A sequence of decidable finitely axiomatizable intermediate logics with the disjunction property

1974 ◽  
Vol 39 (1) ◽  
pp. 67-78 ◽  
Author(s):  
D. M. Gabbay ◽  
D. H. J. De Jongh
Keyword(s):  
Intuitionistic Logic ◽  
Finite Model ◽  
Ordered Sets ◽  
Disjunction Property ◽  
University Of Illinois ◽  
Finite Model Property ◽  
Intermediate Logics ◽  
Heyting Arithmetic ◽  
Image Position ◽  
System 1

The intuitionistic propositional logic I has the following (disjunction) property.We are interested in extensions of the intuitionistic logic which are both decidable and have the disjunction property. Systems with the disjunction property are known, for example the Kreisel-Putnam system [1] which is I + (∼ϕ → (ψ ∨ α))→ ((∼ϕ→ψ) ∨ (∼ϕ→α)) and Scott's system I + ((∼ ∼ϕ→ϕ)→(ϕ ∨ ∼ϕ))→ (∼∼ϕ ∨ ∼ϕ). It was shown in [3c] that the first system has the finite-model property.In this note we shall construct a sequence of intermediate logics Dn with the following properties:These systems are presented both semantically and syntactically, using the remarkable correspondence between properties of partially ordered sets and axiom schemata of intuitionistic logic. This correspondence, apart from being interesting in itself (for giving geometric meaning to intuitionistic axioms), is also useful in giving independence proofs and obtaining proof theoretic results for intuitionistic systems (see for example, C. Smorynski, Thesis, University of Illinois, 1972, for independence and proof theoretic results in Heyting arithmetic).

The decidability of the Kreisel-Putnam system

1970 ◽  
Vol 35 (3) ◽  
pp. 431-437 ◽  
Author(s):  
Dov M. Gabbay
Keyword(s):  
Intuitionistic Logic ◽  
Propositional Logic ◽  
Finite Model ◽  
Model Property ◽  
Intuitionistic Propositional Logic ◽  
Disjunction Property ◽  
Finite Model Property ◽  
Image Position

The intuitionistic propositional logic I has the following disjunction property This property does not characterize intuitionistic logic. For example Kreisel and Putnam [5] showed that the extension of I with the axiomhas the disjunction property. Another known system with this propery is due to Scott [5], and is obtained by adding to I the following axiom:In the present paper we shall prove, using methods originally introduced by Segerberg [10], that the Kreisel-Putnam logic is decidable. In fact we shall show that it has the finite model property, and since it is finitely axiomatizable, it is decidable by [4]. The decidability of Scott's system was proved by J. G. Anderson in his thesis in 1966.

A note on Mathematics of infinity

1993 ◽  
Vol 58 (4) ◽  
pp. 1195-1200 ◽  
Author(s):  
Erik Palmgren
Keyword(s):  
Intuitionistic Logic ◽  
Type Theory ◽  
Natural Numbers ◽  
Disjunction Property ◽  
Recursive Functions ◽  
Choice Sequence ◽  
Heyting Arithmetic ◽  
Image Position

In the paper Mathematics of infinity, Martin-Löf extends his intuitionistic type theory with fixed “choice sequences”. The simplest, and most important instance, is given by adding the axiomsto the type of natural numbers. Martin-Löf's type theory can be regarded as an extension of Heyting arithmetic (HA). In this note we state and prove Martin-Löf's main result for this choice sequence, in the simpler setting of HA and other arithmetical theories based on intuitionistic logic (Theorem A). We also record some remarkable properties of the resulting systems; in general, these lack the disjunction property and may or may not have the explicit definability property. Moreover, they represent all recursive functions by terms.

MODAL LOGICS OF METRIC SPACES

2014 ◽  
Vol 8 (1) ◽  
pp. 178-191 ◽  
Author(s):  
GURAM BEZHANISHVILI ◽  
DAVID GABELAIA ◽  
JOEL LUCERO-BRYAN
Keyword(s):  
Modal Logic ◽  
Metric Space ◽  
Metric Spaces ◽  
Modal Logics ◽  
Finite Model ◽  
Finite Model Property ◽  
Classic Result ◽  
Topological Closure ◽  
Image Position

AbstractIt is a classic result (McKinsey & Tarski, 1944; Rasiowa & Sikorski, 1963) that if we interpret modal diamond as topological closure, then the modal logic of any dense-in-itself metric space is the well-known modal system S4. In this paper, as a natural follow-up, we study the modal logic of an arbitrary metric space. Our main result establishes that modal logics arising from metric spaces form the following chain which is order-isomorphic (with respect to the ⊃ relation) to the ordinal ω + 3:$S4.Gr{z_1} \supset S4.Gr{z_2} \supset S4.Gr{z_3} \supset \cdots \,S4.Grz \supset S4.1 \supset S4.$It follows that the modal logic of an arbitrary metric space is finitely axiomatizable, has the finite model property, and hence is decidable.

Note on a paper in tense logic

1969 ◽  
Vol 34 (2) ◽  
pp. 215-218 ◽  
Author(s):  
R. A. Bull
Keyword(s):  
Tense Logic ◽  
Finite Model ◽  
Model Property ◽  
Ordered Sets ◽  
Finite Model Property ◽  
Finite Models ◽  
Correct Proof

In [1, §4], my ‘proof’ that GH1 has the finite model property is incorrect; there are considerable obscurities towards the end of §1, particularly on p. 33; and I should have exhibited the finite models for GH1. In §1 of this paper I expand the analysis of the sub-directly irreducible models for GH1 which I give in §1 of [1]. In §2 I give a correct proof that GH1 has the finite model property. In §3 I exhibit these finite models as models on certain ordered sets.

scholarly journals NNIL-formulas revisited: Universal models and finite model property

2020 ◽  
Author(s):  
Julia Ilin ◽  
Dick de Jongh ◽  
Fan Yang
Keyword(s):  
Direct Proof ◽  
Finite Model ◽  
Kripke Models ◽  
Model Property ◽  
Finite Model Property ◽  
Universal Models ◽  
Heyting Arithmetic ◽  
First Results

Abstract NNIL-formulas, introduced by Visser in 1983–1984 in a study of $\varSigma _1$-subsitutions in Heyting arithmetic, are intuitionistic propositional formulas that do not allow nesting of implication to the left. The first results about these formulas were obtained in a paper of 1995 by Visser et al. In particular, it was shown that NNIL-formulas are exactly the formulas preserved under taking submodels of Kripke models. Recently, Bezhanishvili and de Jongh observed that NNIL-formulas are also reflected by the colour-preserving monotonic maps of Kripke models. In the present paper, we first show how this observation leads to the conclusion that NNIL-formulas are preserved by arbitrary substructures not necessarily satisfying the topo-subframe condition. Then, we apply it to construct universal models for NNIL. It follows from the properties of these universal models that NNIL-formulas are also exactly the formulas that are reflected by colour-preserving monotonic maps. By using the method developed in constructing the universal models, we give a new direct proof that the logics axiomatized by NNIL-axioms have the finite model property.

The undecidability of the disjunction property of propositional logics and other related problems

1993 ◽  
Vol 58 (3) ◽  
pp. 967-1002 ◽  
Author(s):  
Alexander Chagrov ◽  
Michael Zakharyaschev
Keyword(s):  
Interpolation Property ◽  
Modus Ponens ◽  
Algorithmic Problem ◽  
Finite Model ◽  
Inference Rules ◽  
Property A ◽  
Disjunction Property ◽  
Intermediate Logics ◽  
First Results ◽  
Finite Set

‘How can we recognize, given axioms and inference rules of a calculus, whether the calculus has such-and-such property?’ A question of this kind arises whenever we deal with a new logic system. For large families of logics, this question may be considered as an algorithmic problem, and a property is called decidable in a given family if there exists an algorithm which is capable of deciding, for a finite axiomatics of a calculus in the family, whether or not it has the property.In the class of intermediate propositional logics, for instance, nontrivial properties such as the tabularity, pretabularity, and interpolation property (Maksimova [1972, 1977]) are decidable. However, for many other important properties—decidability, finite model property, disjunction property, Halldén-completeness, etc.—effective criteria were not found in spite of considerable efforts.In this paper we show that the difficulties in investigating these properties in the classes of intermediate logics and normal modal logics containing S4 are of principal nature, since all of them turn out to be algorithmically undecidable. In other words, there are no algorithms which, given a finite set of axioms of an intermediate or modal calculus, can recognize whether or not it is decidable, Halldén-complete, has the finite model or disjunction property.The first results concerning the undecidability of properties of calculi seem to have been obtained by Linial and Post [1949], who proved the undecidability of the problem of equivalence to classical calculus in the class of all propositional calculi with the same language as the classical one and the two inference rules: modus ponens and substitution. Kuznetsov [1963] generalized this result having proved the undecidability of the problem of equivalence to any fixed intermediate calculus (for instance, to intuitionistic calculus or even the inconsistent one). However, these results will not hold if we confine ourselves only to the class of intermediate logics, though the problem of equivalence to the undecidable intermediate calculus of Shehtman [1978] is clearly undecidable in this class as well.

Skolemization in intermediate logics with the finite model property

2016 ◽  
Vol 24 (3) ◽  
pp. 224-237 ◽  
Author(s):  
Matthias Baaz ◽  
Rosalie Iemhoff
Keyword(s):  
Finite Model ◽  
Model Property ◽  
Finite Model Property ◽  
Intermediate Logics

Fibred semantics and the weaving of logics. Part 1: Modal and intuitionistic logics

1996 ◽  
Vol 61 (4) ◽  
pp. 1057-1120 ◽  
Author(s):  
D. M. Gabbay
Keyword(s):  
Proof Theory ◽  
Finite Model ◽  
Finite Model Property ◽  
The Past ◽  
Combined Logics ◽  
Intermediate Logics ◽  
Combination Of Logics ◽  
Combining Logics ◽  
New System ◽  
Intuitionistic Logics

AbstractThis is Part 1 of a paper on fibred semantics and combination of logics. It aims to present a methodology for combining arbitrary logical systems Li, i ∈ I, to form a new system LI. The methodology ‘fibres’ the semantics i of Li into a semantics for LI, and ‘weaves’ the proof theory (axiomatics) of Li into a proof system of LI. There are various ways of doing this, we distinguish by different names such as ‘fibring’, ‘dovetailing’ etc, yielding different systems, denoted by etc. Once the logics are ‘weaved’, further ‘interaction’ axioms can be geometrically motivated and added, and then systematically studied. The methodology is general and is applied to modal and intuitionistic logics as well as to general algebraic logics. We obtain general results on bulk, in the sense that we develop standard combining techniques and refinements which can be applied to any family of initial logics to obtain further combined logics.The main results of this paper is a construction for combining arbitrary, (possibly not normal) modal or intermediate logics, each complete for a class of (not necessarily frame) Kripke models. We show transfer of recursive axiomatisability, decidability and finite model property.Some results on combining logics (normal modal extensions of K) have recently been introduced by Kracht and Wolter, Goranko and Passy and by Fine and Schurz as well as a multitude of special combined systems existing in the literature of the past 20–30 years. We hope our methodology will help organise the field systematically.

Tense logic for discrete future time

1970 ◽  
Vol 35 (1) ◽  
pp. 105-118 ◽  
Author(s):  
Patrick Schindler
Keyword(s):  
Propositional Calculus ◽  
Tense Logic ◽  
Finite Model ◽  
Logical System ◽  
Model Property ◽  
Future Time ◽  
Finite Model Property ◽  
Complete Basis ◽  
Image Position ◽  
Classical Propositional Calculus

Prior has conjectured that the tense-logical system Gli obtained by adding to a complete basis for the classical propositional calculus the primitive symbol G, the definitionsDf. F: Fα = NGNαDf. L: Lα = KαGα,and the postulatesis complete for the logic of linear, infinite, transitive, discrete future time. In this paper it is demonstrated that that conjecture is correct and it is shown that Gli has the finite model property: see [4]. The techniques used are in part suggested by those used in Bull [2] and [3]:Gli can be shown to be complete for the logic of linear, infinite, transitive, discrete future time in the sense that every formula of Gli which is true of such time can be proved as a theorem of Gli. For this purpose the notion of truth needs to be formalized. This formalization is effected by the construction of a model for linear, infinite, transitive, discrete future time.

scholarly journals TOPOLOGICAL COMPLETENESS OF LOGICS ABOVE S4

2015 ◽  
Vol 80 (2) ◽  
pp. 520-566 ◽  
Author(s):  
GURAM BEZHANISHVILI ◽  
DAVID GABELAIA ◽  
JOEL LUCERO-BRYAN
Keyword(s):  
Modal Logic ◽  
Binary Tree ◽  
Finite Model ◽  
Scott Topology ◽  
Model Property ◽  
Topological Semantics ◽  
Finite Model Property ◽  
Normal Modal Logic ◽  
General Frame ◽  
Image Position

AbstractIt is a celebrated result of McKinsey and Tarski [28] that S4 is the logic of the closure algebra Χ+ over any dense-in-itself separable metrizable space. In particular, S4 is the logic of the closure algebra over the reals R, the rationals Q, or the Cantor space C. By [5], each logic above S4 that has the finite model property is the logic of a subalgebra of Q+, as well as the logic of a subalgebra of C+. This is no longer true for R, and the main result of [5] states that each connected logic above S4 with the finite model property is the logic of a subalgebra of the closure algebra R+.In this paper we extend these results to all logics above S4. Namely, for a normal modal logic L, we prove that the following conditions are equivalent: (i) L is above S4, (ii) L is the logic of a subalgebra of Q+, (iii) L is the logic of a subalgebra of C+. We introduce the concept of a well-connected logic above S4 and prove that the following conditions are equivalent: (i) L is a well-connected logic, (ii) L is the logic of a subalgebra of the closure algebra $\xi _2^ + $ over the infinite binary tree, (iii) L is the logic of a subalgebra of the closure algebra ${\bf{L}}_2^ + $ over the infinite binary tree with limits equipped with the Scott topology. Finally, we prove that a logic L above S4 is connected iff L is the logic of a subalgebra of R+, and transfer our results to the setting of intermediate logics.Proving these general completeness results requires new tools. We introduce the countable general frame property (CGFP) and prove that each normal modal logic has the CGFP. We introduce general topological semantics for S4, which generalizes topological semantics the same way general frame semantics generalizes Kripke semantics. We prove that the categories of descriptive frames for S4 and descriptive spaces are isomorphic. It follows that every logic above S4 is complete with respect to the corresponding class of descriptive spaces. We provide several ways of realizing the infinite binary tree with limits, and prove that when equipped with the Scott topology, it is an interior image of both C and R. Finally, we introduce gluing of general spaces and prove that the space obtained by appropriate gluing involving certain quotients of L2 is an interior image of R.

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