The theory does make some sense. We all try to do things that make us feel happy. We try to avoid things that make us uncomfortable or unhappy, unless by enduring those things we achieve something that ultimately makes us feel happy. Scott is basically saying that those kinds of reasons are why we do every single thing we do in life.
I don't know if he's right or not, and I'm not totally sure that Christianity actually fully explores the nooks and crannies of this kind of thought satisfactorily. But this morning something struck me. Does it really matter if free will "really" exists or not? It seems to us to exist, we act as though it exists, and so whether it is an illusion or not, we can at least consider it a useful concept and leave it at that. It's like... do we really "think" or do our brain cells just have chemical and electrical responses to stimuli? Well... does it matter? It SEEMS LIKE we're thinking. And it seems like we have free will, so for all intents and purposes, we do.