VATICAN CITY (AP) -- He slipped it in at the end of his speech, and said it so quickly and softly it almost sounded like an afterthought.
But in pledging his "unconditional reverence and obedience" to the next pope, Benedict XVI took a critical step toward ensuring that his decision to break with 600 years of tradition and retire as pope doesn't create a schism within the church.
It was also a very personal expression of one of the tenets of Christian tradition that dates back to Jesus' crucifixion: obedience to a higher authority.
In the two weeks since Benedict announced he would resign, questions have mounted about how much influence he would still wield and exert over the new pope.
Benedict will continue to live inside the Vatican, wear the white cassock of the papacy, call himself "emeritus pope" and "Your Holiness" and even have his trusted aide continue living with him while keeping his day job as head of the new pope's household.
The Vatican has insisted there should be no problem with a reigning and a retired pope living side-by-side, that Benedict has no plans to interfere and that as of 8 p.m. Thursday, Benedict was no longer pope.
But the real concern isn't so much about Benedict's intentions as it is about how others might use him to undermine the new pope's agenda or authority.
"There is the risk that Benedict is aware of that some people could claim in the future that they want allegiance to Benedict and not the next pope," said the Rev. Robert Gahl, a moral theologian at Rome's Pontifical Holy Cross University. "He wants to preclude any division in the church."
One needs only to look at the last time a pope abdicated to understand how real that risk was, at least in history: Pope Gregory XII stepped down in 1415 as part of a deal to end the Great Western Schism, when dueling papal claimants split the church.
Gregory and all the cardinals who elected him pope in 1406 had pledged to abdicate if the rival Pope Benedict XIII in Avignon, France, did the same. While the endgame didn't work out exactly as planned, Gregory did step down and the split was eventually healed.
The "shock" of that schism "certainly influenced the collective mentality of the church of Rome" and contributed to the tradition of popes reigning until death, church historian Giovanni Maria Vian, editor of the Vatican newspaper L'Osservatore Romano, said.
Today, the Catholic Church already has fringe groups not in full communion with Rome, such as the ultra-traditionalist Society of St. Pius X, with whom Benedict took extraordinary measures to reconcile during his eight years as pope.
If the next pope were to roll back some of Benedict's overtures toward the group, which included allowing greater use of the pre-Vatican II Mass in Latin, some of its members could try to pressure the new pope by saying "'We want to be in full communion, but only if Benedict accepts us,'" noted Gahl.
By pledging his own obedience to the new pope, Benedict has undercut any such scenario.
Benedict also took measures to ensure that the election of his successor was free of any possible claims of illegitimacy, in another bid to thwart those who might still claim him as pope. He issued a final legal document giving the College of Cardinals the right to move up the start date of the conclave.
The cardinals could have interpreted the previous rules as giving them that right, but Benedict made it crystal clear to avoid any suggestion that the election itself wasn't valid.
In that same document, Benedict also moved to ensure that his successor is viewed as the only legitimate pope by requiring the cardinals who elected him to make a public pledge of obedience to him during one of his first Masses as pope. Under previous rules, the cardinals only make that pledge in the privacy of the Sistine Chapel immediately after the election.
"They represent the whole church, the universal church," Gahl said of the cardinals, adding that such a public show of deference to the new pope's authority was a powerful message to all believers.
But while his primary aim may have been to ensure a smooth transition to the next pope, Benedict was also voicing his own expression of submission to authority that that underlies Christian tradition dating from Jesus' act of obedience to God in dying on the cross.
Christians believe that Jesus died to save them from their sins.