You know, it often does disturb me a little when I see evidence of how chemicals affect my mood in subtle ways. For instance, I notice myself getting more sarcastic and snippy to the people around me when my blood sugar is low (I'm a little hypoglycemic). I notice that I'm less able to control my frustration at little things in similar cases.
At those points I do sometimes wonder how much of the brain process is deterministically chemical, and how much can be "controlled" by "me," the personality that seems to be thinking my thoughts. The thing is, if I'm aware of how my lack of blood sugar affects me, I can clamp down, refocus, and avoid saying things that I'll regret. As I've lived with this for a few years, that gets a little easier.
So I guess what I'm saying is that I'm aware of the issues of chemical control of mood and thought, but there always is the illusion of "me" that can push through those factors and focus on what "I" need to be doing. I'm trying to figure out what sort of evidence would be necessary to break that illusion in a really disturbing, "stop me from functioning in a normal way" kind of way. I'm not sure what it would be, exactly. I'll have to pick up Scott's book when it comes out to find out!