Predictabilty hasn't anything to do with freedom either.

it should then follow that a perfect computer model of someone's brain would make the exact same decisions as that person

So what?

In other words, we don't actually make any decisions for ourselves. It's all determined by chemistry.

Nonsense. We are the chemistry, we are our brains. Are we "determined" by ourselves?

the fact they shot their wife was actually nothing they could have had any control over, and it's very unfair to lock them away for 30 years

That comes from the ancient and barbaric conception of penal justice as retribution. Punishment is a disincentive and the very right thing to do to prevent crime.

Edit: also that's again the faked duality. "...nothing they could have any control over" as if the subject is a pure soul completely apart from the universe and its forces. The subject is part of the universe, exactly the part of the universe that could have any control over killing or not killing. We put that part of the universe behind bars to prevent it from killing again and sending a message to other parts of the universe that could feel tempted to do the same. Also, in theory, to try to modify that part of the universe so it wont kill again.

But this isn't even deterministic on its own terms. Particle decay is stochastic. Quantum tunneling is stochastic. There's a constant, silent rain of neutrinos that don't interact nearly all the time.

Fully deterministic analog electronic computing is impossible because we cannot eliminate Johnson noise and shot noise. Why do people then think that neural computing would be noise-free?

>The theory goes that, on an atomic level, interactions between particles is a deterministic process - it's wholly and completely predictable because the outcome is determined by a knowable set of rules. Given the fact that our brains are just[1] a huge set of particles and chemical processes it should then follow that a perfect computer model of someone's brain would make the exact same decisions as that person.

yes. Absolutely true. In theory. The coin head/tail outcome can be modeled and predicted even more easily than brain. Thus the coin is an example of determinism. In theory. On practice though it is the thing that comes among firsts to mind when we talk about in-determinism.

Giving the amount of computations necessary to perfectly model even a coin, less a brain, and the minimum energy cost of a unit of computation, it may be so that such perfect computer is just not possible inside our Universe (it may happen that Universe is the smallest computer that can run such simulation and that exactly that it is doing right now :)

That is not true. The quantum mechanics doesn't disprove determinism, but is clearly states the result can not be predicted, because an act of measurement changes the outcome.

That means it's not magic, but uncertainty that makes exact outcome of a system unpredictable. We can just know probability of the outcome.

Of course this unpredictability doesn't mean there's free will, it just means that we will never be able to find out with a 100% certainty what we will think even if we measured every little detail about the brain.

And if the argument is "But let's imagine we knew every little detail about a brain to atomic level, then we would surely know what he will think in the future" then we are talking about imaginary things. Magic knowledge doesn't exist.

.. which are vastly incomplete, themselves, because we have not reached the limit for where the atoms stop and the particles begin, and even beyond that, there is much evidence that we have not gotten, in fact, to the bottom of things.

>The counter argument requires 'magic' in the form of something that we can control that can't be measured. That's a big ask for any rational scientist.

Good thing rational scientists are willing - pun intended - to continue the investigation and discover just what it is we have not measured, and cannot measure, until we decide to do so.

Can decisions be weighed? Do they have mass, energy, substance? Does a decision exist somewhere in the universe, or is it able to move around the physical universe unhindered by physics? It could be argued that there are no definitive answers to those questions ..

But if the mind (note wording change) were not just atomic particles (that it, God, souls, or some such was involved), when you cut brains up and looked, what would you see?