A mathematical theory of truth and an application to the regress problem

Abstract: In this paper a class of languages which are formal enough for mathematical reasoning is introduced. First-order formal languages containing natural numbers and numerals belong to that class. Its languages are called mathematically agreeable (shortly MA). Languages containing a given MA language L, and being sublanguages of L augmended by a monadic predicate are constructed. A mathematical theory of truth (shortly MTT) is formulated for some of these languages. MTT makes them MA languages which posses their own truth predicates. MTT is shown to conform well with the eight norms presented for theories of truth in 'What Theories of Truth Should be Like (but Cannot be)', by Hannes Leitgeb. MTT is free from infinite regress, providing a proper framework to study the regress problem. Main tools used in proofs are Zermelo-Fraenkel (ZF) set theory and classical logic.