Perhaps a bit of both really. He's become accustomed to people here having all sorts of magic. Plus he is a little on the stiff side. Obi-Wan does have a sense of humor but it's a dry and sarcastic sort.

"For as long as I can remember, yes. We call it the Force. It's an energy that is all around us and apart of us. Someone who is sensitive to it can manipulate it just as you did your shadows. So, yes, I think I understand."