This chapter introduces a simplified, analytic version of sequent calculus K for classical propositional logic CPL. Sections 1.2–1.7 contain the basic material, including a presentation of essential features and techniques of K. In particular, we discuss the construction of proofs and derivations, the problem of derivable and admissible rules, decision procedures and two proofs of completeness.
... [Show full abstract] In sections 1.8–1.11 we introduce the cut rule, one of the most important rules in the framework of sequent calculi. We prove its admissibility in K and discuss several advantages of its application, including the strong completeness proof and the interpolation theorem.