A CUT-FREE SIMPLE SEQUENT CALCULUS FOR MODAL LOGIC S5
Francesca Poggiolesi · The Review of Symbolic Logic · 2008
In this paper, we present a simple sequent calculus for the modal propositional logic S5. We prove that this sequent calculus is theoremwise equivalent to the Hilbert-style system S5, that it is contraction-free and cut-free, and finally that it is decidable. All results are proved in a purely syntactic way.