Question: would such a simulation be conscious? If not, why not?
1. A human brain has consciousness
2. The device is a perfect digital replica of a human brain
I can't think of any argument that the device does not have consciousness that doesn't either rely on basically magic or lead to other ridiculous conclusions.
Because physicalism implies that the mind is an emergent phenomenon, and because quantum physics is a linear theory, there's simply no place for free will unless you go down some weird/unfalsifiable rabbit holes like the MWI.
So a lot of people prefer to latch onto the idea that there is a soul, because if there wasn't one, then they wouldn't be special anymore.
I don't follow. Quantum mechanics means that physics is stochastic, and only approximates classical determinism in aggregate. Meanwhile, brains seem to operate in a critical state that can be tipped to different phase transitions by small perturbations, so there is potential for a quantum event to influence the brain as a whole in a nondeterministic fashion.
This means that strict physicalism still leaves the door open to our behavior being stochastic rather than deterministic, doesn't it?
So in this view consciousness is better explained as an illusion than as the seat of your will. Because you can't really have a will if every interaction that led to your existence can, in principle, be computed forward in time from the big bang. Physicalists see it as a complex emergent phenomenon akin to a run of Conway's Game of Life that started from a random seed.
Whether that stochasticity amounts to free will is a separate discussion, but it is fairly clear to me that many of our decisions are consequential and AREN'T predetermined. Which at least sounds like free will, or close enough to warrant being treated as such, anyway.
The bigger, more relevant, and testable challenge is premise #2. The gap between this proposed research tool and “a perfect digital replica of a human brain” (and all functionally relevant inputs and outputs from all other systems and organs in the body) is monstrously large. Given that we don’t understand what mechanism(s) consciousness arises from, a model would have to be 100% perfect in basically all aspects for the conclusion to be true.
You would not expect your computer to pee on your desk if you were to simulate kidney function, would you?
If my computer is connected to actuators that opens a pee valve like a brain is, then I expect.
The main point, in think, is that we can't say precisely what consciousness is. Everything definition on that that I can imagine is something that can be replicated in a computer or that relies on belief, like the existence of a soul...
I hope that we have answers for that before the technology that allow us to do that
Sometimes a simulation IS the thing. A simulation of a wall clock IS a functioning clock (e.g. the clock icon on our smartphones). An autopilot that can takeoff, fly, and land an airplane IS a pilot. Chess engines that can beat grandmasters are chess players. A computer simulation of a teacher that can educate students is a teacher. Sometimes these simulations lack some of the capabilities of their human counterparts, and sometimes they far exceed them.
> You would not expect your computer to pee on your desk if you were to simulate kidney function, would you?
You would not reject a computer-controlled dialysis machine as "just a simulation" if you had kidney failure would you?
Except that's not a simulation, that's the actual process of dialysis in action (which we fully understand, contrary to consciousness). And coincidentally, a dialysis machine _does not_ look like a kidney, not even remotely, and any homomorphism one can point to, is such only through a great deal of layers of abstraction. I would totally reject a simulation of a kidney.
We are talking about a computer simulation like a neural network. We detect topological relationships in neurons and we are led to believe or entertain the possibility that all there is to it is such topological description, hence any substrate will do. This is completely arbitrary and leads to all sort of phantasies such as "qualities emerge from quantities" and "a simulation of a brain behaves like a brain". A computer simulation of a kidney won't produce urine just like a simulation of a brain won't produce whatever the brain produces, if anything.
Now, to build on your dialysis machine analogy, if we were to understand how consciousness work, and if we were to understand what relationships it holds with the brain and the body, then I submit that anything artificial we will produce will look like biology.
Nobody can defined what consciousness is in terms that can be experimentally validated. Until that happens not only can the question not be answered, it isn't even a question that makes any sense.
To the point, I have a convincing experience of consciousness and free will — qualia — and I suspect a digital clone of my brain would have a similar experience. Although this question is not testable, I think it's inaccurate to say that it doesn't make sense.
If you can provide a satisfying definition of X it’s very clear