Oh, they may have heard, for instance, about anti-Judaism in Christian history (for my essay on the subject, look under the "Check this out" headline on the right side of this page), but mostly they cannot cite chapter and verse.
And though they are vaguely aware of something called "The Crusades," the details pretty much escape them.
Today is a good day to begin to rectify some of the ignorance about the Crusades, for it was on this date in 1095 that Pope Urban II, speaking at the Council of Claremont in France, declared the necessity of the First Crusade, meant to make the way safe for pilgrims between Europe and the Holy Land and, if possible, to wrest control of Jerusalem and the surrounding area from the Muslims.
As historian Steven Runciman reports in volume one of his three-volume A History of the Crusades, four contemporary chroniclers reported the pope's words, but they are a bit contradictory and it's unclear whether any of the four was really present.
Nonetheless, he urged Europeans, as Runciman says, "to march to the rescue of the East." And as he spoke, cries of "Deus le volt!" ("God wills it!") rose from the crowd.
Although Christians did manage, temporarily, to capture Jerusalem, the result of more than half a dozen crusades (it depends on how you count them) over a couple of hundred years was disaster. Christianity's relations with both Muslims and Jews were made many times worse, and it can be argued that there's not been a full recovery even today.
The Crusades, though quite understandable in the context of their medieval time, wound up as one more major piece of evidence in the case against religious zealotry and false certitude. That humanity has not either learned or retained that lesson is obvious today in many parts of the world, and it's one reason faith itself has so many serious detractors.
(By the way, the map here today came from http://www.islamproject.org/education/The_Crusades.html.)
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What in the world is a "faitheist"? The assistant humanist chaplain (you read that right) at Harvard University explains in this interview. I suppose this makes fans for the Missouri Tigers' men's basketball coach Haitheists.