‘The lecturer, a short, thickset man with a ruddy face and a big voice, was coming to the end of his talk.” That was the opening sentence of theTimemagazine cover story for September 8, 1947. The subject of the story, who swiftly exited the classroom for the nearest pub, was the Oxford University don and best-selling author Clive Staples Lewis. How did a scholar of medieval literature, with no formal theological training — a strident atheist in his youth — become, in the words ofTime, “one of the most influential spokesmen for Christianity in the English-speaking world”?