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Well, yah, an infinite number of them exist. I'm curious, though, how many of these principles a la the Halting Problem actually hold if they are excluded?

We take as doctrine that the halting problem is generally undecidable, but I haven't heard anything about any results for the Halting Problem (minus self referential paradoxes). Which is concerning because in practice nobody gives a crap about self referential paradoxes and they very rarely actually arise.



There is Rice's theorem (which is simple extension of Halting Problem and a basic theorem in computability theory), which states that all non-trivial, purely semantic properties of programs are undecidable. For more details, see https://en.wikipedia.org/wiki/Rice%27s_theorem .


Interesting, but...

The Wikipedia article gives 2 proofs for Rice's theorem.

a) As a corollary of Kleene's recursion theorem. This proof seems to rely on quines, and therefore relies on the same principle of self-referential paradox?

b) As a proof by reduction to the halting problem.

I'm not very confident in my interpretation of (a) ...




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