## What is to define truth in Mathematical Logic?

Tarski’s Undefinability Theorem says that arithmetical truth cannot be defined in arithmetic. What is the meaning of “definition”? Is it formal? Answer Yes, it is. According to : TARSKI UNDEFINABILITY THEOREM (1933) : The set #ThN [i.e. the set of Gödel-numbers of sentences true in N] is not definable in N. Here the concept of … Read more