OK, sorry, I assumed you were following the discussion.
I was. Apparently a bit more closely than you were following your own part of it, if I might observe.
Following the discussion does not mean accepting repetitions in previous errors in argument as if they contained no errors.
Suppose we have an artificial brain, that is capable of consciousness, hosted by a computer (such as has been discussed in earlier posts).
Stop.
You may be again assuming your conclusions. I believe you probably are.
If we have an "artificial brain that is capable of consciousness", then we have an object.
When you say that it is "hosted by a computer" then what you're saying is that you have the computer running a sim of it.
In other words, if you have a "pick-up truck that is capable of hauling a half ton load" and it's being "hosted by a computer" then obviously we've got a computer in front of us, not a truck.
The computer can't haul a half ton load. So if we ask it to replace the truck in a physical system, it can't do that, unless we're asking it to do something which both objects can physically accomplish (a small category of tasks, I imagine).
What the real truck can actually do, the computer cannot actually do.
So what you're saying here is that we have a computer that's running.
It happens to be running a simulation of an artificial brain, but unless the
physical output of the
physical actions performed by the computer to do this task also end up mimicking the physical outputs of a brain, then the fact that it's running a sim for someone is irrelevant to whatever we want to do with it with regard to a physical system.
(Remember, the fact that it's even running a sim is undetectable from any examination of the object without some sort of knowledge from outside the object... the nature of the intended target of the simulation is stored in a pattern in someone's brain, it has no effect at all upon the computer in front of us.)
Suppose The sensory inputs and motor outputs of this brain are connected to sensors and effectors on a humanoid mechanical chassis, so that it can sense the external environment and physically respond to it. It sees and hears through cameras and microphones, and it moves using artificial muscles (something like ASIMO).
This is precisely the error I was trying to tell you about.
We must be clear that we don't have a brain here, we have a computer. That's all.
It's true that there's someone somewhere who has set up some of the computer's behavior to mimic the behavior of a human brain in some ways, but since the physical machine itself isn't acting like a physical brain in the real world -- and you can open up the machine and verify that by simple observation -- and in fact there is no way to even deduce the fact that someone is using the machine in that way, because that information is part of someone else's brain state... this fact is irrelevant to the scenario we are considering.
So odd as it may seem, we not only can ignore the intended target of the sim this machine is running, we are obligated to ignore it. It is not part of the system we have available to us. (And cannot even be deduced from all the information in the system, for the same reason you can't physically examine someone and tell if she has a twin.)
But let's assume that what you describe here is the case... the machine accepts physical inputs functionally identical to what a brain accepts (remember, there can be no "logical" inputs to a brain, only physical) and produces physical outputs functionally identical to what a brain emits.
OK, what sort of machine can do that for us?
A machine that is built to run digital simulations for us?
Well, no. The physical inputs and outputs of such a machine are way off. So if the machine we use happens to be running a simulation of something, that won't help us... might not hurt, but won't help.
Obviously, to replace any functioning organ in the body, you need to build a physical replica. It might not look a lot like the original organ -- a peg leg, for example -- or it might be indistinguishable, such as a new organ grown from stem cells. But it will physical do what the original did.
Just like our replacement truck needs to be able to haul 1,000 pounds.
So that's what this machine will have to be, a functional replica.
To do that, we must use the artificial brain we built at the start. The computer running the simulation of the artificial brain cannot be used, because its physical outputs are all wrong.
Through this interactive interface, the conscious entity has learned about the world - or at least, the environment the humanoid machine has access to [it seems to me that if we were able to construct an artificial brain based on the structure and function of the human brain, e.g. multiple neural emulators connected together, that could support consciousness, it would need to develop and learn in a roughly similar way to a human brain before it would be able to understand its environment and communicate effectively].
Now, as long as we're talking about putting the artificial brain into this mix with other machinery, we're good.
If you're talking about using a machine that's built for another task (like running a simulation or browsing the internet or mixing records) then it won't work.
And btw, I was being generous when we talked about replacing the neurons.
If trans-brain waves are indeed part of the solution to the puzzle of consciousness (and they're our best candidates for generating anything that's coordinated across disparate brain areas, which we know is happening) then replacing them with another material might screw that up.
It could be that our rebuilt bit of cortex ends up creating a conscious blind spot.
It's this sort of thing that we have to be very careful about.
At first glance, you might think you could represent power lines pretty easily as input/output, for example. But you can't. Something as simple as arranging them vertically or in triangular arrangements makes a huge difference in how they behave.
As always, shape matters.
So anyway, no, like I said from the beginning, you can't take something imaginary (like the intended target of a computer simulation) and replace a real part with it.
Are you following?