Given that brains are fundamentally governed by the same physical laws as everything else, there shouldn't be anything about them which cannot be replicated in some way by something sufficiently capable of emulation of their processes.
That's not to say it's simple. Just that brains obey the laws of physics, and as long as that's true, they should be able to be replicable.
Unless your contention is that brains are somehow able to operate outside the constraints of the laws of physics, in which case we're going to have a fundamental difference of opinion as to the nature of the universe and whether things with brains are particularly special.
We are unable to get two biologically identical (or at least extremely close) brains of identical twins to develop in the same way, let alone two distinct brains, or a simulated version of a brain.
The claim is potentially equivalent to a claim that since universe is theoretically computable, we'll eventually be able to simulate it.
If i take every atom/molecule from one brain (assume a snapshot in time) and replicate it one by one at a different location, and replicate the external IO (stimulus, glucose...), what evidence do we have that this won't work? likely not much
Now instead of replicating ALL the atoms/molecules exactly, I replace one of the higher level entities like a single neuron with a computational equivalent - a tiny computer of sorts that perfectly replaces a neuron within the error bars of the biological neuron. Will this not work? I mean, will it not behave in the same exact way as the original biological brain with consciousness? (We have some evidence that we can replace certain circuits in the brain with man-made equivalents and it continues to work.)
You know where I'm going with this... FindAll, ReplaceAll. Why would it be any different?
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If i had to argue that it wouldn't be the same, here's a quick braindump off the top of my head:
- some entities like neurons literally cannot be replicated without the goo. physics limitation? but the existence of the goo is a proof of existence. but still, maybe the goo has properties that cannot be replicated with other substances
- our model of the physical world has serious limitations. on the order of pre-knowing-speed-of-light-limitation. maybe putting the building blocks together does not create the full thing. maybe building blocks + magic is needed to create the whole.
- other fun limitation of our physical model
Also, we don't have evidence that the processes in the brain are replicable at all, if for example Penrose's theories are correct (or any other non-reductionist that accepts the need for local identity and/or metaphysical properties for the consciousness). You need to assume A LOT of things in order to get this theory some credit, and many things we are literally unable to explain (like consciousness itself) should be reduced to those assumptions in order to make it work (for example, you must assume that is not the gooey stuff that gives rise to the consciousness in the first place, that it does not need very extremely specific conditions to exist, and so on). This line of thinking is kinda dangerous.
> What you really mean is is there any meaningful difference in what can be processed by biological computing and non-biological computing.
> The answer to that would appear to be, no.
> i would rather ask one to think, what evidence is there that we cannot do brain on non-gooey stuff?
I don't think this should stop us from trying, and it's pretty obvious it won't. But there is no proof either way — potentially the problem is so complex that we never get there in practice?
(Also note that proving a general negative statement is pretty tricky and usually avoided — we usually look for counter-examples, evaluate a full finite/countable set of scenarios, etc)