Interesting stuff Stephen. I have to admit I never thought of free will in this way. That it can be as mechanistic as breathing or digesting and that “free” comes from the denial of those actions like you said in your “grabbing water” example. It actually reinforces my opinion on free will.
I always wondered how people with heavy addiction problems were able to get clean. For me that was evidence on the existence of free will. If the mind can control the addiction of a body conditioned in such heavy drugs then the only logical reason is that we indeed have free will. And then there are other examples of people who go against the biological imperative of survival and sacrifice themselves to save another. Campbell talked quite a bit about that I think.
We also need to take under consideration how much our conscious mind affects the unconscious. Jung said.
“Until you make the unconscious conscious, it will direct your life and you will call it fate.”
And then there is something else which might be a bit off topic, maybe relevant so just gonna say it.
You start your post by saying.
I concur with the idea of acting “as if” we have free will, but do we really? There is a case to be made that free will, in terms of conscious intention, is an illusion.
Maybe the illusion is the divisions we create. Maybe the illusion is our approach to time. My hypothesis is that we chose, despite how we divide it as a conscious/unconscious or as past/present antithesis. We chose to drink the water or not drink it and what does it matter if it happens in real time or 5 miliseconds later.
What matters is that we chose to perform or not perform that action. That is Proof. 🙂
Anyways.. I am not a scientist and not scientifically oriented so my answers tend to revolve on the philosophical and mythological realms.