A few things:
1. Mind-body Duality
Determinists must believe in Spinoza’s Monadology, which is the basis for Ontology (and Atomic Theory), because otherwise a Determinist would be forced into, as you say, “two types of cause” or “two types of sbustance/matter”. If there were “two types of causes” then it won’t make sense to say that “all things are caused” without knowing exactly which set or standard of ‘Causes’ there are. As an analogy, it would be equivalent to stating that there are “Two Laws” which govern the universe, one applied to this (not-Humanity), and the other applied to that (Humanity).
I started this thread because, if Will is an essence of all life then Determinists are forced into an even more difficult position. You must explain for all types of Causes, to therein correspond to any-and-all types of Freedom, especially that of the simplest organic life, along with the most complex (and evolved).
2. Falsifiability of Free Will
It doesn’t matter if ‘freedom’ is used physically or metaphysically, or even absurdly. If anything can shown to be free, which as you imply is a matter of Ability, then a case is made for free-will. Determinism has no such positive standard. Instead Determinism is a reaction to Free-Will (preceding it). Determinism must claim that nobody-and-nothing is free, and furthermore, any-and-all thoughts of ‘freedom’ conceived by Humanity, is an illusion (compared to what?) or a lie (compared to what?). Because Determinism has no other argument, it will always fall into this state.
The presumption is that “all things are caused, and nothing can be free from All Causality”. But “All Causality” doesn’t really mean anything. Causes aren’t a “thing”. A thing must cause another thing. So to say, “all things are caused”, begs-the-question, as to “Caused by What/Whom?”.
This is why Determinism is strongly Judæo-Christian, or if you want to go further back into the past, a product of Absolute Monarchy/Power. Caused by One Thing (A Creator/The Creator).
Without a religious underpinning, without a thesis or premise, there is no “who or what” caused anything, any event, any phenomenon. So Determinism cannot stand on Nothing. If it does, as somebody like Sil presents it, then it is Un-falsifiable, and therefore, not Scientific.
3. Internal Law
So do the Biological or ‘Human’ internal-laws contradict or waver, in any way from, the so-presumed “Natural Law” from which all things are claimed to be Caused (a priori)? Are humans “exceptional”, exceptions from “The Rules”? How about Gravity? Have humans defied Gravity? In the Pragmatic sense, yes, Humans have traveled outside the Earth’s atmosphere, and so are no longer beholden to the Earthly notion of Gravity. The counter-argument: “But Gravity still exists, as a phenomenon and force, even if humanity travels beyond its cause (Earth), and therefore the Cause still exists”
Here’s the problem. The hypothetical “Causes” of anything are only relevant directly pertaining to a specific setting and environment. If humans were born in a space-ship in zero-gravity light-years outside Earth then they would have little or no concept of “Gravity” and so would deny that such a “Law of Gravity” pertains to them. Different environments, and therefore, different laws.
So Sil would argue here, “but there are Grand Physical Laws for everything”. But this is a weak-argument, because you are then trying backpedal your “Causality” to some ultimate-unifying principle, in order to retain a convincing point (that all things are caused, or worse, caused equally, and futhermore, that there is “only one” type of cause).
4. General theme - Unknown causes
My main points have always been this. If your argument for Determinism rests on “Grand Unifying Physical Theories” then A: you’re probably not being as “Scientific” as you think you are (to Sil), B: you almost certainly, don’t know what you’re talking about, and C: if you admit to “Unknown Causes” then you are always presenting a very weak-argument as to the thesis of Determinism-in-general. Any “Deterministic” argument that were reasonable, would present the causes of such-and-such thing or event, or phenomenon, and then use those patterns of causality to either correlate them to the causes of anything else (Hence, Analogy), or understand the pattern of the cause itself.
Conclusion,
It strikes me as obvious and common sense that, even Physically, a rock is least free. Water is ‘freer’. Air is freer still. And fire is ‘freest’ in its ability to move in all directions, quickly, and seemingly randomly. If there is “freedom” in this physical (or metaphysical) sense, then does it really matter to then say that humans, and organic life, is less-free or more-free, from individual to individual? How else could it be that a rock is least free, and then, so is this person right here. Or fire is “freest”, but then so too, is that person right there freest of human people?
It ought to make sense on the most intuitive level that some people “cannot escape” their heavy, laden, immobile state, but others can. Or that a rock has “no choice at all” (to move), while water, wind, and fire, move freely in ways that solid elements “could never hope to”.
If freedom can be analogized to a physical state, then my position is even better. Determinism doesn’t even matter. Because at some point, causes are unknown. But it is still known, that physically some elements or “chemical compositions” are freer than others, based on motion, and so too, physically some humans are freer than others.
It’s an easy step to make to say that this applies to the mind or soul. If all these premises are accepted, then all the causes that are ‘known’, don’t matter.
Freedom is more inherent than “Determinism”. Because Determinism is based only on what humans or cognizant animals know of. But freedom is not dependent upon the consciousness of any human, or any living creature at all.
I believe my position would be as “pre-Socratic” as you can get…