If you're treated a certain way you become a certain kind of person. If certain things are described to you as being real they're real for you whether they're real or not.
“What I like about the third movie is you get to see a side of Carlisle you haven't seen before. You actually get to see what his vampire capabilities are because there's some great battle sequences. It's my favorite book. Carlisle is holding on to that humanity. He doesn't want to be a vampire.”