
Abstract In this paper, we study the metamathematics of consistent arithmetical theories $T$ (containing $\textsf {I}\varSigma _{1}$); we investigate numerical properties based on proof predicates that depend on numerations of the axioms. Numeral Completeness. For every true (in $\mathbb {N}$) sentence $\vec {Q}\vec {x}.\varphi (\vec {x})$, with $\varphi (\vec {x})$ a $\varSigma _{1}(\textsf {I}\varSigma _1)$-formula, there is a numeration $\tau $ of the axioms of $T$ such that $\textsf {I}\varSigma _1\vdash \vec {Q}\vec {x}. \texttt {Pr}_{\tau }(\ulcorner \varphi (\overset {\text{.} }{\vec {x}})\urcorner )$, where $\texttt {Pr}_{\tau }$ is the provability predicate for the numeration $\tau $. Numeral Consistency. If $T$ is consistent, there is a $\varSigma _{1}(\textsf {I}\varSigma _1)$-numeration $\tau $ of the axioms of $\textsf {I}\varSigma _{1}$ such that $\textsf {I}\varSigma _1\vdash \forall\, x. \texttt {Pr}_{\tau }(\ulcorner \neg \textit {Prf}(\ulcorner \perp \urcorner , \overset {\text{.}}{x})\urcorner )$, where $\textit {Prf}(x,y)$ denotes a $\varDelta _{1}(\textsf {I}\varSigma _1)$-definition of ‘$y$ is a $T$-proof of $x$’. Finitist consistency is addressed by generalizing a result of Artemov: Partial finitism. If $T$ is consistent, there is a primitive recursive function $f$ such that, for all $n\in \mathbb {N}$, $f(n)$ is the code of an $\textsf {I}\varSigma _{1}$-proof of $\neg\, \textit{Prf}(\ulcorner \perp \urcorner ,\overline {n})$. These results are not in conflict with Gödel’s Incompleteness Theorems. Rather, they allow to extend their usual interpretation and show a deep connection to reflections in Hilbert’s last papers of 1931.
finitist consistency, metamathematics, numeral completeness, Mathematical logic and foundations, Computer science, Hilbert's programme
finitist consistency, metamathematics, numeral completeness, Mathematical logic and foundations, Computer science, Hilbert's programme
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