Theologians agree that there have been only two papal statements that fall into the infallible category – the Immaculate Conception in the Nineteenth Century and the Assumption in the Twentieth. In both case the popes claimed to be giving expression to the faith of the Church as it could be traced back to apostolic times. In neither case did they give a philosophical or theological explanation of how these dogmas should be interpreted. They simply gave voice to the faith and practice of believers. What was being said about Mary expressed the ideals for which the Christian community was striving. Believers were not asking whether Marian doctrine was to be interpreted in a particular biological sense; they knew it had nothing to do with the purpose for which the teachings were being proposed. Neither did the papal definitions answer those questions, but simply encouraged devotion through which believers expressed their desire to live the Gospel.
Because most Catholics had assumed a static and unified Church organisation, it was easy to assume that this pattern was more or less set by Christ and should never be changed. The study of history shows that it was all changing all the time, and that it looked very different at some times, so much so that we have to ask what is of the divine and necessary plan and what is simply a human attempt to organise life in community as best serves its purpose. Whatever belongs to this category can obviously be changed again when the times call for it.
There is ongoing research into collegiality and the relation between pope and bishops. When Vatican I passed the Constitution Pater Aeternus there were two issues at stake concerning the pope. His power to command and rule in dioceses other than his own, and the question of infallibility. It is not possible to assume that the pope cannot make mistakes, or even fall into heresy. Classic Canon Law says: if the pope falls into heresy he must be deposed. The law considers it most unlikely, but provision must be made for the possibility. If they had held the hot line theory they would never have considered even the possibility of this happening.
Infallibility is severely restricted; an interesting point, because some believed – including some bishops – that the Pope was always infallible and could never make a mistake in teaching Christian doctrine. The Council clearly disagreed, attributing absolute authority only to God. It declared that the Pope possesses only that infallibility which God willed to give to the Church, whenever he solemnly and officially defines a doctrine to be held by the whole Church concerning faith or morals.