Yes. But it remains a part of me. Which was the point in question.
It isn't, though. It absolutely requires inputs from beyond your body in order to function at all. A brain without external stimuli and nutrients is just a lump of carbon slowly decaying into the soil, not even salvageable let alone functional.
We look back on our day and think "I was mad at Steve because he was an asshole", not "I was mad at Steve because there was an unpleasant odor in the workroom and it set off my insular function, which then tripped my amygdala, which set off damn near my entire network towards looking for potential threats, which it found in Steve's facial expression precisely because by that point my brain was searching for any explanation as to why it was freaking out, but I'd already habituated myself to the smell roughly three seconds before and no longer perceived at all, so Steve's smirking-ass face presented itself as the most likely source of my feeling of unease, and because I'm a primate with a typically overactive temporal parietal junction, I assumed agency and intention on his part rather than pondering how my own perception might have been the true source that sense of agency of intention".
But any neuroscientist knows which of those scenarios is far, far more plausible. Common sense is a comforting concept, but an inaccurate methodology.
Sure. We don't disagree at all on any of this
Including the fact that in both scenarios it is
I who is mad at
Steve.
Nobody is so much as hinting that there is uncertainty about which bits of the universe are Steve, which are me, and which are neither of us.
So all of this is irrelevant to the question of whether I (or Steve, or anybody else) makes choices.
I choose things. If nobody forces my hand, I do so freely. I am responsible for my choices and their consequences.
Not the Big Bang; Not the laws of physics; Not the gods or the fates; Me.
Except that the person who used too much Glen-20 when cleaning the room that morning had a
lot more to do with it than Steve did, or even you did. If they didn't overdo it with the damn disinfectant, none of it would have happened. You didn't "choose" to be irrationally angry at Steve, and Steve certainly didn't have anything to do with it. You were never even consciously aware of the real source of your ill emotions, it never rose to your conscious awareness at all. You don't remember choosing to be mad at Steve. You perceive the entire situation as being the result of the choices that
Steve made. But it's quite likely Steve didn't even know about the situation until you dropped a hammer on his hand for reasons even you didn't remember anymore and he never understood at all. Your accounts of the argument and whose "choices" led to it will never be reconcilable, and are likely impossible to investigate by the time the most critical incident occurs. The workroom doesn't smell gross anymore, and it wouldn't occur to either you or Steve to look back far enough in time to remember the odor at all, let alone attribute the argument to it, nor would your boss believe for a second a bullshit answer like "the Glen-20 made me do it". Understandably. I wouldn't either. We are captives to our senses. But the answer that involves the insula/amygdala interaction has the important advantages of both lying much closer to the observeable world rather than the world of emotional perception, and also of explaining why both you and Steve feel strongly but inaccurately that the inexplicable "choices" of the other party - the unknown, threatening circumstances of why "Bilby just lost it all the sudden, for no reason" or "Steve's been hounding me for weeks, for no reason" - yet neither of you can present a speck of evidence for your passionate views on the matter. Of course, you will eventually bear the penalty for the incident. But not because Steve's perception is more accurate. Only because at the end of this whole complex neurochemical process beginning in one person's mind (the janitor) and ending in three others (you, Steve, and your boss) the only one left holding a hammer was you.
Well, until you dropped it on Steve's hand of course.