Last Sunday, New York's Cardinal John O'Connor celebrated his last Mass as leader of 2.4 million Catholics. The cardinal had just turned 80, which meant he was no longer eligible to vote for new popes and must be replaced. "Does anybody have a job for me?" he jokingly asked the crowd. While it's policy for aged cardinals to retire, suggesting the same of a pope can cause a real stir. A German bishop accidentally made headlines just a few weeks ago for reportedly calling on the elderly Pope John Paul II to step down. The bishop moved swiftly to smooth things over. After all, the last time a pope resigned was 1294, and the issue then was much more complicated (and dubious) than old age.

In the thirteenth century, the church and the papacy tended toward wealth, worldliness, and political power. A reforming faction, which included many monks and hermits, longed for a leader who would purify the church and thus, they believed, hasten the return of Christ. The division between the two camps was so deep that, when Pope Nicholas IV died in 1292, church officials took 27 months to select a replacement. They finally elected Peter of Marone, founder of the Hermits of St. Damian, hoping he would be a "Papa Angelicus"—an unworldly saint with power to transform the church.

Unfortunately, Peter (as Celestine V) was spectacularly ill-suited to be pope. Already 85 at his election, he had spent much of his life as a recluse in a mountain cave. When bishops fetched him for his new office, they discovered a pale, unkempt, unhealthy man who could barely understand what they wanted. Nonetheless, they brought him back to Aquila, Italy, where he was crowned before 2,000 people. He moved to a palace in Naples, but his ascetic habits remained: he build ...