Re “main cause” : I admit I didn’t have a particular precise idea of what I meant by this. I suppose I meant, some kind of combination of proximate cause and cause most useful to consider as “the cause”? So, not facts that are so complicated that people cannot comprehend them, and also things that are, in terms of causes people can understand, relatively direct ones? But yes, this is a rather imprecise idea, which could stand to be improved.

As for quantum mechanics and drawing boundaries between things, I do think quantum mechanics allows boundaries to be drawn. I don’t understand quantum field theory, and apparently the “Schrödinger picture” doesn’t (seem to?) exist for quantum field theory, which makes it hard for me to think about,
but for quantum mechanics, aiui, you can split up the Hilbert space into tensor products of Hilbert spaces for different parts of the system (e.g. “all the stuff going on in this region of space” vs “all the stuff going on in that other region of space” , or, “all the stuff with electrons” and “all the stuff with protons”, etc.)

And, while again, I don’t understand quantum field theory as well as I understand quantum mechanics (and, note: my understanding of that is also limited!), my impression is that the observables in quantum field theory, uh, when they are about causally separate regions of spacetime (meaning, neither can influence the other, though they may have common past influences and may both influence the same later thing), that the observables in question commute, and that this is how locality is implemented,

And so, this seems to fit reasonably well with the concept of there being “separate things”.

Then, (getting now into things I understand even less still, possibly even less than QFT), I think there is a quantum version of the idea of a Markov boundary, or Markov blanket, or something, such that the causal connections between two regions on opposite sides of this boundary, can be entirely accounted for by the connections between each of the two sides with the boundary.

So, I think this allows for like, drawing an envelope around an object and a given period of time (so, a cylinder-ish shape, where at the start and end of the time period there is a Cauchy surface covering all the object, and during the duration, the boundary of the region, overall making a kind of cylindrical 3D hyper surface?), and like, splitting up the world into the part inside and outside of this region, and talking about how two two sides evolve over time themselves, and then how the two parts interact?

So, all that to say, my impression is that it is possible within QM and QFT to define, like, objects. Not that there is a definition for “an object”, but that it should be possible to define particular objects.

> So how did the brain that sends the signals come into existence? Is the brain that sends the signals able to send the signals, because the body that supports it provides what it needs to operate?

I’m not really understanding your point here. The brain came into existence while the fetus/baby was in its mother’s womb. And without the support from the body (with nutrients and oxygen etc. being supplied to the brain through blood and such), the brain would fail to function/die, yes.

But I don’t see how this connects to the question of “does what we are (or, rather, what we are supposing that we are) ‘the’ cause of what it is that we do?”

I guess those questions are both about “why is the thing (or things) that we are supposing to be us (namely, the brain or brain+body or brain+body+papers etc.), the way that it is?”,
but, if “free will” is just “our actions are due to us” / “our actions are due to us being the way we are”, then I don’t think “why are we the way we are?” really poses an issue for that?

I suspect I have misunderstood your point and as such responded to something other than what you meant. If so, could you clarify / correct my misunderstanding?

That last bit I said of “if there are no people” was just addressing part of my earlier parenthetical where I gave “there are no people” as an alternative account of “what are people” under the assumption of physicalism. It was a minor (vacuous) point I was making for sake of completeness, and because I have a fondness for statements that are vacuously true.