Abstract
The paper presents a family of propositional epistemic logics such that languages of these logics are extended by quantification over modal (epistemic) operators or over agents of knowledge and extended by predicate symbols that take modal (epistemic) operators (or agents) as arguments. Denote this family by \({\mathcal {P}\mathcal {E}\mathcal {L}}_{({ QK})}\). There exist epistemic logics whose languages have the above mentioned properties (see, for example Corsi and Orlandelli in Stud Log 101:1159–1183, 2013; Fitting et al. in Stud Log 69:133–169, 2001; Grove in Artif Intell 74(2):311–350, 1995; Lomuscio and Colombetti in Proceedings of ATAL 1996. Lecture Notes in Computer Science (LNCS), vol 1193, pp 71–85, 1996). But these logics are obtained from first-order modal logics, while a logic of \({\mathcal {P}\mathcal {E}\mathcal {L}}_{({ QK})}\) can be regarded as a propositional multi-modal logic whose language includes quantifiers over modal (epistemic) operators and predicate symbols that take modal (epistemic) operators as arguments. Among the logics of \({\mathcal {P}\mathcal {E}\mathcal {L}}_{({ QK})}\) there are logics with a syntactical distinction between two readings of epistemic sentences: de dicto and de re (between ‘knowing that’ and ‘knowing of’). We show the decidability of logics of \({\mathcal {P}\mathcal {E}\mathcal {L}}_{({ QK})}\) with the help of the loosely guarded fragment (LGF) of first-order logic. Namely, we generalize LGF to a higher-order decidable loosely guarded fragment. The latter fragment allows us to construct various decidable propositional epistemic logics with quantification over modal (epistemic) operators. The family of this logics coincides with \({\mathcal {P}\mathcal {E}\mathcal {L}}_{({ QK})}\). There are decidable propositional logics such that these logics implicitly contain quantification over agents of knowledge, but languages of these logics are usual propositional epistemic languages without quantifiers and predicate symbols (see Grove and Halpern in J Log Comput 3(4):345–378, 1993). Some logics of \({\mathcal {P}\mathcal {E}\mathcal {L}}_{({ QK})}\) can be regarded as counterparts of logics defined in Grove and Halpern (J Log Comput 3(4):345–378, 1993). We prove that the satisfiability problem for these logics of \({\mathcal {P}\mathcal {E}\mathcal {L}}_{({ QK})}\) is Pspace-complete using their counterparts in Grove and Halpern (J Log Comput 3(4):345–378, 1993).
Similar content being viewed by others
References
Andréka, H., J. van Benthem, and I. Németi, Modal Languages and Bounded Fragments of Predicate Logic, Journal of Philosophical Logic 27(3):217–274, 1998.
Blackburn, P., M. de Rijke, and Y. Venema, Modal Logic, Cambridge University press, Cambridge, 2001.
Chagrov, A., and M. Zakharyaschev, Modal Logic, Oxford University press, Oxford, 1997.
Corsi, G., and E. Orlandelli, Free Quantified Epistemic Logics, Studia Logica 101:1159–1183, 2013.
De Giacomo, G., Y. Lespérance, and F. Patrizi, Bounded Epistemic Situation Calculus Theories, in Proceedings of IJCAI, AAAI Press, 2013.
Enderton, H. B., Second-Order and Higher-Order Logic, Stanford Encyclopedia of Philosophy, 2009.
Fagin, R., J. Y. Halpern, Y. Moses, and M. Y. Vardi, Reasoning about Knowledge, The MIT Press, Cambridge, 1995.
Fitting, M., L. Thalmann, and A. Voronkov, Term-Modal Logics, Studia Logica 69:133–169, 2001.
Gabbay, D. M., A. Kurucz, F. Wolter, and M. Zakharyaschev, Many-Dimensional Modal Logic: Theory and Applications, Studies in Logic 148, Elsevier, 2003.
Grädel, E., On the Restraining Power of Guards, Journal of Symbolic Logic 64(4):1719–1742, 1999.
Grove, A. J., and J. Y. Halpern, Naming and Identity in Epistemic Logics. Part I: the Propositional Case, Journal of Logic and Computation 3(4):345–378, 1993.
Grove, A. J., Naming and Identity in Epistemic Logic. Part II: a First-Order Logic for Naming, Artificial Intelligence 74(2):311–350, 1995.
Halpern, J. Y., and Y. Moses, A Guide to the Modal Logics of Knowledge and Belief, in Proceedings of IJCAI 1985, pp. 480–490.
Hodkinson, I., Loosely Guarded Fragment of First-Order Logic Has the Finite Model Property, Studia Logica 70(2):205–240, 2002.
Kieroński, E., Results on the Guarded Fragment with Equivalence or Transitive Relations, Proceedings of CSL 2005. Lecture Notes in Computer Science (LNCS) vol. 3634, 2005, pp. 309–324.
Kokorin, A. I., and A. G. Pinus, Decidability Problems of Extended Theories, Russian Math. Surveys 33(2):53–96, 1978.
Lakemeyer, G., and H. J. Levesque, Decidable Reasoning in a Fragment of the Epistemic Situation Calculus, in C. Baral, G. De Giacomo, and T. Eiter (eds.), Proceedings of KR, AAAI Press, 2014.
Larsson, S., The Magic of Negative Introspection, Ursus Philosophicus - Essays dedicated to Björn Haglund on his sixtieth birthday. Philosophical Communications, Web Series, No. 32:132–136, Dept. of Philosophy, Göteborg University, Sweden, 2004.
Lomuscio, A., and M. Colombetti, QLB: a Quantified Logic for Belief, in J. Müller, M. Wooldridge, and N. Jennings (eds.), Proceedings of ATAL 1996. Lecture Notes in Computer Science (LNCS) vol. 1193, 1996, pp. 71–85.
Meyer, J.-J. Ch., and W. van der Hoek, Epistemic Logic for AI and Computer Science, Cambridge University Press, Cambridge, 1995.
Shapiro, S., Foundations without Foundationalism. A Case for Second-Order Logic, Oxford University Press, Oxford, 1991.
van Benthem, J., Dynamic Bits and Pieces, Technical Report LP-97-01, Institute for Logic, Language and Computation, University of Amsterdam, 1997.
van Benthem, J., and K. Doets, Higher-Order Logic, in D. M. Gabbay, and F. Guenthner (eds.), Handbook of Philosophical Logic, 2nd edition, vol. 1, Kluwer, Dordrecht, 2001, pp. 189–244.
van Ditmarsch, H., J. Y. Halpern, W. van der Hoek, and B. Kooi, An Introduction to Logics of Knowledge and Belief, in Handbook of Epistemic Logic, College Publications, London, 2015, pp. 1–51.
Wolter, F., and M. Zakharyaschev, Decidable Fragments of First-Order Modal Logics, Journal of Symbolic Logic 66(3):1415–1438, 2001.
Acknowledgements
I am grateful to my teacher, Prof. Alexander Chagrov, for numerous discussions that have significantly influenced on the results and the style of the article. I would also like to express my appreciation for the time and effort of three referees, whose comments and criticism were extremely helpful.
Author information
Authors and Affiliations
Corresponding author
Additional information
Dedicated to the Memory of My Teacher, Alexander Chagrov.
Rights and permissions
About this article
Cite this article
Shtakser, G. Propositional Epistemic Logics with Quantification Over Agents of Knowledge. Stud Logica 106, 311–344 (2018). https://doi.org/10.1007/s11225-017-9741-0
Received:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11225-017-9741-0