> Unless you believe that the human brain has magical
> properties, it must be possible to simulate its operation
My point was that nobody has any idea how to even get started. Nobody even knows what research to do to find out how to get started.
To clarify: it is not my position that creating artificial intelligence is *ultimately* impossible as such. I'm only saying that nobody has any idea how to do it or what would be involved, so asking an engineer to design it is ridiculous, not to mention grossly unfair to the engineer.
It has also not been shown that the mind is necessarily entirely contained within the brain, but that's really a separate issue. For the purposes of this discussion I am willing to proceed on the premise that the mind may be purely a function of the physical brain and various inputs. (The inputs are known to be rather complicated; for example the endocrine system is not entirely straightforward to simulate; nonetheless, this does not make simulation theoretically impossible, just very difficult.) I am willing to grant this, because it doesn't have any significant impact on my point. I will explain further...
If the mind is a function of purely physical phenomena, primarily the brain, that does NOT imply that we know how to simulate it, because, straightforwardly, we have absolutely no idea how those physical phenomena work, particularly the brain. If we did have such information, we could easily cure Alzheimer's and any number of other conditions and probably could start to work on the mortality problem itself (by transferring the consciousness from the original brain to some other physical housing; after all, if you really understand how a design works, you can build your own). But we don't even know how many more decades -- or perhaps even centuries, or even millennia -- of research and study we will need in order to get to that point. We don't know *if* we'll ever figure that stuff out, let alone when. So far, every time some brilliant biologist thinks he has an idea how the brain might work, it turns out to be wrong, or at least entirely inadequate to explain observed phenomena. If you don't count ruling out wrong ideas as progress, we've made basically no progress at all. Okay, sure, we now understand some of the minutia, such as how neurotransmitters convey signals from one neuron to another, but we have absolutely no idea how any of that relates to the whole function of the brain as an organ.
So the problem, "design an artificial intelligence that's smart in the same way as a human mind", is currently an impossible problem for engineers, even if it's not categorically theoretically possible in the absolute sense.
Engineers design based on their understanding of how things work. That's the basic starting point they work from. Otherwise, nothing gets designed -- or, at least, nothing that works as intended. Without this understanding, you're asking the engineers, metaphorically, to make bricks not only without straw but also without mud or clay. It's completely impossible, in every way that matters.