Incompleteness for stably computable formal systems
Abstract
We prove, for stably computably enumerable formal systems, direct analogues of the first and second incompleteness theorems of G\"odel. A typical stably computably enumerable set is the set of Diophantine equations with no integer solutions, and in particular such sets are generally not computably enumerable. And so this gives the first extension of the second incompleteness theorem to non classically computable formal systems. Let's motivate this with a somewhat physical application. Let be the suitable infinite time limit (stabilization in the sense of the paper) of the mathematical output of humanity, specializing to first order sentences in the language of arithmetic (for simplicity), and understood as a formal system. Suppose that all the relevant physical processes in the formation of are Turing computable. Then as defined may \emph{not} be computably enumerable, but it is stably computably enumerable. Thus, the classical G\"odel disjunction applied to is meaningless, but applying our incompleteness theorems to we then get a sharper version of G\"odel's disjunction: assume then either is not stably computably enumerable or is not 1-consistent (in particular is not sound) or cannot prove a certain true statement of arithmetic (and cannot disprove it if in addition is 2-consistent).
Cite
@article{arxiv.2208.04752,
title = {Incompleteness for stably computable formal systems},
author = {Yasha Savelyev},
journal= {arXiv preprint arXiv:2208.04752},
year = {2024}
}
Comments
The framework currently has gaps, this is to be fixed in an upcoming: "Incompleteness theorems via Turing category"