Christianity

The priest who spent decades pleading against enslaving Native Americans initially told Spain to import Africans instead, then wrote in his own history that he had come to see that stance as equally unjust, a reversal historians rarely put beside his more famous advocacy.

The two earliest accounts of the vision that supposedly turned Constantine to Christianity do not even agree on whether he was asleep or awake when he saw it.

Only one ancient writer ever names Cyril of Alexandria as responsible for Hypatia's murder, and that writer also demeaned her intellect elsewhere in the same text, a contradiction later admirers of Hypatia rarely mention.

Joan of Arc's own words survive in unusual detail because two hostile courts, one convicting her and one clearing her decades later, both wrote everything down.

Every detailed account of Nero was written decades after his death by a senatorial class his reign had offended, and the three main sources cannot even agree with each other on what happened.

England's most celebrated medieval king spent perhaps six months of a ten-year reign actually in England, a fact twentieth-century historians turned into a damning verdict before more recent scholars pointed out he had an entire continental duchy to defend as well.

Four states built by a permanent minority of settlers, which lasted nearly two centuries only because their Muslim neighbours were often more interested in fighting each other.

Medieval chroniclers could not even agree on what Pope Urban II promised the men who signed up for the First Crusade, and historians still argue how much religion had to do with any of it.