Volume 8, Number 3, 243-249, DOI: 10.1007/BF01297689

Ein Syntaktischer Beweis für die Zulässigkeit der Schnittregel im Kalkül von Schütte für die Intuitionistische Typenlogik

Horst Osswald

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Abstract

In [1] Girard gives a procedure, by which all derivations in the ldquocalculus of natural deductionsrdquo of Prawitz [4] are transformed into normal derivations. Exploiting his idea we give a syntactical proof of the admissibility of the cut rule in Schütte's formal system of intuitionistic type theory. We obtain a normal form theorem but not a normalization theorem. Our ldquoBerechnungsprädikaterdquo are different from the ldquocandidats de reductibiliterdquo of Girard. In the case of second order logic ldquoBerechnungsprädikate für Terme t(O)rdquo are not defined for derivations ending with rO e t(O) which are normalizable, but for finite formula sets Gamma with the property, that GammararrrO e t(O) is derivable without cut.

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