A Heuristic Proof Procedure for Propositional Logic

Theorem proving is one of the oldest applications which require heuristics to prune the search space. Invertible proof procedures has been the major tool. In this paper, we present a novel and powerful heuristic called $nongshim$ which can be seen as an underlying principle of invertible proof procedures. Using this heuristic, we derive an invertible sequent calculus\cite{Ketonen,Troe} from sequent calculus for propositional logic.