Joseph Lortz was a German Roman Catholic theologian. He's best known for his work on Martin Luther and the Reformation. In his book The Reformation: A Problem for Today (Maryland: The Newman Press, 1964), he has a chapter entitled "The Causes of the Reformation." One particular "cause" caught my attention. He states,
"When Luther asserted that the pope in Rome was not the true successor of Saint Peter and that the Church could do without the Papacy, in his mind and in essence these were new doctrines, but the distinctive element in them was not new and thus they struck a sympathetic resonance in the minds of many. Long before the Reformation itself, the unity of the Christian Church in the West had been severely undermined" (p. 37).
This type of sentiment is far different than that usually expressed by Roman Catholics. Typically, Luther is the grand innovator that tore the church asunder. Lortz though does something many don't bother to do- he sees a flow to history. In his chapter preceding this statement, he lists a number of ways in which the West was more than ready to grant that the pope in Rome was not the true successor of Saint Peter and that the Church could do without the Papacy. Here's how Lortz explains this comment:
The significance of the break-up of medieval unity in the thirteenth century, but even more during the Avignon period, is evident in the most distinctive historical consequence of the Avignon Papacy: the Great Western Schism. The real meaning of this event may not be immediately apparent. It can be somewhat superficially described as a period when there were two popes, each with his own Curia, one residing in Rome, the other in Avignon. This situation in which both contenders claimed to be pope (at one time the number increased so that many spoke of the "cursed trinity") was in the main corrected by the efforts of the German Emperor Sigismund at the Council of Constance in 1414. These statements are true, but the account they give is sketchy and superficial; they tell us nothing of the real significance of the Schism.
The real significance of the Western Schism rests in the fact that for decades there was an almost universal uncertainty about where the true pope and the true Church were to be found. For several decades, both popes had excommunicated each other and his followers; thus all Christendom found itself under sentence of excommunication by at least one of the contenders. Both popes referred to their rival claimant as the Antichrist, and to the Masses celebrated by them as idolatry. It seemed impossible to do anything about this scandalous situation, despite sharp protests from all sides, and despite the radical impossibility of having two valid popes at the same time. Time and time again, the petty selfishness of the contenders blocked any solution.
The split caused by the Western Schism was far from being merely the concern of theologians; no area of public or private life remained untouched; even the economic sphere was affected, mainly because of disputes in regard to the possession of benefices. Provinces of the Church, religious orders, universities, even individual monasteries and parish houses were divided. For decades, all experienced this profound division in all sectors of daily life. Good people on both sides, even saints, were not only unable to bring about unity, but in their allegiance to one or the other of the contenders they themselves were in sharp opposition. We find, for example, St. Catherine of Siena on the Roman side and St. Vincent Ferrer on that of Avignon. Furthermore, the settlement of the Schism at the Council of Constance did not really solve the problem. The triumph of the Conciliar Theory at Constance, and even more at Basel, extended the life span of the Schism from 1378 to 1448, when it finally came to an end in the person of the Antipope Felix V. The confusion and uncertainty about the valid pope and the true Church is manifest in the amazing twists in the allegiance of Nicolaus of Cusa and Aeneas Silvio dei Piccolomini, later to become Pius II, both of whom had begun by defending the Conciliar Theory in its most radical form.
This was an experience shared by the entire West — one which would leave its imprint in Western consciousness for a long time to come. The memory of this experience was still fresh a century later. It is not too difficult to see the effects of the Western Schism in preparing the way for the doctrines of the Reformation. When Luther asserted that the pope of Rome was not the true successor of Saint Peter and that the Church could do without the Papacy, in his mind and in their essence these were new doctrines, but the distinctive element in them was not new and thus they struck a sympathetic resonance in the minds of many. Long before the Reformation itself, the unity of the Christian Church in the West had been severely undermined (pp. 35-37).