“Improvisation.” We think of jazz—some bebop master following his horn in the genius of the moment. Or theater—an actor striking that authentic note by responding, on the spot, to the lines that came before his. But what does improvisation have to do with ethics. Samuel Wells defines improvisation in the theater as “a practice through which actors seek to develop trust in themselves and one another in order that they may conduct unscripted dramas without fear.” Wells suggests that such a definition is highly appropriate to Christian ethics. He establishes theatrical improvisation as a model for Christian ethics, a matter of “faithfully improvising on the Christian tradition.” The Bible is not so much a script to rehearse as it is a “training school” that shapes the habits and practices of a community in action. Drawing on Scriptural narratives and church history, he details six practices that characterize both improvisation and Christian ethics—including categories such as “forming habits”, “questioning givens,” and “reincorporating the lost.” He concludes with specific examples of ethical issues, such as facing evil and the perils and promises of genetically-modified food. Wells’s fresh and imaginative discussion reinforces the goal of Christian ethics—not to “help someone act Christianly in a crisis” but to teach Christians to “embody their faith in the practices of discipleship all the time.”