The Schism in the Church was first and foremost a schism in the College of Cardinals, a schism that lined up generally with the sides of the contemporary Hundred Years War between England and France. Once there were two lines of popes established, however, it became very difficult to conceive of a solution. One theory that was advanced was that a council—dominated of course by the cardinals—was in fact the highest authority in the Church. What this meant was that a council could depose both popes and elect a new one. In 1409, during a period of peace in the Hundred Years War, when the belligerent countries had less interest in “winning” the schism, cardinals from both popes defected and met in council in Pisa. They deposed the rival popes and elected a third. Of course, neither the Roman nor the Avignon pope recognized the depositions as valid, and so the Church was left with three popes. This situation was totally unacceptable and whatever support the rival popes could maintain began to erode in favor of the conciliar solution. Gregory XII, the legitimate pope of the Roman line, was not willing to allow the power of the papacy to be completely gutted by a council, and so he agreed that if a council deposed the two anti-popes, he would approve its acts and then resign himself, leaving the council to elect a new pope for the whole Church. This is exactly what happened at the Council of Constance in 1415. Gregory XII resigned and became the Dean of the newly re-united College of Cardinals. The council, however, did not proceed to the election of the next pope, Martin V, until 1417, after Gregory had died. So, the potentially problematic situation of having two popes alive at the same time was avoided.
With the election of Martin V, the papacy entered a new phase in its history. The strength of the Church as an institution had been severely weakened by the schism. Not only had the papacy’s prestige been hurt immensely, but over the course of the conflict, both papal lines had traded away a great deal of their governmental powers to the various princes of Europe. By the time the schism ended, the papacy had a fraction of the institutional power in the Church that it had in the mid-14th century. In fact, it is not too much of a conceptual stretch to start seeing Europe as a collection of national churches, led by their monarchs, yet united in doctrine. The constellation of circumstances that had led to the immense power of the cardinals and to the problems of papal vacancies and ultimately schism had largely faded away, and the papacy began facing a new problem, that of how to retain its independence from powerful monarchs who had near absolute control over the churches in their kingdoms. The solution was for the popes to construct their own church/kingdom in central Italy, which became the major project of the Renaissance papacy.
As we have seen, there have been three periods in which papal resignations have occurred. In each one the resignations were an aspect of the Church’s attempts at dealing with some crisis. In the ancient period, the problem was that of persecution; in the eleventh century it was the problem of corruption and irregular elections; in the High and Late Middle Ages the problem had to do with the power of the cardinals and the interference of increasingly powerful kingdoms in the election of popes, leading to long papal vacancies. In each case, though, the resignations themselves were largely incidental to the solution to the problem at hand. What Benedict XVI is doing is, therefore, novel. Because the Holy Father seems to be suggesting papal resignation itself as the solution to the problem of aged pontiffs in the fast-paced modern world. Benedict is suggesting that the Church requires a pontiff of a certain vigor and that when he is no longer capable of performing at this level, it is appropriate for him to step down. If this is the case and if papal resignations become a viable, even a normal, way for pontificates to come to an end, it will be a development in the papal office of the same magnitude as the eleventh-century constitution of the cardinals as papal electors or the thirteenth-century establishment of the Conclave. For this reason, it is a mistake to view the primary historical interest of Benedict’s resignation to be simply that papal resignations are rare and haven’t happened in a long time. Rather, we are potentially witnessing major development in the papal office. As with so many things in the Catholic Church, only time will tell.