> Perhaps the required ANN size to approximate the AI / AGI function is so huge that it's beyond the number of particles on Earth
Perhaps there's a teapot orbiting Mars. It's unlikely tho. I think a better hypothesis would be that to model a brain (if we knew how) one would need the same order of magnitude of neurons and connections. This is completely unachievable now, and even if it were technically possible nobody has a faintest clue about how to train such a thing. We do not understand _many_ things about how the brain learns (no backprop!), how it retains and retrieves memories, etc, etc. The best studied system is vision, and computer vision does actually work pretty well by now, achieving superhuman results on some tasks. Thus far the most complex brain we've been able to accurately and completely model is not even a brain at all - it's just a handful of neurons of a worm. I took an online course in neuroscience a few years ago hoping to gain some insight for my ANN work. The situation with our understanding of even primitive brains of i.e. rodents is, well, primitive. We also don't really have math to accurately model more than a handful of real, biological spiking neurons - PDEs get way, way too complex for anybody to handle. But one could argue we don't have to: ANNs effectively operate in the frequency domain instead, where magnitude of activation approximates spike train frequency, and timing effects are ignored.
Don't get me wrong, I'm pretty sure if we do achieve real AGI, it likely won't be with anything even remotely like the current tech and science stack. Energy efficiency and compute density is just not sufficient. But I'm also pretty confident that even with the current stack we will be able to, eventually, approximate intelligence closely enough to suit many practical uses that seem completely out of reach today, including even some limited degree of logical inference, and dare I say, cognition.
If only people (including myself) weren't so chickenshit and actually seriously worked on (and funded) this stuff, that could even happen in my lifetime. As things stand right now, people are afraid to touch anything AGI related due mostly to fear of ridicule.
In my comment above I am merely referring to the conjecture that _if_ we had ANNs that are large enough, and _if_ we knew how to structure and train them, there doesn't seem to be anything that would _fundamentally_ prevent them from supporting AGI. Those are very, very massive "ifs" indeed, without even a faintest glimmer of light at the end of the tunnel.