Pope Benedict XVI waves in St. Peter's Square in the Vatican in December 2012. Benedict, 85, announced on Monday, February 11, that he will resign at the end of February "because of advanced age." The last pope to resign was Gregory XII in 1415.
Joseph Ratzinger, who became the 265th pope in 2005, poses for a photo while a German air force assistant in 1943.
Cardinal Joseph Ratzinger, right, poses for a picture in Vatican City in June 1977 with fellow cardinals, from left, Cardinal Gappi, Cardinal Tomazek, Cardinal Gantin and Cardinal Benelli. Ratzinger was named cardinal-priest of Santa Maria Consolatrice al Tiburtino by Pope Paul VI in June 1977.
Ratzinger, who was serving as cardinal-priest of Santa Maria Consolatrice al Tiburtino, visits Madrid in 1989.
Ratzinger fills in for Pope John Paul II during the Easter Vigil service in Saint Peter's Basilica in March 2005.
Newly elected as pope, Benedict XVI gestures to the crowd in St. Peter's Square in Vatican City on April 19, 2005.
Benedict meets Prince Albert II of Monaco at the pope's private library in Vatican City in December 2005.
Benedict kisses the altar before addressing the crowds at Jasna Gora Monastery in Czestochowa, Poland, in May 2006.
Benedict waves from under an umbrella as he arrives to lead his weekly general audience in Saint Peter's Square at the Vatican in October 2007.
Benedict speaks at the United Nations General Assembly in New York in April 2008.
Benedict celebrates a Mass at the end of a synod of Catholic bishops in October 2008 at St. Peter's Basilica at the Vatican.
Benedict attends a screening of a movie about his predecessor, Pope John Paul II, on October 16, 2008, in Vatican City during celebrations of the 30th anniversary of John Paul's election as pontiff.
Benedict kneels as he prays in front of Pope John XXIII's tomb in St. Peter's Basilica at the Vatican on October 28, 2008, to commemorate the 50th anniversary of John's election to the papacy.
Benedict talks with bishops in Saint Peter's Square at the Vatican after his weekly general address in November 2009.
Benedict blesses pilgrims as he arrives in St. Peter's Square in his popemobile in March 2010 to meet with young people from Rome and the Lazio region in preparation for World Youth Day.
The pope salutes from his popemobile in St. Peter's Square in March 2010.
Benedict prepares to celebrate Mass at San Giovanni della Croce parish in Rome in March 2010.
Benedict prays on Good Friday in April 2010 at the Roman Colosseum.
Benedict celebrates an open-air Mass in the Terreiro do Paco in Lisbon, Portugal, in May 2010.
Benedict prepares to celebrate a Mass for 70,000 people in September 2011 in Berlin.
Benedict waves to the crowd gathered at the Colosseum in Rome during the Way of the Cross procession on Good Friday in April 2012.
A gust of wind blows Benedict's collar into his face in September 2012 during his weekly address in Saint Peter's Square.
Benedict speaks with Nikolaus Schneider, praeses of the Evangelical Church in the Rhineland, before a Mass at the Augustinian monastery in Erfurt, Germany, in September 2011.
Benedict waves to pilgrims as he arrives at St. Peter's Square for his weekly address in October 2012.
Benedict looks at a chess game with Ivory Coast President Alassane Ouattara during a private audience in November 2012 at the Vatican.
Benedict arrives to lead the Vesper prayer with members of Rome's universities in December 2012 at St. Peter's Basilica.
Benedict clicks on a tablet to send his first tweet from his account @pontifex at the Vatican in December 2012.
Benedict celebrates Mass during a visit to San Patrizio al Colle Prenestino parish on the outskirts of Rome in December 2012.
Benedict blesses members of the ecumenical Christian community of Taize, a group based in Taize, France, in St. Peter's Square in December 2012.
Benedict, accompanied by Grand Master Matthew Festing of the Sovereign Military Order of Malta, right, shakes hands with a woman after the Mass in St. Peter's Basilica to mark the 900th anniversary of the Order of the Knights of Malta on February 9, 2013, at the Vatican.
Pope Benedict XVI
Pope Benedict XVI
Pope Benedict XVI
Pope Benedict XVI
Pope Benedict XVI
Pope Benedict XVI
Pope Benedict XVI
Pope Benedict XVI
Pope Benedict XVI
Pope Benedict XVI
Pope Benedict XVI
Pope Benedict XVI
Pope Benedict XVI
Pope Benedict XVI
Pope Benedict XVI
Pope Benedict XVI
Pope Benedict XVI
Pope Benedict XVI
Pope Benedict XVI
Pope Benedict XVI
Pope Benedict XVI
Pope Benedict XVI
Pope Benedict XVI
Pope Benedict XVI
Pope Benedict XVI
Pope Benedict XVI
Pope Benedict XVI
Pope Benedict XVI
Pope Benedict XVI
Pope Benedict XVI
STORY HIGHLIGHTS
- Kevin Clarke: Pope Benedict XVI's decision to resign caught papal watchers off-guard
- Clarke: But canon law allows papal resignation; it's tradition that popes reign till death
- Benedict said a pope is obligated to resign if he can't handle duties
- Clarke: Whoever is chosen will deal with huge challenges facing Catholic Church
Editor's note: Kevin Clarke is the associate editor of America magazine, a national weekly published by the American Jesuits that reports on issues surrounding Catholicism, including news, book reviews, the arts and opinion.
(CNN) -- Pope Benedict XVI's decision to resign caught a lot of Vatican watchers, apparently even some in his inner circle, off-guard. They should not have been so surprised.
Canon law includes a provision for a papal resignation. But traditionally, popes continue their reigns until their natural deaths, much as a father can never "resign" from his place in a family.
Before he was pope, as Cardinal Joseph Ratzinger, Benedict watched an increasingly frail Pope John Paul II struggle to shoulder his many responsibilities and respond, in his final years, to the scandal of the clerical sexual abuse crisis in the United States and Europe.
Kevin Clarke
Another reason it is not a shock: In Peter Seewald's "Light of the World," a book-length interview with Benedict, the pope was unambiguous about his openness to the idea of papal resignation.
Too tired to go on, Pope Benedict resigns
Yes, a pope could resign, Benedict said. "If a pope clearly realizes that he is no longer physically, psychologically and spiritually capable of handling the duties of his office, then he has a right and, under some circumstances, also an obligation to resign."
And by some accounts, Benedict made three pilgrimages to the tomb of Pope Celestine V, who resigned from the papacy in 1294.
So what comes next? Presuming that this pope's resignation follows the same protocol as the death of a pope, all major decisions and pronouncements will be on hold after Benedict's reign ends February 28. The See of Peter will be vacant -- officially "Sede Vacante."
Watch Pope Benedict XVI resign
Abuse by priests mars pope's legacy
Pope Benedict's influence will linger
Who will be selected as the next pope?
During the vacancy, Cardinal Tarcisio Bertone, the Holy See's camerlengo, Italian for chamberlain, takes charge with the help of three cardinal assistants.
To prevent forgery, Bertone will break the pope's fisherman's ring by hitting it with a small hammer, a tradition that was started when the ring was used to seal documents. Benedict's apartment will be sealed to prevent any hijinks with official documents.
Opinion: Why pope will be remembered for generations
Bertone will organize a conclave of 118 cardinals, who must meet in Rome within 20 days of the end of Benedict's reign to deliberate on a successor. White smoke rising from the Sistine Chapel's chimney will indicate a selection.
Guessing who that selection might be, one of the church's favorite spectator sports, has already begun among papal watchers worldwide.
Among the "papabile," or possible contenders, are Cardinal Angelo Scola, archbishop of Milan, which would return the job to an Italian; Cardinal Marc Ouellet, former archbishop of Quebec; Cardinal Peter Turkson of Ghana, president of the Pontifical Council for Justice and Peace, which would be a nod to the African church's growing numbers and influence; and Joao Braz de Aviz of Brazil, indicating a liberating take on the church in the future.
The Pope's resignation, explained
How about Cardinals Donald Wuerl or Timothy Dolan from the United States? They are outside contenders. The rest of the world thinks Americans are super-powered enough already.
Whoever is chosen will face the many challenges that Pope Benedict has no doubt wisely decided he no longer has the stamina to address, including:
• The growing secularization and antipathy of the West.
• Violence and intolerance visited on Christians in Islamic nations like Pakistan, Egypt and Syria.
• The evaporating Christian presence in the Holy Land, Iraq and elsewhere in the Middle East.
• More brutal revelations of clerical sexual abuse in Africa and Latin America, which have yet to adequately confront the problem.
• The ongoing priest shortage.
• Plummeting church attendance.
• Growing calls for optional celibacy.
• Persisting demands for women's ordination and more.
Is there somebody out there who really wants this job?
Surprising standards for next Catholic leader
Perhaps now, with confidence that a new precedent has been set and an actual well-deserved retirement would not be completely out of the question, someone will be courageous or foolhardy enough to step forward. And in an oddity of church tradition, that person need not be a cleric, only a baptized male. So if you are, feel free to submit your application to the College of Cardinals.
Meanwhile, let us pray whoever is the next pope is also equipped with compassion, mercy and vision.
Follow us on Twitter @CNNOpinion.
Join us on Facebook/CNNOpinion.
The opinions expressed in this commentary are solely those of Kevin Clarke.