## G. Mints

G. Mints

Deptartment of Philosophy

Stanford University

Stanford

Ca 94305, USA

mints@csli.stanford.edu

### Abstract

Craig interpolation theorem (which holds for intuitionistic logic) implies that the derivability of X,X'->Y' implies existence of an interpolant I in the common language of X and X'->Y' such that both X->I and I,X'->Y' are derivable. For classical logic this extends to X,X'->Y,Y', but for intuitionistic logic there are counterexamples. There is a version true for intuitionistic propositional (but not for predicate) logic, and more complicated version for the predicate case.

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