Metamathematics of Contexts

In this paper we investigate the simple logical properties of contexts. We describe both the syntax and semantics of a general propositional language of context, and we give a Hilbert style proof system for this language. A proposi-tional logic of context extends classical propositional logic in two ways. Firstly, a new modality, ist(;), is introduced. It is used to express that the sentence, , holds in the context,. Secondly, each context has its own vocabulary, i.e. a set of propositional atoms which are deened or meaningful in that context. The main results of this paper are the soundness and completeness of this Hilbert style proof system. We also provide soundness and completeness results (i.e., correspondence theory) for various extensions of the general system. Finally, we prove that our logic is decidable, and give a brief comparison of our semantics to Kripke semantics.