In an unexpected move, Pope Benedict XVI has tendered his letter of resignation from the Papacy. This is the only resignation in the modern era, and I believe only the second resignation from the Papacy in the history of the Roman Catholic Church. In his resignation letter Pope Benedict states:
"After having repeatedly examined my conscience before God, I have come to the certainty that my strengths, due to an advanced age, are no longer suited to an adequate exercise of the Petrine ministry.
"I am well aware that this ministry, due to its essential spiritual nature, must be carried out not only with words and deeds, but no less with prayer and suffering.
"However, in today’s world, subject to so many rapid changes and shaken by questions of deep relevance for the life of faith, in order to govern the bark of Saint Peter and proclaim the Gospel, both strength of mind and body are necessary, strength which in the last few months, has deteriorated in me to the extent that I have had to recognize my incapacity to adequately fulfill the ministry entrusted to me.
"For this reason, and well aware of the seriousness of this act, with full freedom I declare that I renounce the ministry of Bishop of Rome, Successor of Saint Peter, entrusted to me by the Cardinals on 19 April 2005, in such a way, that as from 28 February 2013, at 20:00 hours, the See of Rome, the See of Saint Peter, will be vacant and a Conclave to elect the new Supreme Pontiff will have to be convoked by those whose competence it is."
For the Roman Church, this will be a theologically interesting period. The only other pope to resign did so during a time of controversy in which many challenged whether he were the pope or not. This one is resigning “in good standing.” This means that previous to Pope Benedict, the assumption had grown that the pope does not merely hold the Petrine office, but is somehow, mystically, Peter. By his resignation, Pope Benedict is making the clear declaration that a pope holds an office, but does not, in himself, “become” Peter. That is, the office is not personalized, but is simply an office.
The Catholic Church, itself, has not had the experience of having a retired Pope around. They will have to decide how to address him, where to house him, what honors accrue to him, if any. Like having an ex-President in the USA, a person who has been President does not simply return to the life they had previously.
The East has had ex-Patriarchs, so we are more used to dealing with such matters. Even so, there is not much of that in the modern era. As I said, this will be an interesting theological period to come.