Formal theories and physical manufacturability are two different things, with no necessary connection with each other. People have been manufacturing tools for thousands of years without having any “formal theory” for them. People were making swords and pots and pans and furniture and carts and chariots long before the concept of “formal theory” had ever been invented. Conversely, one can easily construct formal theories of computers which are formally completely coherent and yet physically impossible to construct (such as Turing machines with oracles, or computers that can execute supertasks).
I’d even question whether formal theories of computation (Turing, Church, etc) were actually that relevant to the development of real world computers. One can imagine an alternate timeline in which computers were developed but theoretical computer science saw far less development as a discipline than in ours. The lack of theoretical development no doubt would have had some practical drawbacks at some point, but they still might have gone a long way without it. I mean, you can do a course in theoretical computer science and have no idea how to actually build a CPU, and conversely you can do a course in computer engineering and actually build a CPU yet have zero idea about what Turing machines or lambda calculus is. The theory actually has far less practical relevance than most theoreticians claim
> The ultimate endpoint of this line of reasoning is complete annihilation of the biosphere and its replacement with factories producing nothing but computers and power plants for shuttling electrons. The people who believe computers are a net positive
A very alarmist take. Personally I am at least open-minded about the possibility of an AI having human-like consciousness/intentionality, at least in theory. But even if we could build such an AI in theory, I’m not sure whether it would be a good idea in practice. And I absolutely am opposed to any proposal to destroy the biological environment and replace it with electronics. Some people may well be purveyors of mind-uploading/simulationist woo, but I’m not. Interesting philosophical speculations but no interest in making them a reality (and I think their actual technological feasibility, if it ever happens at all, is long after we are all dead)