Labelled Non-Classical Logics

The subject of this text is the development and investigation of a framework for the modular and uniform presentation and implementation of non-classical logics, in particular modal and relevance logics. Logics are presented as labelled deduction systems, which are proved to be sound and complete with respect to the corresponding Kripke-style semantics. The text investigates the proof theory of certain systems, and shows them to possess structural properties such as normalization and the subformula property, which are exploited not only to establish advantages and limitations of the book's approach with respect to related ones, but also to give, by means of a substructural analysis, a proof-theoretic method for investigating decidability and complexity of (some of) the logics considered. All the deduction systems in the book have been implemented in the generic theorem prover Isabelle, thus providing a simple and natural environment for interactive proof development.