But Benedict has tried to address those worries over the past two weeks, saying that once retired he would be "hidden from the world" and living a life of prayer.
In his final speech in St. Peter's Square on Wednesday, he said he wasn't returning to private life exactly, but rather to a new form of service to the church through prayer.
And on Thursday he went even further with his own public pledge of obedience to the new pontiff.
The Vatican spokesman, the Rev. Federico Lombardi, said the pope's pledge was in keeping with this effort to "explain how he intends to live this unprecedented situation of an emeritus pope."
"He has no intention of interfering in the position or the decisions or the activity of his successor," Lombardi said. "But as every member of the church, he says fully that he recognizes the authority of the supreme pastor of the church who will be elected to succeed him."
The issue of papal obedience is important for Benedict. In his last legal document, he made new provisions for cardinals to make a formal, public pledge of obedience to the new pope at his installation Mass, in addition to the private one they traditionally make inside the Sistine Chapel immediately after he is elected.
Benedict's resignation will be a moment of quiet theater.
At 8 p.m. sharp, the Swiss Guards standing at attention at Castel Gandolfo will go into the palazzo and shut the doors behind them and go off duty, their service protecting the head of the Catholic Church over — for now.
Lombardi said the guards would change into civilian clothes and return to the Vatican barracks Thursday night. They will continue to guard the entrances of Vatican City and the pope's palace, "even if he's not there," said Cpl. Urs Breitenmoser, a Swiss Guard spokesman.
And on Monday, the cardinals are expected to begin meeting to set the date for the conclave.
Benedict's decision has been met for the most part with praise and understanding. Cardinals, Vatican officials and ordinary Catholics have rallied around him in acknowledgment of his frail state and the church's need for a strong leader.
But Sydney Cardinal George Pell has caused a stir by openly saying the resignation has been "slightly destabilizing" for the church.
In an interview with Australian Broadcasting Corp., Pell noted that Benedict himself had acknowledged the shift in tradition; Benedict said Wednesday that he appreciated his decision was not only serious but "a novelty" for the church.
Pell also said the church was in sore need of a strong manager — comments echoed by several cardinals who have noted the 30-year reign of two popes who paid scant attention to the internal governance of the church.
The Vatican tried to downplay Pell's comments, saying it wouldn't respond to individual cardinals and urging the media not to take advantage of churchmen who, it said, aren't necessarily media savvy.
Winfield reported from Vatican City.
Follow Nicole Winfield at www.twitter.com/nwinfield
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