Thanks to a mixed heritage, the catholic Christian tradition has always been pluriform in its notions of authority. During the Western Schism of 1378-1418, conflict between two types of theoretically interlocked authority, papalist and conciliarist, reached a fever pitch. The battle between these views consumed the fifteenth century and provided substantial ecclesiological preparation for the Protestant reformation in the sixteenth. Throughout the reformation and into the seventeenth century Protestants repeatedly invoked moderate conciliarist principles against the papacy's absolute monarchy. Standing on catholic conciliarism, the reformers worked for lawful, biblical reform of the Church. The Modern Protestant failure to soberly consider this essential backdrop leads us to distort the best parts of our own heritage, and to remain vulnerable to the half-truths of polemicized history on both sides of the Catholic-Protestant divide.