scholarly journals Undecidability of First-Order Intuitionistic and Modal Logics with Two variables

2005 ◽  
Vol 11 (3) ◽  
pp. 428-438 ◽  
Author(s):  
Roman Kontchakov ◽  
Agi Kurucz ◽  
Michael Zakharyaschev
Keyword(s):  
Modal Logic ◽  
Intuitionistic Logic ◽  
Modal Logics ◽  
Kripke Frame ◽  
Standard Nomenclature ◽  
Quantified Modal Logic ◽  
First Order

AbstractWe prove that the two-variable fragment of first-order intuitionistic logic is undecidable, even without constants and equality. We also show that the two-variable fragment of a quantified modal logic L with expanding first-order domains is undecidable whenever there is a Kripke frame for L with a point having infinitely many successors (such are, in particular, the first-order extensions of practically all standard modal logics like K, K4, GL, S4, S5, K4.1, S4.2, GL.3, etc.). For many quantified modal logics, including those in the standard nomenclature above, even the monadic two-variable fragments turn out to be undecidable.

scholarly journals Canonical formulas via locally finite reducts and generalized dualities

10.29007/hgbj ◽  
2018 ◽  
Author(s):  
Nick Bezhanishvili
Keyword(s):  
Modal Logic ◽  
Intuitionistic Logic ◽  
Algebraic Approach ◽  
Modal Logics ◽  
Substructural Logic ◽  
Locally Finite ◽  
Canonical Formulas

The method of canonical formulas is a powerful tool for investigating intuitionistic and modal logics. In this talk I will discuss an algebraic approach to this method. I will mostly concentrate on the case of intuitionistic logic. But I will also review the case of modal logic and possible generalizations to substructural logic.

scholarly journals REALIZABILITY SEMANTICS FOR QUANTIFIED MODAL LOGIC: GENERALIZING FLAGG’S 1985 CONSTRUCTION

2016 ◽  
Vol 9 (4) ◽  
pp. 752-809 ◽  
Author(s):  
BENJAMIN G. RIN ◽  
SEAN WALSH
Keyword(s):  
Modal Logic ◽  
Graph Model ◽  
Church’S Thesis ◽  
Quantified Modal Logic ◽  
First Order ◽  
Continuity Principle ◽  
Generalized Continuity ◽  
Church's Thesis ◽  
Order Arithmetic ◽  
The Stability

AbstractA semantics for quantified modal logic is presented that is based on Kleene’s notion of realizability. This semantics generalizes Flagg’s 1985 construction of a model of a modal version of Church’s Thesis and first-order arithmetic. While the bulk of the paper is devoted to developing the details of the semantics, to illustrate the scope of this approach, we show that the construction produces (i) a model of a modal version of Church’s Thesis and a variant of a modal set theory due to Goodman and Scedrov, (ii) a model of a modal version of Troelstra’s generalized continuity principle together with a fragment of second-order arithmetic, and (iii) a model based on Scott’s graph model (for the untyped lambda calculus) which witnesses the failure of the stability of nonidentity.

scholarly journals Recursive enumerability and elementary frame definability in predicate modal logic

2019 ◽  
Vol 30 (2) ◽  
pp. 549-560 ◽  
Author(s):  
Mikhail Rybakov ◽  
Dmitry Shkatov
Keyword(s):  
Modal Logic ◽  
Modal Logics ◽  
The Other ◽  
Kripke Semantics ◽  
First Order ◽  
Elementary Class ◽  
Recursive Enumerability ◽  
Kripke Frames ◽  
Recursively Enumerable ◽  
The Relationship

Abstract We investigate the relationship between recursive enumerability and elementary frame definability in first-order predicate modal logic. On one hand, it is well known that every first-order predicate modal logic complete with respect to an elementary class of Kripke frames, i.e. a class of frames definable by a classical first-order formula, is recursively enumerable. On the other, numerous examples are known of predicate modal logics, based on ‘natural’ propositional modal logics with essentially second-order Kripke semantics, that are either not recursively enumerable or Kripke incomplete. This raises the question of whether every Kripke complete, recursively enumerable predicate modal logic can be characterized by an elementary class of Kripke frames. We answer this question in the negative, by constructing a normal predicate modal logic which is Kripke complete, recursively enumerable, but not complete with respect to an elementary class of frames. We also present an example of a normal predicate modal logic that is recursively enumerable, Kripke complete, and not complete with respect to an elementary class of rooted frames, but is complete with respect to an elementary class of frames that are not rooted.

scholarly journals COMPLETENESS OF SECOND-ORDER PROPOSITIONAL S4 AND H IN TOPOLOGICAL SEMANTICS

2018 ◽  
Vol 11 (3) ◽  
pp. 507-518
Author(s):  
PHILIP KREMER
Keyword(s):  
Modal Logic ◽  
Intuitionistic Logic ◽  
Second Order ◽  
Topological Semantics ◽  
First Order ◽  
Propositional Modal Logic ◽  
Propositional Quantifiers ◽  
Modal Logic S4 ◽  
Natural Way

AbstractWe add propositional quantifiers to the propositional modal logic S4 and to the propositional intuitionistic logic H, introducing axiom schemes that are the natural analogs to axiom schemes typically used for first-order quantifiers in classical and intuitionistic logic. We show that the resulting logics are sound and complete for a topological semantics extending, in a natural way, the topological semantics for S4 and for H.

A unified completeness theorem for quantified modal logics

2002 ◽  
Vol 67 (4) ◽  
pp. 1483-1510 ◽  
Author(s):  
Giovanna Corsi
Keyword(s):  
Modal Logic ◽  
Completeness Theorem ◽  
Modal Logics ◽  
General Strategy ◽  
Quantified Modal Logic ◽  
Barcan Formula ◽  
Completeness Theorems

AbstractA general strategy for proving completeness theorems for quantified modal logics is provided. Starting from free quantified modal logic K. with or without identity, extensions obtained either by adding the principle of universal instantiation or the converse of the Barcan formula or the Barcan formula are considered and proved complete in a uniform way. Completeness theorems are also shown for systems with the extended Barcan rule as well as for some quantified extensions of the modal logic B. The incompleteness of Q°.B + BF is also proved.

scholarly journals Constructive interpolation in hybrid logic

2003 ◽  
Vol 68 (2) ◽  
pp. 463-480 ◽  
Author(s):  
Patrick Blackburn ◽  
Maarten Marx
Keyword(s):  
Modal Logic ◽  
Strong Evidence ◽  
Interpolation Property ◽  
Modal Logics ◽  
Hybrid Logic ◽  
Basic Algorithm ◽  
Technical Problems ◽  
First Order ◽  
Elementary Class ◽  
Interpolation Algorithms

AbstractCraig's interpolation lemma (if φ → ψ is valid, then φ → θ and θ → ψ are valid, for θ a formula constructed using only primitive symbols which occur both in φ and ψ) fails for many propositional and first order modal logics. The interpolation property is often regarded as a sign of well-matched syntax and semantics. Hybrid logicians claim that modal logic is missing important syntactic machinery, namely tools for referring to worlds, and that adding such machinery solves many technical problems. The paper presents strong evidence for this claim by defining interpolation algorithms for both propositional and first order hybrid logic. These algorithms produce interpolants for the hybrid logic of every elementary class of frames satisfying the property that a frame is in the class if and only if all its point-generated subframes are in the class. In addition, on the class of all frames, the basic algorithm is conservative: on purely modal input it computes interpolants in which the hybrid syntactic machinery does not occur.

Comments on Robert Goldblatt’s “Fine’s Theorem on First-Order Complete Modal Logics”

2020 ◽  
pp. 482-484
Author(s):  
Kit Fine
Keyword(s):  
Modal Logic ◽  
Modal Logics ◽  
First Order

I am grateful to Robert Goldblatt for his lucid and masterly chapter on “canonicity” in modal logic. The main result of Fine 1975a was that a modal logic being first-order complete (i.e. complete for a first-order class of frames) was sufficient for the logic to be canonical, i.e. for its canonical frames to be frames for the logic. But ideally what one would like is an equivalence. ...

scholarly journals FIRST-ORDER POSSIBILITY MODELS AND FINITARY COMPLETENESS PROOFS

2019 ◽  
Vol 12 (4) ◽  
pp. 637-662
Author(s):  
MATTHEW HARRISON-TRAINOR
Keyword(s):  
Modal Logic ◽  
Possible Worlds ◽  
Canonical Model ◽  
Model Construction ◽  
Completeness Proof ◽  
Quantified Modal Logic ◽  
First Order ◽  
Propositional Modal Logic ◽  
Computable Set ◽  
Order Case

AbstractThis article builds on Humberstone’s idea of defining models of propositional modal logic where total possible worlds are replaced by partial possibilities. We follow a suggestion of Humberstone by introducing possibility models for quantified modal logic. We show that a simple quantified modal logic is sound and complete for our semantics. Although Holliday showed that for many propositional modal logics, it is possible to give a completeness proof using a canonical model construction where every possibility consists of finitely many formulas, we show that this is impossible to do in the first-order case. However, one can still construct a canonical model where every possibility consists of a computable set of formulas and thus still of finitely much information.

scholarly journals Efficient Local Reductions to Basic Modal Logic

2021 ◽  
pp. 76-92
Author(s):  
Fabio Papacchini ◽  
Cláudia Nalon ◽  
Ullrich Hustadt ◽  
Clare Dixon
Keyword(s):  
Normal Form ◽  
Modal Logic ◽  
Modal Logics ◽  
First Order ◽  
Local Reasoning ◽  
Resolution Calculus

AbstractWe present novel reductions of the propositional modal logics "Image missing" , "Image missing" , "Image missing" , "Image missing" and "Image missing" to Separated Normal Form with Sets of Modal Levels. The reductions result in smaller formulae than the well-known reductions by Kracht and allow us to use the local reasoning of the prover "Image missing" to determine the satisfiability of modal formulae in these logics. We show experimentally that the combination of our reductions with the prover "Image missing" performs well when compared with a specialised resolution calculus for these logics and with the b̆uilt-in reductions of the first-order prover SPASS.

scholarly journals Coalescing: Syntactic Abstraction for Reasoning in First-Order Modal Logics

10.29007/cpbz ◽  
2018 ◽  
Author(s):  
Damien Doligez ◽  
Jael Kriener ◽  
Leslie Lamport ◽  
Tomer Libal ◽  
Stephan Merz
Keyword(s):  
Modal Logic ◽  
Modal Logics ◽  
Order Logic ◽  
First Order Logic ◽  
First Order ◽  
Propositional Modal Logic ◽  
Theorem Provers ◽  
Syntactic Abstraction

We present a syntactic abstraction method to reason about first-order modal logics by using theorem provers for standard first-order logic and for propositional modal logic.

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