Undefinability vs. definability of satisfaction and truth (Q2702739)

Undoubtedly, Tarski's theorem on the undefinability of truth is one of the main theorems obtained in logic in the last century. The paper starts with the original formulation of Tarski's theorem including studying the various meanings of the notion of a satisfaction predicate. The problem of definability of the notion of truth, in particular of the notion of truth for the language of Peano arithmetic, is discussed. The author shows that the notion of satisfaction (and truth) for the language of Peano arithmetic can be appropriately defined in a certain weak fragment of second order arithmetic.NEWLINENEWLINEFor the entire collection see [Zbl 0948.00030].