A General Framework for $$ {FDE}$$ FDE -Based Modal Logics

We develop a general theory of FDE-based modal logics. Our framework takes into account the four-valued nature of FDE by considering four partially defined modal operators corresponding to conditions for verifying and falsifying modal necessity and possibility operators. The theory comes with a uniform characterization for all obtained systems in terms of FDE-style formula-formula sequents. We also develop some correspondence theory and show how Hilbert-style axiom systems can be obtained in appropriate cases. Finally, we outline how different systems from the literature can be expressed in our framework.

     

Disentangling Structural Connectives or Life Without Display Property

Journal of Philosophical Logic - The work is concerned with the so called display property of display logic. The motivation behind it is discussed and challenged. It is shown using one display...