Formal Definition of Relevant Logical Symbol Occurrence

The formalization of human reasoning is a main issue in artificial intelligence. Although relevant logic is one of most useful ways of such formalization, inference of logic does not correspond to that of human reasoning because the aim of logical inference is to deal with the truth values of propositions while that of human reasoning is to discover useful information. We introduce the concept of logical symbol occurrence relevance into relevant logic for formalization of human reasoning. This paper discusses relevance of logical symbol occurrence and gives formal definition of relevance from the discussion. Moreover, we propose new logic where all logical symbol occurrences in theorems are relevant with respect to the relevance definition of this paper.