Clive Staples Lewis's importance as an essayist is identifiable with, and to a great extent owing to, his role as a popular apologist for the Christian faith. His emergence from a successful but nonetheless relatively obscure academic career into the limelight of popular acclaim was the result largely of four series of programs broadcast by the BBC in 1941 and 1942 in which Lewis responded to the invitation of James W. Welch to give "a series of talks on something like 'The Christian Faith As I See It-By A Layman.'" Lewis was a likely candidate for the job: The Pilgrim's Regress (1933), the autobiographical account of his conversion to Christianity, had been noticed earlier by Ashley Sampson of the Centenary Press and Geoffrey Bles Publishers; Sampson subsequently commissioned Lewis to write The Problem of Pain (1940). This book, which addresses in laymen's terms the theological problem of evil and related moral...