Proof Theory of Modal Logic

Consisting of 15 research papers, this text deals with formal, mechanizable reasoning in modal logics. It brings together various directions in the development of generalized sequent-style proof systems. The first part contains papers which give a description of powerful proof-theoretic methods as applied to the normal modal logic S4. Part II is concerned with a number of generalizations of the standard proof-theoretic formats, while the third part presents new and important results on semantics-based proof systems for modal logic.