Decidability of admissibility:On a problem by friedman and its solution by rybakov

Rybakov (1984) proved that the admissible rules of IPC are decidable. We give a proof of the same theorem, using the same core idea, but couched in the many notions that have been developed in the mean time. In particular, we illustrate how the argument can be interpreted as using refinements of the notions of exactness and extendibility

The Admissible Rules of BD2 and GSc

The Visser rules form a basis of admissibility for the intuitionistic propositional calculus. We show how one can characterise the existence of covers in certain models, by means of formulae. Through this characterisation, we provide a new proof of the admissibility of a weak form of the Visser rules. Finally, we use this observation, coupled with a description of a generalisation of the disjunction property, to provide a basis of admissibility for the intermediate logics BD2 and GSc

On a Problem of Friedman and its Solution by Rybakov

Rybakov(1984a) proved that the admissible rules of IPC are decidable. We give a proof of the same theorem, using the same core idea, but couched in the many notions that have been developed in the mean time. In particular, we illustrate how the argument can be interpreted as using refinements of the notions of exactness and extendibility

The Admissible Rules of BD2 and GSc

The Visser rules form a basis of admissibility for the intuitionistic propositional calculus. We show how one can characterize the existence of covers in certain models by means of formulae. Through this characterization, we provide a new proof of the admissibility of a weak form of the Visser rules. Finally, we use this observation, coupled with a description of a generalization of the disjunction property, to provide a basis of admissibility for the intermediate logics BD2 and GSc

On a Problem of Friedman and its Solution by Rybakov

Rybakov(1984a) proved that the admissible rules of IPC are decidable. We give a proof of the same theorem, using the same core idea, but couched in the many notions that have been developed in the mean time. In particular, we illustrate how the argument can be interpreted as using refinements of the notions of exactness and extendibility

The Admissible Rules of BD2 and GSc

The Visser rules form a basis of admissibility for the intuitionistic propositional calculus. We show how one can characterise the existence of covers in certain models, by means of formulae. Through this characterisation, we provide a new proof of the admissibility of a weak form of the Visser rules. Finally, we use this observation, coupled with a description of a generalisation of the disjunction property, to provide a basis of admissibility for the intermediate logics BD2 and GSc