Epistemic logic, skepticism, and non-normal modal logic

1981 ◽  
Vol 40 (1) ◽  
pp. 47-67 ◽  
Author(s):  
P. K. Schotch ◽  
R. E. Jennings
Keyword(s):  
Modal Logic ◽  
Epistemic Logic ◽  
Normal Modal Logic

scholarly journals EVERYONE KNOWS THAT SOMEONE KNOWS: QUANTIFIERS OVER EPISTEMIC AGENTS

2019 ◽  
Vol 12 (2) ◽  
pp. 255-270 ◽  
Author(s):  
PAVEL NAUMOV ◽  
JIA TAO
Keyword(s):  
Modal Logic ◽  
Epistemic Logic ◽  
Possible Worlds ◽  
Completeness Theorem ◽  
Kripke Semantics ◽  
Possible Worlds Semantics ◽  
Distributed Knowledge ◽  
First Order ◽  
Soundness And Completeness ◽  
First Order Modal Logic

AbstractModal logic S5 is commonly viewed as an epistemic logic that captures the most basic properties of knowledge. Kripke proved a completeness theorem for the first-order modal logic S5 with respect to a possible worlds semantics. A multiagent version of the propositional S5 as well as a version of the propositional S5 that describes properties of distributed knowledge in multiagent systems has also been previously studied. This article proposes a version of S5-like epistemic logic of distributed knowledge with quantifiers ranging over the set of agents, and proves its soundness and completeness with respect to a Kripke semantics.

scholarly journals Explicit Non-normal Modal Logic

2021 ◽  
pp. 64-81
Author(s):  
Atefeh Rohani ◽  
Thomas Studer
Keyword(s):  
Modal Logic ◽  
Normal Modal Logic

scholarly journals STABLE MODAL LOGICS

2018 ◽  
Vol 11 (3) ◽  
pp. 436-469 ◽  
Author(s):  
GURAM BEZHANISHVILI ◽  
NICK BEZHANISHVILI ◽  
JULIA ILIN
Keyword(s):  
Modal Logic ◽  
General Concept ◽  
Modal Logics ◽  
Normal Modal Logic ◽  
Superintuitionistic Logics ◽  
Modal Systems

AbstractStable logics are modal logics characterized by a class of frames closed under relation preserving images. These logics admit all filtrations. Since many basic modal systems such as K4 and S4 are not stable, we introduce the more general concept of an M-stable logic, where M is an arbitrary normal modal logic that admits some filtration. Of course, M can be chosen to be K4 or S4. We give several characterizations of M-stable logics. We prove that there are continuum many S4-stable logics and continuum many K4-stable logics between K4 and S4. We axiomatize K4-stable and S4-stable logics by means of stable formulas and discuss the connection between S4-stable logics and stable superintuitionistic logics. We conclude the article with many examples (and nonexamples) of stable, K4-stable, and S4-stable logics and provide their axiomatization in terms of stable rules and formulas.

A cut-free labelled sequent calculus for dynamic epistemic logic

2020 ◽  
Vol 30 (1) ◽  
pp. 321-348
Author(s):  
Shoshin Nomura ◽  
Hiroakira Ono ◽  
Katsuhiko Sano
Keyword(s):  
Modal Logic ◽  
Epistemic Logic ◽  
Sequent Calculus ◽  
Dynamic Epistemic Logic ◽  
Kripke Semantics ◽  
Cut Rule ◽  
Public Announcement ◽  
Public Announcement Logic ◽  
Soundness And Completeness ◽  
Labelled Sequent Calculus

Abstract Dynamic epistemic logic is a logic that is aimed at formally expressing how a person’s knowledge changes. We provide a cut-free labelled sequent calculus ($\textbf{GDEL}$) on the background of existing studies of Hilbert-style axiomatization $\textbf{HDEL}$ of dynamic epistemic logic and labelled calculi for public announcement logic. We first show that the $cut$ rule is admissible in $\textbf{GDEL}$ and show that $\textbf{GDEL}$ is sound and complete for Kripke semantics. Moreover, we show that the basis of $\textbf{GDEL}$ is extended from modal logic K to other familiar modal logics including S5 with keeping the admissibility of cut, soundness and completeness.

scholarly journals POSITIVE LOGIC WITH ADJOINT MODALITIES: PROOF THEORY, SEMANTICS, AND REASONING ABOUT INFORMATION

2010 ◽  
Vol 3 (3) ◽  
pp. 351-373 ◽  
Author(s):  
MEHRNOOSH SADRZADEH ◽  
ROY DYCKHOFF
Keyword(s):  
Modal Logic ◽  
Multiagent Systems ◽  
Epistemic Logic ◽  
Proof Theory ◽  
Sequent Calculus ◽  
Dynamic Epistemic Logic ◽  
Algebraic Semantics ◽  
Sequent Calculi ◽  
Closure Operators ◽  
Positive Logic

We consider a simple modal logic whose nonmodal part has conjunction and disjunction as connectives and whose modalities come in adjoint pairs, but are not in general closure operators. Despite absence of negation and implication, and of axioms corresponding to the characteristic axioms of (e.g.) T, S4, and S5, such logics are useful, as shown in previous work by Baltag, Coecke, and the first author, for encoding and reasoning about information and misinformation in multiagent systems. For the propositional-only fragment of such a dynamic epistemic logic, we present an algebraic semantics, using lattices with agent-indexed families of adjoint pairs of operators, and a cut-free sequent calculus. The calculus exploits operators on sequents, in the style of “nested” or “tree-sequent” calculi; cut-admissibility is shown by constructive syntactic methods. The applicability of the logic is illustrated by reasoning about the muddy children puzzle, for which the calculus is augmented with extra rules to express the facts of the muddy children scenario.

MAKING SOME ISSUES OF IMPLICIT KNOWLEDGE EXPLICIT

1992 ◽  
Vol 03 (02) ◽  
pp. 193-223 ◽  
Author(s):  
W. VAN DER HOEK ◽  
J.-J. CH. MEYER
Keyword(s):  
Modal Logic ◽  
Epistemic Logic ◽  
Implicit Knowledge ◽  
Kripke Structures

We discuss issues of expressibility and completeness of the logic of implicit knowledge (I) and “everybody’s knowledge” (E), as introduced in a system with a number m of epistemic agents by Halpern & Moses. The operator E is defined as a conjunction and corresponds semantically to the union of the m accessibility relations. Dually, the operator I is semantically associated with an intersection, but it is, surprisingly, not equivalent with a disjunction. From the view of Kripke structures there is a related asymmetry: although union can be modally defined, intersection cannot! We discuss consequences (in terms of (in)expressibility, correspondence and completeness) of this property for the epistemic logic under consideration and also present an extension of modal logic in which intersection is expressible.

scholarly journals Towards a Logic for Reasoning About Learning in a Changing World

10.29007/8g5j ◽  
2018 ◽  
Author(s):  
Prakash Panangaden ◽  
Mehrnoosh Sadrzadeh
Keyword(s):  
Modal Logic ◽  
Epistemic Logic ◽  
Information Acquisition ◽  
Robot Navigation ◽  
Dynamic Epistemic Logic ◽  
The State ◽  
Changing World

We develop an algebraic modal logic that combines epistemic and dynamic modalities with a view to modelling information acquisition (learning) by automated agents in a changing world. Unlike most treatments of dynamic epistemic logic, we have transitions that ``change the state'' of the underlying system and not just the state of knowledge of the agents. The key novel feature that emerges is the need to have a way of ``inverting transitions'' and distinguishing between transitions that ``really happen'' and transitions that are possible.Our approach is algebraic, rather than being based on a Kripke-style semantics. The semantics are given in terms of quantales. We introduce a class of quantales with the appropriate inverse operations and use it to model toy robot-navigation problems, which illustrate how an agent learns information by taking actions. We discuss how a sound and complete logic of the algebra may be obtained from the positive fragment of PDL with converse.

Infinitary propositional normal modal logic

Studia Logica ◽  
1987 ◽  
Vol 46 (4) ◽  
pp. 291-309 ◽  
Author(s):  
Slavian Radev
Keyword(s):  
Modal Logic ◽  
Normal Modal Logic
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