Reduction of tense logic to modal logic. I

1974 ◽  
Vol 39 (3) ◽  
pp. 549-551 ◽  
Author(s):  
S. K. Thomason
Keyword(s):  
Modal Logic ◽  
Logical Consequence ◽  
Tense Logic ◽  
Kripke Semantics ◽  
Relational Semantics ◽  
Propositional Modal Logic ◽  
Formal Systems ◽  
Unary Operator ◽  
Countable Infinity ◽  
Image Position

It will be shown that propositional tense logic (with the Kripke relational semantics) may be regarded as a fragment of propositional modal logic (again with the Kripke semantics). This paper deals only with model theory. The interpretation of formal systems of tense logic as formal systems of modal logic will be discussed in [6].The languages M and T, of modal and tense logic respectively, each have a countable infinity of propositional variables and the Boolean connectives; in addition, M has the unary operator ⋄ and T has the unary operators F and P. A structure is a pair <W, ≺<, where W is a nonempty set and ≺ is a binary relation on W. An assignment V assigns to each propositional variable p a subset V(p) of W. Then V(α)£ W is defined for all formulas α of M or T by induction:We say that α is valid in <W, ≺>, or <W, ≺>, ⊨ α, if ⊩ (α) = W for every assignment V for <W, ≺>. If Γ is a set of formulas of M [T] and α is a formula of M [T], then α is a logical consequence of Γ, or Γ ⊩ α,if α is valid in every model of Γ i.e., in every structure in which all γ ∈ Γ are valid.

Extremely undecidable sentences

1982 ◽  
Vol 47 (1) ◽  
pp. 191-196 ◽  
Author(s):  
George Boolos
Keyword(s):  
Modal Logic ◽  
The Other ◽  
Propositional Modal Logic ◽  
Image Position

Let ‘ϕ’, ‘χ’, and ‘ψ’ be variables ranging over functions from the sentence letters P0, P1, … Pn, … of (propositional) modal logic to sentences of P(eano) Arithmetic), and for each sentence A of modal logic, inductively define Aϕ by[and similarly for other nonmodal propositional connectives]; andwhere Bew(x) is the standard provability predicate for PA and ⌈F⌉ is the PA numeral for the Gödel number of the formula F of PA. Then for any ϕ, (−□⊥)ϕ = −Bew(⌈⊥⌉), which is the consistency assertion for PA; a sentence S is undecidable in PA iff both and , where ϕ(p0) = S. If ψ(p0) is the undecidable sentence constructed by Gödel, then ⊬PA (−□⊥→ −□p0 & − □ − p0)ψ and ⊢PA(P0 ↔ −□⊥)ψ. However, if ψ(p0) is the undecidable sentence constructed by Rosser, then the situation is the other way around: ⊬PA(P0 ↔ −□⊥)ψ and ⊢PA (−□⊥→ −□−p0 & −□−p0)ψ. We call a sentence S of PA extremely undecidable if for all modal sentences A containing no sentence letter other than p0, if for some ψ, ⊬PAAψ, then ⊬PAAϕ, where ϕ(p0) = S. (So, roughly speaking, a sentence is extremely undecidable if it can be proved to have only those modal-logically characterizable properties that every sentence can be proved to have.) Thus extremely undecidable sentences are undecidable, but neither the Godel nor the Rosser sentence is extremely undecidable. It will follow at once from the main theorem of this paper that there are infinitely many inequivalent extremely undecidable sentences.

S. K. Thomason. Noncompactness in propositional modal logic. The journal of symbolic logic, vol. 37 no. 4 (for 1972, pub. 1973), pp. 716–720. - Kit Fine. An incomplete logic containing S4. Theoria, vol. 40 (1974), pp. 23–29. - S. K. Thomason. An incompleteness theorem in modal logic. Theoria, vol. 40 (1974), pp. 30–34. - Martin Gerson. The inadequacy of the neighbourhood semantics for modal logic. The journal of symbolic logic, vol. 40 (1975), pp. 141–148. - Martin Sebastian Gerson. An extension of S4 complete for the neighbourhood semantics but incomplete for the relational semantics. Studio logica, vol. 34 (1975), pp. 333–342. - Martin Gerson. A neighbourhood frame for T with no equivalent relational frame. Zeitschrift für mathematische Logik und Grundlugen der Mathematik, vol. 22 (1976), pp. 29–34. - V. B. Šehtman. On incomplete propositional logics. Soviet mathematics, vol. 18 (1977), pp. 985–989. (English translation by B. F. Wells of O népolnyh logikah vyskazyvanij, Doklady Akadémii Nauk SSSR, vol. 235 (1977), pp. 542–545.) - J. F. A. K. van Benthem. Two simple incomplete modal logics. Theoria, vol. 44 (1978), pp. 25–37. - J. F. A. K. van Benthem and W. J. Blok. Transitivity follows from Dummett's axiom. Theoria, vol. 44 (1978), pp. 117–118. - J. F. A. K. van Benthem. Syntactic aspects of modal incompleteness theorems. Theoria, vol. 44 (1978), vol. 45 (1979). pp. 63–77.

1983 ◽  
Vol 48 (2) ◽  
pp. 488-495 ◽  
Author(s):  
R. A. Bull
Keyword(s):  
Modal Logic ◽  
English Translation ◽  
Nauk Sssr ◽  
Symbolic Logic ◽  
Relational Semantics ◽  
Akademii Nauk Sssr ◽  
Doklady Akademii Nauk Sssr ◽  
Propositional Modal Logic ◽  
Relational Frame ◽  
Incompleteness Theorems

scholarly journals An algebraic generalization of Kripke structures

2008 ◽  
Vol 145 (3) ◽  
pp. 549-577 ◽  
Author(s):  
SÉRGIO MARCELINO ◽  
PEDRO RESENDE
Keyword(s):  
Modal Logic ◽  
Operator Algebras ◽  
Inverse Semigroups ◽  
Kripke Semantics ◽  
Algebraic Semantics ◽  
Propositional Modal Logic ◽  
Kripke Structures ◽  
Algebraic Generalization ◽  
Foliated Manifolds ◽  
Topological Groupoids

AbstractThe Kripke semantics of classical propositional normal modal logic is made algebraic via an embedding of Kripke structures into the larger class of pointed stably supported quantales. This algebraic semantics subsumes the traditional algebraic semantics based on lattices with unary operators, and it suggests natural interpretations of modal logic, of possible interest in the applications, in structures that arise in geometry and analysis, such as foliated manifolds and operator algebras, via topological groupoids and inverse semigroups. We study completeness properties of the quantale based semantics for the systems K, T, K4, S4 and S5, in particular obtaining an axiomatization for S5 which does not use negation or the modal necessity operator. As additional examples we describe intuitionistic propositional modal logic, the logic of programs PDL and the ramified temporal logic CTL.

A solution to the completeness problem for weakly aggregative modal logic

1995 ◽  
Vol 60 (3) ◽  
pp. 832-842 ◽  
Author(s):  
Peter Apostoli ◽  
Bryson Brown
Keyword(s):  
Modal Logic ◽  
Relational Frame Theory ◽  
Truth Condition ◽  
Frame Theory ◽  
Relational Semantics ◽  
Infinite Hierarchy ◽  
Completeness Problem ◽  
Relational Frame ◽  
Image Position

We are accustomed to regarding K as the weakest modal logic admitting of a relational semantics in the style made popular by Kripke. However, in a series of papers which demonstrates a startling connection between modal logic and the theory of paraconsistent inference, Ray Jennings and Peter Schotch have developed a generalized relational frame theory which articulates an infinite hierarchy of sublogics of K, each expressing a species of “weakly aggregative necessity”. Recall that K is axiomatized, in the presence of N and RM, by the schema of “binary aggregation”For each n ≥ 1, the weakly aggregative modal logic Kn is axiomatized by replacing K with the schema of “n-ary aggregation”which is an n-ary relaxation, or weakening, of K. Note that K1 = K.In [3], the authors claim without proof that Kn is determined by the class of frames F = (W, R), where W is a nonempty set and R is an (n + 1)-ary relation on W, under the generalization of Kriple's truth condition according to which □α is true at a point w in W if and only if α is true at one of x1,…,xn for all x1,…, xn in W such that Rw, x1,…, xn.

Back and forth constructions in modal logic: An interpolation theorem for a family of modal logics

1986 ◽  
Vol 51 (4) ◽  
pp. 969-980 ◽  
Author(s):  
George Weaver ◽  
Jeffrey Welaish
Keyword(s):  
Modal Logic ◽  
Logical Consequence ◽  
Logical Truth ◽  
Interpolation Theorem ◽  
Modal Logics ◽  
Kripke Semantics ◽  
Direct Products ◽  
Possible World ◽  
Relational Systems ◽  
Modal Analogue

The following is a contribution to the abstract study of the model theory of modal logics. Historically, individual modal logics have been specified deductively; and, as a result, it has seemed natural to view modal logics as sets of sentences provable in some deductive system. This proof theoretic view has influenced the abstract study of modal logics. For example, Fine [1975] defines a modal logic to be any set of sentences in the modal language L□ which contains all tautologies, all instances of the schema (□(ϕ ⊃ Ψ) ⊃ (□ϕ ⊃ □Ψ)), and which is closed under modus ponens, necessitation and substitution.Here, however, modal logics are equated with classes of “possible world” interpretations. “Worlds” are taken to be ordered pairs (a, λ), where a is a sentential interpretation and λ is an ordinal. Properties of the accessibility relation are identified with those classes of binary relational systems closed under isomorphisms. The origin of this approach is the study of alternative Kripke semantics for the normal modal logics (cf. Weaver [1973]). It is motivated by the desire that modal logics provide accounts of both logical truth and logical consequence (cf. Corcoran and Weaver [1969]) and the realization that there are alternative Kripke semantics for S4, B and M which give identical accounts of logical truth, but different accounts of logical consequence (cf. Weaver [1973]). It is shown that the Craig interpolation theorem holds for any modal logic which has characteristic modal axioms and whose associated class of binary relational systems is closed under subsystems and finite direct products. The argument uses a back and forth construction to establish a modal analogue of Robinson's theorem. The argument for the interpolation theorem from Robinson's theorem employs modal analogues of the Ehrenfeucht-Fraïssé characterization of elementary equivalence and Hintikka's distributive normal form, and is itself a modal analogue of a first order argument (cf. Weaver [1982]).

Categories and Modalities

2018 ◽  
Author(s):  
Kohei Kishida
Keyword(s):  
Modal Logic ◽  
Category Theory ◽  
Kripke Semantics ◽  
Counterpart Theory ◽  
Stone Duality ◽  
Topological Semantics ◽  
First Order ◽  
Propositional Modal Logic ◽  
First Order Modal Logic

Category theory provides various guiding principles for modal logic and its semantic modeling. In particular, Stone duality, or “syntax-semantics duality”, has been a prominent theme in semantics of modal logic since the early days of modern modal logic. This chapter focuses on duality and a few other categorical principles, and brings to light how they underlie a variety of concepts, constructions, and facts in philosophical applications as well as the model theory of modal logic. In the first half of the chapter, I review the syntax-semantics duality and illustrate some of its functions in Kripke semantics and topological semantics for propositional modal logic. In the second half, taking Kripke’s semantics for quantified modal logic and David Lewis’s counterpart theory as examples, I demonstrate how we can dissect and analyze assumptions behind different semantics for first-order modal logic from a structural and unifying perspective of category theory. (As an example, I give an analysis of the import of the converse Barcan formula that goes farther than just “increasing domains”.) It will be made clear that categorical principles play essential roles behind the interaction between logic, semantics, and ontology, and that category theory provides powerful methods that help us both mathematically and philosophically in the investigation of modal logic.

The McKinsey axiom is not compact

1992 ◽  
Vol 57 (4) ◽  
pp. 1230-1238 ◽  
Author(s):  
Xiaoping Wang
Keyword(s):  
Modal Logic ◽  
Modus Ponens ◽  
Intensional Logic ◽  
Normal System ◽  
Propositional Modal Logic ◽  
Modal Operators ◽  
Transformation Rules ◽  
Image Position ◽  
In The Beginning ◽  
Infinite Set

The canonicity and compactness of the KM system are problems historically important in the development of our understanding of intensional logic (as explained in Goldblatt's paper, The McKinsey axiom is not canonical). The problems, however, were unsolved for years in modal logic. In the beginning of 1990, Goldblatt showed that KM is not canonical in The McKinsey axiom is not canonical. The remaining task is to solve the problem of the compactness of KM. In this paper we present a proof showing that the KM system is not compact.The symbols of the language of propositional modal logic are as follows:1. A denumerably infinite set of sentence letters, for example, {p0, P1, p2, …};2. The Boolean connectives &, ⋁, ¬, →, ↔ and parentheses;3. The modal operators L and M where M is defined as ¬L¬.The formation rules of well-formed propositional modal formulae are the formation rules of formulae in classic propositional logic plus the following rule:If A is a well-formed formula, so is LA.A normal modal system is a set of formulae that contains all tautologies and the formulaand is closed under the following transformation rules:Uniform substitution. If A is a theorem, so is every substitution-instance of A.Modus ponens. If A and A → B are theorems, so is B.Necessitation. If A is a theorem, so is LA.Let L be a normal system. Then a set S of formulae is L-consistent if and only if for any formula B, which is the conjunction of some formulae in S, B is not included in L. A set S of formulae is maximal if and only if for every formula A, S either contains A or contains ¬A. A set S of formulae is maximal L-consistent if and only if it is both maximal and L-consistent.

Modal operators and functional completeness, II

1977 ◽  
Vol 42 (3) ◽  
pp. 391-399 ◽  
Author(s):  
S. K. Thomason
Keyword(s):  
Modal Logic ◽  
Possible Worlds ◽  
Kripke Semantics ◽  
Functional Completeness ◽  
Possible World ◽  
States Of Affairs ◽  
Propositional Modal Logic ◽  
Modal Operators ◽  
Fixed Frame ◽  
State Of Affairs

In the Kripke semantics for propositional modal logic, a frame W = (W, ≺) represents a set of “possible worlds” and a relation of “accessibility” between possible worlds. With respect to a fixed frame W, a proposition is represented by a subset of W (regarded as the set of worlds in which the proposition is true), and an n-ary connective (i.e. a way of forming a new proposition from an ordered n-tuple of given propositions) is represented by a function fw: (P(W))n → P(W). Finally a state of affairs (i.e. a consistent specification whether or not each proposition obtains) is represented by an ultrafilter over W. {To avoid possible confusion, the reader should forget that some people prefer the term “states of affairs” for our “possible worlds”.}In a broader sense, an n-ary connective is represented by an n-ary operatorf = {fw∣ W ∈ Fr}, where Fr is the class of all frames and each fw: (P(W))n → P(W). A connective is modal if it corresponds to a formula of propositional modal logic. A connective C is coherent if whether C(P1,…, Pn) is true in a possible world depends only upon which modal combinations of P1,…,Pn are true in that world. (A modal combination of P1,…,Pn is the result of applying a modal connective to P1,…, Pn.) A connective C is strongly coherent if whether C(P1, …, Pn) obtains in a state of affairs depends only upon which modal combinations of P1,…, Pn obtain in that state of affairs.

Modality and folk psychology

2019 ◽  
Vol 28 (1) ◽  
pp. 19-27
Author(s):  
Ja. O. Petik
Keyword(s):  
Modal Logic ◽  
Brain Activity ◽  
Formal System ◽  
Philosophy Of Logic ◽  
Psychological States ◽  
Formal Systems ◽  
Modern Psychology ◽  
Philosophical Interpretation ◽  
Important Direction

The connection of the modern psychology and formal systems remains an important direction of research. This paper is centered on philosophical problems surrounding relations between mental and logic. Main attention is given to philosophy of logic but certain ideas are introduced that can be incorporated into the practical philosophical logic. The definition and properties of basic modal logic and descending ones which are used in study of mental activity are in view. The defining role of philosophical interpretation of modality for the particular formal system used for research in the field of psychological states of agents is postulated. Different semantics of modal logic are studied. The hypothesis about the connection of research in cognitive psychology (semantics of brain activity) and formal systems connected to research of psychological states is stated.

Reduction of tense logic to modal logic II

Theoria ◽  
2008 ◽  
Vol 41 (3) ◽  
pp. 154-169 ◽  
Author(s):  
S. K. THOMASON
Keyword(s):  
Modal Logic ◽  
Tense Logic
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