Yes, possible does not mean feasible. That’s the brunt of Deutsch’s argument: Without an explanation to guide how we would do it, it will remain infeasible.

In the context of the original article, what I found confusing was that it’s an affront to the principle of what’s possible. That seems a non-starter (are at least something that deserves a significant carve-out in the argument).

Instead, the author concludes, “We worry too much about machine intelligence and not enough about self-reproduction, communication, and control. The next revolution in computing will be signaled by the rise of analog systems over which digital programming no longer has control. Nature’s response to those who believe they can build machines to control everything will be to allow them to build a machine that controls them instead.”

There seems to be a moral in there somewhere, but I can’t see past the bedrock of universal (digital) computing. “Nature’s response” is the universality of computation rooted in physical laws about what’s possible and what’s not.

Hence my confusion. I’d like to get back to reality, but I’m struggling to find my footing in this argument. Thanks for your help.