Cut-elimination for simple type theory with an axiom of choice

1999 ◽  
Vol 64 (2) ◽  
pp. 479-485 ◽  
Author(s):  
G. Mints
Keyword(s):  
Classical Logic ◽  
Type Theory ◽  
Axiom Of Choice ◽  
Second Order ◽  
Cut Elimination ◽  
Simple Type ◽  
Simple Type Theory

AbstractWe present a cut-elimination proof for simple type theory with an axiom of choice formulated in the language with an epsilon-symbol. The proof is modeled after Takahashi's proof of cut-elimination for simple type theory with extensionality. The same proof works when types are restricted, for example for second-order classical logic with an axiom of choice.

A proof of the cut-elimination theorem in simple type theory

1973 ◽  
Vol 38 (2) ◽  
pp. 215-226
Author(s):  
Satoko Titani
Keyword(s):  
Boolean Algebra ◽  
Type Theory ◽  
Arbitrary Number ◽  
Formal System ◽  
Cut Elimination ◽  
Simple Type ◽  
Inductive Definition ◽  
Simple Type Theory ◽  
Maximal Ideals ◽  
Definition Of

In [4], I introduced a quasi-Boolean algebra, and showed that in a formal system of simple type theory, from which the cut rule is omitted, wffs form a quasi-Boolean algebra, and that the cut-elimination theorem can be formulated in algebraic language. In this paper we use the result of [4] to prove the cut-elimination theorem in simple type theory. The theorem was proved by M. Takahashi [2] in 1967 by using the concept of Schütte's semivaluation. We use maximal ideals of a quasi-Boolean algebra instead of semivaluations.The logical system we are concerned with is a modification of Schütte's formal system of simple type theory in [1] into Gentzen style.Inductive definition of types.0 and 1 are types.If τ1, …, τn are types, then (τ1, …, τn) is a type.Basic symbols.a1τ, a2τ, … for free variables of type τ.x1τ, x2τ, … for bound variables of type τ.An arbitrary number of constants of certain types.An arbitrary number of function symbols with certain argument places.

scholarly journals Proof normalization modulo

2003 ◽  
Vol 68 (4) ◽  
pp. 1289-1316 ◽  
Author(s):  
Gilles Dowek ◽  
Benjamin Werner
Keyword(s):  
Type Theory ◽  
Cut Elimination ◽  
Simple Type ◽  
First Order ◽  
Simple Type Theory

AbstractWe define a generic notion of cut that applies to many first-order theories. We prove a generic cut elimination theorem showing that the cut elimination property holds for all theories having a so-called pre-model. As a corollary, we retrieve cut elimination for several axiomatic theories, including Church's simple type theory.

Stratification and cut-elimination

1991 ◽  
Vol 56 (1) ◽  
pp. 213-226 ◽  
Author(s):  
Marcel Crabbé
Keyword(s):  
Set Theory ◽  
Type Theory ◽  
Cut Elimination ◽  
Simple Type ◽  
First Order ◽  
Similar Reason ◽  
Separation Axioms ◽  
Simple Type Theory ◽  
Order Language ◽  
The Universe

In this paper, we show the normalization of proofs of NF (Quine's New Foundations; see [15]) minus extensionality. This system, called SF (Stratified Foundations) differs in many respects from the associated system of simple type theory. It is written in a first order language and not in a multi-sorted one, and the formulas need not be stratifiable, except in the instances of the comprehension scheme. There is a universal set, but, for a similar reason as in type theory, the paradoxical sets cannot be formed.It is not immediately apparent, however, that SF is essentially richer than type theory. But it follows from Specker's celebrated result (see [16] and [4]) that the stratifiable formula (extensionality → the universe is not well-orderable) is a theorem of SF.It is known (see [11]) that this set theory is consistent, though the consistency of NF is still an open problem.The connections between consistency and cut-elimination are rather loose. Cut-elimination generally implies consistency. But the converse is not true. In the case of set theory, for example, ZF-like systems, though consistent, cannot be freed of cuts because the separation axioms allow the formation of sets from unstratifiable formulas. There are nevertheless interesting partial results obtained when restrictions are imposed on the removable cuts (see [1] and [9]). The systems with stratifiable comprehension are the only known set-theoretic systems that enjoy full cut-elimination.

scholarly journals Natural deduction via graphs: formal definition and computation rules

2007 ◽  
Vol 17 (3) ◽  
pp. 485-526 ◽  
Author(s):  
HERMAN GEUVERS ◽  
IRIS LOEB
Keyword(s):  
Type Theory ◽  
Natural Deduction ◽  
Linear Logic ◽  
Cut Elimination ◽  
Simple Type ◽  
Slight Variation ◽  
Formal Definition ◽  
Simple Type Theory ◽  
Proof Nets ◽  
Definition Of

In this paper, we introduce the formalism of deduction graphs as a generalisation of both Gentzen–Prawitz style natural deduction and Fitch style flag deduction. The advantage of this formalism is that, as with flag deductions (but not natural deduction), subproofs can be shared, but the linearisation used in flag deductions is avoided. Our deduction graphs have both nodes and boxes, which are collections of nodes that also form a node themselves. This is reminiscent of the bigraphs of Milner, where the link graph describes the nodes and edges and the place graph describes the nesting of nodes. We give a precise definition of deduction graphs, together with some illustrative examples. Furthermore, we analyse their computational behaviour by studying the process of cut-elimination and by defining translations from deduction graphs to simply typed lambda terms. From a slight variation of this translation, we conclude that the process of cut-elimination is strongly normalising. The translation to simple type theory removes quite a lot of structure, so we also propose a translation to a context calculus with lets that faithfully captures the structure of deduction graphs. The proof nets of linear logic also offer a graph-like presentation of natural deduction, and we point out some similarities between the two formalisms.

Hauptsatz for higher order logic

1968 ◽  
Vol 33 (3) ◽  
pp. 452-457 ◽  
Author(s):  
Dag Prawitz
Keyword(s):  
Finite Type ◽  
Type Theory ◽  
Predicate Logic ◽  
Higher Order ◽  
Second Order ◽  
Order Logic ◽  
Simple Type ◽  
Higher Order Logic ◽  
Simple Type Theory ◽  
Second Order Logic

I shall prove in this paper that Gentzen's Hauptsatz is extendible to simple type theory, i.e., to the predicate logic obtained by admitting quantification over predicates of arbitrary finite type and generalizing the second order quantification rules to cover quantifiers of other types. (That Gentzen's Hauptsatz is extendible to this logic has been known as Takeuti's conjecture; see [4].) Gentzen's Hauptsatz has been extended to second order logic in a recent paper by Tait [3]. However, as remarked by Tait, his proof seems not to be extendible to higher orders. The present proof is rather an extension of a different proof of the Hauptsatz for second order logic that I have presented in [1].

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