Christopher Tyerman's body of work on the Crusades is really interesting in this regard. One of the key points he keeps pressing home, is that though we think of Medieval people as ignorant and superstitious, they were in fact highly rational. And they were as a culture committed to rational investigation of the world.

But they had axiomatic beliefs that they were building upon. Which meant they were also committed to a rational investigation of the supernatural world. Which we generally view as non-rational.

I'm very much paraphrasing and he would not express it so crudely.