The Prodigal God: Recovering the Heart of the Christian Faith

Timothy Keller’s The Prodigal God invokes the Protestant Reformation’s core debate over the nature of salvation by recasting it through what Keller terms the Parable of the Two Lost Sons. Where the Catholic Church had stressed the necessity of both faith and Christian living, leaders of the Reformation, most notably Martin Luther, promoted the doctrine of sola fide (faith alone). This asserted that divine acceptance is a gift of grace, God’s unconditional love and mercy, not a reward for moral works. Yet this doctrine has always faced the charge of encouraging moral license, a danger theologian Dietrich Bonhoeffer termed “cheap grace.” As Bonhoeffer wrote, “Cheap grace is the deadly enemy of our Church. We are fighting to-day for costly grace” (Bonhoeffer, Dietrich. The Cost of Discipleship. Touchstone / Simon & Schuster, 1995).

Keller was a Presbyterian, a branch of Protestant Christianity that arose in 16th-century Scotland and England, premised largely on Calvinism as interpreted by Scottish theologian John Knox. As such, The Prodigal God holds to the basic doctrine of sola fide; Keller argues that the elder brother’s apparent goodness is a form of lostness because its motive is leverage, not love; for him, “Careful obedience to God’s law […] serve[s] as a strategy for rebelling against God” (43). However, Keller also echoes Calvin’s own contention that good works flowed from faith. In The Institutes of the Christian Religion, for example, Calvin writes, “If that righteousness of works, whatever it be, depends on faith and free justification, and is produced by it, it ought to be included under it and, so to speak, made subordinate to it, as the effect to its cause” (Calvin, John. The Institutes of the Christian Religion. Translated by Henry Beveridge, Christian Classics Ethereal Library, 1599). Likewise, Keller argues that someone who has fully grasped the Christian message will do good works (in the sense of following God’s law) because they will want to, not because they have to: “The key difference between a Pharisee and a believer in Jesus is inner-heart motivation. Pharisees are being good but out of a fear-fueled need to control God. […] Christians have seen something that has transformed their hearts toward God so they can finally love and rest in the Father” (96). Moreover, Keller argues that that “something” is the fact that grace is free to the recipient but infinitely costly to the giver, Christ. Keller’s gospel framework thus upholds salvation by grace while demanding a response that is anything but cheap.