Online research in philosophy

Via the formulas-as-types embedding certain extensions of Heyting Arithmetic can be represented in intuitionistic type theories. In this paper we discuss the embedding of ω-sorted Heyting Arithmetic HA ω into a type theory WL, that can be described as Troelstra's system ML 1 0 with so-called weak Σ-elimination rules. By syntactical means it is proved that a formula is derivable in HA ω if and only if its corresponding type in WL is inhabited. Analogous results are proved for Diller's so-called (...) restricted system and for a type theory based on predicate logic instead of arithmetic. (shrink)

In this paper we discuss an interpretation of intuitionistic type theory in many-sorted arithmetic with so-called conditional application. Via the formulas-as-types correspondence the arithmetical system in turn can be embedded in ML, resulting in a characterization of strong Σ-elimination by an axiom of conditional choice.