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TRUTH AND FEASIBLE REDUCIBILITY

Published online by Cambridge University Press:  20 September 2019

ALI ENAYAT
Affiliation:
DEPARTMENT OF PHILOSOPHY, LINGUISTICS, AND THEORY OF SCIENCE UNIVERSITY OF GOTHENBURG, BOX 200 405 30 GOTHENBURG, SWEDEN E-mail: ali.enayat@gu.se
MATEUSZ ŁEŁYK
Affiliation:
INSTITUTE OF PHILOSOPHY UNIVERSITY OF WARSAW UL. KRAKOWSKIE PRZEDMIEŚCIE 3 00-927 WARSZAWA, POLAND E-mail: mlelyk@uw.edu.pl
BARTOSZ WCISŁO
Affiliation:
INSTITUTE OF MATHEMATICS, POLISH ACADEMY OF SCIENCES UL. ŚNIADECKICH 8 00-656 WARSZAWA, POLAND E-mail: b.wcislo@impan.pl

Abstract

Let ${\cal T}$ be any of the three canonical truth theories CT (compositional truth without extra induction), FS (Friedman–Sheard truth without extra induction), or KF (Kripke–Feferman truth without extra induction), where the base theory of ${\cal T}$ is PA (Peano arithmetic). We establish the following theorem, which implies that ${\cal T}$ has no more than polynomial speed-up over PA.

Theorem.${\cal T}$is feasibly reducible to PA, in the sense that there is a polynomial time computable function f such that for every${\cal T}$-proof π of an arithmetical sentence ϕ, f (π) is a PA-proof of ϕ.

Type
Articles
Copyright
Copyright © The Association for Symbolic Logic 2019 

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