Later histories placed the reign of Pope Joan between the reigns of Leo IV and Benedict III. Leo died and Benedict was elevated in 855. But could a female pope have ruled then?
Among the commonfolk, the date, six centuries prior, must have seemed plausible... unless one knew what was going on just after 855: The Photios controversy.
The emperor of Constantinople had deposed the Patriarch of Constantinople. All the priests of Constantinople were loyal to him, however, so no successor could be chosen among them. Therefore, the emperor elevated a layman to become bishop. The bishop of Rome, the pope, siding with the deposed patriarch, objected that such an elevation was improper. The emperor insisted the Roman patriarch had no such authority to object. Thus began the controversies which would result in the Great Schism between Orthodox and Catholic churches.
So, according to the Pope Joan legend, this all unfolded immediately following Pope Joan. How could extensive debates which followed never make any reference to the supposed fact that the See of Rome had just been occupied by someone canonically unfit to be a bishop? To the fifteenth-century scalliwag, A.D. 855 seemed like a remote and unknowable date. But to a historian, it was a particularly well-documented and well-detailed era of Catholic history.
So why create such a scurrilous tale if it were truly fictitious?
The legend probably comes from Pope John XI, not, as the story would have it Pope John VIII. John XI was from Italy, not England. John’s mother was ruler of Rome. He was a weak, ineffectual ruler, dominated by her, until she was overthrown. Then, he was afforded virtually no temporal (”secular”) power. His reign was considered by many to be the deepest humiliation of the papacy. Pope Joan may be a conflation of John XI and his mother, whom critics may well have scoffed was a “de facto pope.”
As early as the 15th century, when the first stirrings of what might be called a more disciplined approach to history had begun, the story of Joan was being called into question. When the fable was used as anti-Catholic fodder during the Reformation, Catholic historians began to question its historicity. And soon, oddly enough, their perspective was confirmed by a French Calvinist historian.David Blondel (1590-1655) was a Protestant living in the Netherlands who effectively used the early tools of historical study to dismantle the myth of Pope Joan. Tracking the history of the popes during that period and the lack of any contemporary mention of Joan in what would have been, if true, an astounding event to be exploited by papal enemies, he dismissed the legend. His fellow Protestants of the era dismissed Blondel because, as Pierre Bayle said, "the Protestant interest requires the story of Joan to be true."
But the story is protean, so it persists. These days, it serves the secular agenda as an example of the supposedly "hypocritical" origins of priestly celibacy and the all-male clergy in the Catholic Church. The presumption is that such propaganda will cause the Church to change her practice in these areas. That's not going to happen, of course, but it will be an effective polemic in certain circles against the Church's moral teaching.
Eventually, the story will probably serve as the first combination foot ointment and salad dressing.