Justification and Sanctification Are Distinct, but Never Separated
At this point, Piper presses Keller with a question that many Christians quietly struggle with: If we are justified by faith alone, how does sanctification fit in? Are both necessary for salvation? And if so, how are they different?
Keller’s response is characteristically pastoral and clarifying.
“You’re really saved by faith, not by how sanctified you are,” he says. “But if you’re not getting sanctified, then you don’t have saving faith.”
This distinction is crucial. Sanctification does not cause salvation, but it reveals it. Keller summarizes it this way: sanctification is the sign of salvation, not the source.
He warns against a subtle but dangerous way many Christians think about the Christian life. Some imagine justification as merely a pardon, after which sanctification becomes a self-powered project. In that framework, forgiveness is God’s job, but growth is ours. Sanctification becomes “what I do to keep God happy with me.”
Keller argues that this mindset quietly undermines the gospel. It turns sanctification into a form of works-righteousness and leaves believers either proud or exhausted.
Why Grace Feels “Scary” at First
One of the most memorable moments in the conversation comes when Keller recounts a discussion with a woman who was beginning to understand salvation by grace alone. Instead of finding the doctrine comforting, she found it frightening.
She explained why. If salvation is based on works, then there is a limit to what God can demand. Like a taxpayer who has paid their dues, a person can say, “I’ve done my part.” But if salvation is truly by grace, then there is no limit to what God can ask. Obedience becomes unconditional.
Rather than leading her toward rebellion, this realization led her toward surrender.
Keller notes that many people assume grace will make obedience optional. But for those who truly grasp it, grace produces the opposite effect. It awakens love, joy, and a desire to give oneself fully to the One who has already given everything.
This is what the apostle Paul means when he speaks of “faith working through love” (Galatians 5:6).
