One of Chesterton’s most frequently quoted jokes was his answer to the question, Which book would you most want to have on a desert island? He said, “Thomas’s Guide to Practical Ship-building”—and there was much of his personality in the remark: wit, of course, but also a rather obtrusively self-complimentary insistence on his own commonsensical attitude toward life.

Msgr. Ronald Knox (1888–1957)—the great man of letters and Catholic convert who became one of the leading apologists of the 20th century— was influenced by Chesterton in many ways, and his approach to the same question was likewise revealing. According to David Rooney’s …