Many years ago when my religious doubts were still in flux, I spent some time in Christian chat rooms and would often ask people why they believed whatever they believed, without being confrontational. It emerged that most people seemed not to know why they believed, or at least were unable to express it. They just believed -- probably because they'd been taught to believe as children, though that's not always the case. I did encounter a handful of people who were able to get into the "why" a bit...

But on the other hand, a Christian friend of mine, who is a science educator and a very intelligent person, recently told me that he had spent a lot of time and effort studying to make sure that what he believed was true. And he had concluded that it is in fact true. I didn't know where to go with that, without risking the loss of a friend, so I let it be. But privately I was baffled.