Pope Benedict XVI announced Monday that he will step down at the end of this month, the first pope in more than 600 years to vacate the Vatican before his death. He cited the usual health considerations consistent with his age, 85, and said that his post-papal plans would be to live “a life dedicated to prayer.” He will spend some time in a cloistered convent and then, well, who knows? Popes don’t usually retire, so we are not in terribly well-charted territory here.

Another thing that popes usually do not do is write multivolume works about the life of Jesus Christ during their papacies, yet that is what this pope has done with the “Jesus of Nazareth” series. Rather than put out a lot of official encyclicals and other documents, Benedict focused on writing...