Thanks for the clarification. ;)

Medieval authors have a tendency to assert or assume things like dog-headed people living in Eastern Europe or hot springs getting their heat from the fires of purgatory. No modern scholar would stipulate either of those as true in the Middle Ages, so I guess there's a sense in which you could call that "fact-checking."

But what goes on in medieval scholarship is not really "fact-checking" in the sense of modern journalism. Medieval sources don't typically lend themselves to kind of "facts" that we read on Wikipedia.

For example, Bernard of Clairvaux never wrote a letter saying, "Dear Abbot Peter, we're stealing a bunch of your monks and potential monks and cordoning them off in Citeaux, where we'll split western monasticism forever and get a lot of land and money from the aristocrats who prefer our austere lifestyle to your wasteful singing."

Instead, we have a collection of documents called charters, scattered among the different "Cistercian" monasteries in France and the Low Countries. These transfer tracts of land from nobles to the communities of nuns and monks. Other records demonstrate the increased productivity of these lands under Cistercian ownership, suggesting that either these monks or people they hired had lives of more strenuous labor than their Benedictine counterparts.

This example illustrates two of the main principles that medievalists can use when understanding what sources tell us about the Middle Ages. First, we can contextualize one source by using others. One charter in this case tells us about one transfer of land. One hundred charters with similar language tell us this is a standard practice. They don't just "confirm" or "fact-check" each other. They add up to a story.

Second, this case demonstrates that sources don't "tell" straightforwardly; scholars must interpret them. By studying ALL the charters from medieval Europe, not just this narrow sample, scholars learn the tropes and lingo of charters--learn what the language means. If you followed the recent case where Naomi Wolf utterly misinterpreted 19th century English court records, that's a great example. 19th century scholars know to interpret "Death recorded" as someone not being executed.

And that's just a case of direct language. We also learn how to tell what kinds of things the sources say about the past. For example, Mechthild of Magdeburg describes a divine vision of hell, of herself touring hell--think one of the inspirations for Dante's Inferno half a century later.

It's not that important to historians whether Jesus "really" took Mechthild on a tour of hell. If we want to understand medieval religion, it's important that we know (a) that Mechthild believed she went on this tour (b) that the people who read the book she wrote it in, accepted her account as valid (c) other accounts of voyages through hell written earlier are similar, showing that she was aware of some of them and that they influenced her own ideas of what 'hell' should look like; and so forth.

Learned how to read and interpret sources critically has been a long process that is definitely ongoing--and will continue to develop, as scholars read different sets of sources together, find new sources, and ask different questions that help us realize other things that the sources can tell us.

It's not "fact-checking" in the journalistic sense, but more like understanding.

Do you mean, did the authors in the Middle Ages fact-check what they were writing? Or are you asking, do modern scholars verify what they read in medieval books?