian Faith

Jesus of Nazareth was a first-century Jewish teacher who is the central figure of Christianity: He is the Son in Christianity’s conception of God as a trinity (alongside the Father and the Holy Spirit), and Christianity teaches that his sacrificial death on the cross redeemed humanity, rescuing it from its fallen state. As such, Jesus provides the foundational text and theological core for Keller’s argument. The historical Jesus, who preached and ministered in Galilee and Judea under Roman rule, is the originator of the Parable of the Prodigal Son, recorded in Luke 15. By anchoring his analysis in a story told by Jesus, Keller grounds his book in the authoritative teaching of the Christian faith.

In particular, Jesus’s parable is the primary vehicle for Keller’s typological framework of “younger brothers” and “elder brothers.” In the Bible, Jesus addresses the story to the Pharisees and teachers of the law who criticized him for welcoming “sinners.” Keller uses this context to argue that Jesus’s message was a critique of religious moralism as well as sin in the conventional sense. In Keller’s reading, Jesus presents two equally lost spiritual conditions, challenging the self-righteousness of the religious insiders to whom he speaks.

Keller also presents Jesus as the implicit hero of the story—the “true elder brother” whose presence is conspicuous by its absence in the parable itself. While the elder brother in the story refuses to pay the cost to welcome his sibling, Jesus leaves the Father’s “house” (heaven), pays the cost of his own life on the cross, and secures the restoration of lost humanity. It is this costly grace that makes possible the Father’s “feast,” understood symbolically as humanity and the world’s ultimate restoration to a paradisical state. Jesus’s life, death, and resurrection thus become the answer to the dilemma posed by the two lost sons. His legacy, in Keller’s view, is a new way of relating to God that transcends the dichotomies of religion and irreligion, offering a path to salvation based not on adherence to rules but on divine grace.

Kenneth Bailey (1930-2016) was an American Presbyterian New Testament scholar whose work offers a crucial interpretive lens for Keller’s reading of Luke 15. Having taught for four decades in the Middle East, Bailey brought unique cultural and linguistic expertise to his study of the Gospels. His scholarship, particularly in books like Finding the Lost: Cultural Keys to Luke 15, emphasized understanding the parables through the honor-shame dynamics, social customs, and agricultural realities of first-century Palestinian village life. Keller acknowledges his reliance on Bailey’s work for understanding the parable’s cultural background.

Bailey’s methodology combined deep respect for the biblical text with insights from ethnography and early Syriac and Arabic Christian commentaries. This approach allowed him to illuminate nuances in Jesus’s stories that are often lost on modern Western readers. He demonstrated that Jesus’s parables were deeply embedded in a specific social context, crafted to be heard and understood by a particular audience, however universal their underlying messages might be. In this, Bailey’s approach aligns with Keller’s argument that a surface-level reading of the story misses its subversive nature.

Bailey’s specific contributions to understanding the prodigal son narrative are foundational to Keller’s exegesis. It is Bailey who explains the nature of the younger son’s request for his inheritance (bios, or “life”), which was tantamount to wishing his father dead. He also clarifies the immense social cost to the father, who would have had to liquidate ancestral land, and the way he “lowers” himself in running to greet his son. These insights allow Keller to emphasize the “prodigal,” or extravagant, nature of the father’s love and grace. Bailey’s cultural analysis thus supports Keller’s central theological claims about the costliness of grace.

Through his writings, Bailey helped normalize a culturally specific approach to biblical interpretation among pastors and lay readers, influencing a generation of preachers, including Keller. His legacy lies in his ability to bridge the gap between ancient text and modern reader, uncovering the original power of Jesus’s teachings.

Edmund P. Clowney (1917-2005) was an American Reformed theologian and influential president of Westminster Theological Seminary. As a leading proponent of redemptive-historical, Christ-centered preaching, Clowney taught that every biblical text should be understood and preached in relation to the person and work of Jesus Christ. This interpretive framework, outlined in works like Preaching Christ in All of Scripture, became a hallmark of Keller’s ministry and writing.

Clowney’s direct influence on The Prodigal God is both methodological and personal. Keller’s entire approach to the parable—reading it not just as a story about the father’s forgiveness but as a story that points to the necessity of a “true elder brother,” Jesus—is a direct application of Clowney’s analytical lens. Keller explicitly credits Clowney’s sermon “Sharing the Father’s Welcome” as the catalyst for the book’s central ideas, stating that it “changed the way [Keller] understood Christianity” (xv). This positions Clowney as the key mentor whose insights provide the book’s theological template.

Martin Luther (1483-1546), the German theologian who ignited the Protestant Reformation, implicitly provides much of the doctrinal foundation for Keller’s critique of religious moralism. Luther’s recovery of the doctrine of justification by faith alone (sola fide) is the historical and theological backdrop for Keller’s argument against any form of self-salvation. When Keller defines the elder brother’s sin as using his moral record to control God, he is echoing Luther’s polemic against the works-righteousness he perceived in the medieval Catholic Church.

The core Lutheran distinction between law and gospel undergirds Keller’s analysis. The elder brother represents a life lived under the law—a performance-based system of earning God’s favor. The welcome offered by the father represents the gospel—a system of free, unmerited grace. By applying this paradigm to both the religious and the irreligious, Keller extends Luther’s critique to modern secularism, arguing that both are ultimately attempts to justify oneself apart from Christ. Luther’s theology provides Keller with the language to frame repentance as a turning from self-trust to God’s grace.

Beyond supplying much of the text’s framework, Luther’s teachings also buttress Keller’s particular claims. He notes, for instance, that despite emphasizing faith alone as necessary for salvation, Luther stressed that real Christian faith necessarily manifests in works. For Keller, the popular misconception of figures like Luther echoes the popular misconception of Christianity itself—a misconception rooted in the tendency to “default” to dry religion, a problem Luther similarly diagnosed.

Dietrich Bonhoeffer (1906-1945) was a German Lutheran pastor and theologian whose resistance to the Nazi regime led to his martyrdom. His thought, forged in the crucible of the Confessing Church’s struggle against state co-option, lends moral and theological weight to Keller’s argument about the nature of grace. Keller draws specifically on Bonhoeffer’s distinction between “cheap grace” and “costly grace” from his classic work, The Cost of Discipleship.

Bonhoeffer’s concept of “cheap grace” as forgiveness without repentance or discipleship helps Keller preempt a potential misreading of his own message. To avoid the impression that the father’s welcome is a license to behave however one chooses, Keller invokes Bonhoeffer’s insistence that true grace is transformative. He explains that grace is free, but it was not cheap; it cost God the life of his Son. Once properly understood, this “costly grace” elicits a response of grateful obedience from the believer. Bonhoeffer’s legacy provides a historical and ethical anchor for Keller’s call to a discipleship that is both grace-filled and demanding.