Hence my question as to what you believe intervenes in these physical reactions to produce an outcome that is not determined by physics/chemistry/etc.
Nothing intervenes in it. I just don't think you can determine the single outcome that will happen in advance. The possible outcomes are still inherently limited by physics/chemistry/etc, and you can not get an outcome that falls outside of those limits.
Okay, good. So we have one point of agreement. But then....
I think that you can have multiple outcomes from the same starting parameters in a system that is sufficiently complex. What I'm not certain of is whether that complexity requires those quantum fluctuations or not.
Also agreed....to a point. RANDOM interventions will certainly cause multiple possible outcomes.
But here's the rub: since those random interventions are by nature random, they are clearly not a deliberate decision - not part of any "free will" process that involves considered and deliberate choice. So we can, effectively, exclude them.
So we have a scenario where the rules fo physics and chemistry apply, and where there is no random interventions. And THAT is the point at which you need to explain how identical situations, following identical physical rules, can come to different outcomes. Absolutely identical setups, remember - not just "pretty close", but identical all the way up and down.
By what process can different results be obtained? "Large systems" is not an answer, because every part of that system was set up the same, and every small process is governed by the same laws - so if every small reaction/part cannot change, nor then can the large outputs.
But remember - if the SGU, every element is reloaded exactly the same. So this neurone has this particular charge, that axon is in that particular state....if each one obeys the laws of physics and changes its state from moment to moment according to the (identical, remember) stimuli affecting it.....how do you end up with a different result?
I'm saying that all the jigsaw pieces are the same, and will - can - produce only one picture. You seem to be saying that - somehow - the same pieces can make 2 or more pictures. I'm just asking you how.
Imagine you made a save state of someone making a jigsaw puzzle. Let's say that the state was made before they'd decided on the picture to use for the puzzle. You're basically saying that, from the point at which things were saved, they'll always pick the same picture and cut the pieces the same way. I'm saying they might not. They might have two or three pictures which they like, and have to decide which one to use. So they might be more likely to pick one over the others, but it's not impossible that they'll choose one of the other two finalists instead.
But again....how? At the point the save was made, they had the same thoughts, preferences, experiences, loves, likes...and so on. But depite all those preferences, you are saying that the outcome can change, without being either stochastic or random.
I see a lot of "it can happen", but very little
why or
how it can happen.
I think that the processes that let us make decisions can interact in such a way that they will not automatically come up with the same decision, based on the same starting data.
I get that you do. But HOW?