This paper is focused on automated reasoning based on classical propositional logic and lattice valued propositional logic LP(X) . A new method of automated reasoning is given, and the soundness and completeness theorems of this method are proved. This paper is focused on an automated reasoning based on classical propositional logic and lattice-valued propositional logic LP (X). A new method of automated reasoning is given, and the soundness and completeness theorems of this method are proved.