A new book about celibacy and the Catholic Church has set off a firestorm at the Vatican as Pope Francis contemplates rule changes for married priests in remote areas like the Amazon. The book is co-authored by retired Pope Benedict.

To have two men at the Vatican dressed in white is rare. Benedict XVI is just the second pope to resign in the church's 2,000 year history.



Pope Emeritus Benedict pledged not to interfere on major church affairs to leave room for his successor, Pope Francis, to lead. So when the former pope was cited as co-author of "From the Depths of Our Hearts: Priesthood, Celibacy, and the Crisis of the Catholic Church," Benedict was seen as putting a very influential papal thumb on the scales.

Benedict argued for the "necessity of celibacy," writing, "Serving the lord … requires the total gift of a man."



Francis, who also supports priestly celibacy, is contemplating a rule change recommended by bishops allowing the ordination of older, married men in remote regions of the Amazon where there's a priest shortage.

"Of course, everybody knew that a retired pope in the church always is a difficult situation," Monsignor Karel Kasteel, who served seven popes, told CBS News correspondent Seth Doane.

On key church issues, Benedict and Francis are generally aligned, Kasteel said.

Asked if Benedict is breaking his vow to be quiet after retiring, Kasteel said, "He vowed to be obedient to his successor. I never heard that he would shut up forever."



Benedict's personal secretary, Archbishop Georg Gänswein, reached out to the main author of the book, Cardinal Robert Sarah, asking him to remove Benedict as co-author, calling it a "misunderstanding" and adding, in a statement, that Benedict had not authorized a joint-authorship.



But Sarah stands by his version of events, tweeting personal correspondence with the pope emeritus, who, on his letterhead, wrote to the cardinal, "Finally I am able to send you my thoughts on the priesthood … I leave it to you if you find some usefulness." Then the retired pope wrote, "the text can be published."



"The Holy Father likes people to say what they have to say," Kasteel said.

Pressed on if Francis likes when other popes say what they have to say, Kasteel said, "Well, that's a question you'd have to ask the Holy Father himself."



The publisher of the book plans to release it as co-authored.