Emeritus Pope Benedict XVI has emerged from his self-imposed silence inside the Vatican walls to publish a letter to a prominent Italian atheist defending his record on sexually abusive priests and discussing topics from evolution to theology to the figure of Jesus Christ.
Excerpts were published by La Repubblica, the same newspaper which two weeks ago published a similar letter from Pope Francis to its own atheist publisher.
The letters indicate that the two men - who live across the Vatican gardens from one another - are pursuing an active campaign to engage non-believers. It is a melding of papacies past and present that has no precedent and signals that the popes - while very different in style, personality and priorities - are of the same mind on certain issues and might even be collaborating on them.
Benedict became the first pope in 600 years to resign when he retired in February, setting the stage for the election of Francis two weeks later. Benedict said at the time that he would spend his final years "hidden from the world," living in a converted monastery tucked behind St. Peter's Basilica, reading and praying.
Benedict's decision to cloister himself was in part due to his own shy, bookish nature, but also to make clear that he was no longer pope and that his successor was in charge.
The resignation immediately raised the not-insignificant question of how the Catholic Church would deal with the novel situation of having one reigning and one retired pope living side-by-side, each of them called "pope," each of them wearing papal white and even sharing the same aide in Monsignor Georg Gaenswein. Fear of schism in the church had prevented popes for centuries from stepping down.
Benedict has been seen only a handful of times since his retirement, and only once with Francis at an official Vatican ceremony in July. A prolific writer, he has published nothing since retiring - except for the encyclical "The Light of Faith" which was signed by Francis but was written almost entirely by Benedict before he resigned.
All of which made Repubblica's publication of his letter to mathematician Piergiorgio Odifreddi all the more remarkable, since it came out of the blue and just two weeks after a letter on almost the exact same subject was penned by Francis on the same pages.
The Vatican spokesman, Federico Lombardi, said it was pure coincidence that the two men had written two Italian atheists on the same subject. Francis' letter uses a language that is much closer to Benedict's style - but Mr Lombardi denied the two had collaborated on it.
In Benedict's letter, he responded to Mr Odifreddi's 2011 book "Dear Pope, I'm Writing You," which in turn was the Italian's response to Benedict's classic "Introduction to Christianity," perhaps his best-known work.