History is driven by what?

One of my favorite college advisers was a professor of English who also taught folklore. Years after I was out of college, I drove from my town to his and had lunch with him. A couple of things have stuck with me from that lunch, most notably his contention that, historically speaking, what actually happens doesn't matter nearly so much (in general) as what people think happened, and how they react. I thought it was just the folklorist in him talking. In other words, I didn't buy it, and wanted to dismiss it. But afterwards I kept my eyes open, and my mind, too, and I finally had to agree he has a point. Some day when I have more time, maybe I'll expand on that, but for now, why don't you chew on what George Wiegel said about what drives history?