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  1. Logics for Epistemic Programs.Alexandru Baltag & Lawrence S. Moss - 2004 - Synthese 139 (2):165 - 224.
    We construct logical languages which allow one to represent a variety of possible types of changes affecting the information states of agents in a multi-agent setting. We formalize these changes by defining a notion of epistemic program. The languages are two-sorted sets that contain not only sentences but also actions or programs. This is as in dynamic logic, and indeed our languages are not significantly more complicated than dynamic logics. But the semantics is more complicated. In general, the semantics of (...)
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  2.  97
    'Knowable' as 'Known After an Announcement'.Philippe Balbiani, Alexandru Baltag, Hans van Ditmarsch, Andreas Herzig, Tomohiro Hoshi & Tiago de Lima - 2008 - Review of Symbolic Logic 1 (3):305-334.
    Public announcement logic is an extension of multiagent epistemic logic with dynamic operators to model the informational consequences of announcements to the entire group of agents. We propose an extension of public announcement logic with a dynamic modal operator that expresses what is true after any announcement: after which , does it hold that Kφ? We give various semantic results and show completeness for a Hilbert-style axiomatization of this logic. There is a natural generalization to a logic for arbitrary events.
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  3.  38
    A Topological Approach to Full Belief.Alexandru Baltag, Nick Bezhanishvili, Aybüke Özgün & Sonja Smets - 2019 - Journal of Philosophical Logic 48 (2):205-244.
    Stalnaker, 169–199 2006) introduced a combined epistemic-doxastic logic that can formally express a strong concept of belief, a concept of belief as ‘subjective certainty’. In this paper, we provide a topological semantics for belief, in particular, for Stalnaker’s notion of belief defined as ‘epistemic possibility of knowledge’, in terms of the closure of the interior operator on extremally disconnected spaces. This semantics extends the standard topological interpretation of knowledge with a new topological semantics for belief. We prove that the belief (...)
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  4.  85
    The Logic of Justified Belief, Explicit Knowledge, and Conclusive Evidence.Alexandru Baltag, Bryan Renne & Sonja Smets - 2014 - Annals of Pure and Applied Logic 165 (1):49-81.
    We present a complete, decidable logic for reasoning about a notion of completely trustworthy evidence and its relations to justifiable belief and knowledge, as well as to their explicit justifications. This logic makes use of a number of evidence-related notions such as availability, admissibility, and “goodness” of a piece of evidence, and is based on an innovative modification of the Fitting semantics for Artemovʼs Justification Logic designed to preempt Gettier-type counterexamples. We combine this with ideas from belief revision and awareness (...)
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  5.  16
    Dynamic Epistemic Logics of Diffusion and Prediction in Social Networks.Alexandru Baltag, Zoé Christoff, Rasmus K. Rendsvig & Sonja Smets - 2019 - Studia Logica 107 (3):489-531.
    We take a logical approach to threshold models, used to study the diffusion of opinions, new technologies, infections, or behaviors in social networks. Threshold models consist of a network graph of agents connected by a social relationship and a threshold value which regulates the diffusion process. Agents adopt a new behavior/product/opinion when the proportion of their neighbors who have already adopted it meets the threshold. Under this diffusion policy, threshold models develop dynamically towards a guaranteed fixed point. We construct a (...)
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  6. Probabilistic Dynamic Belief Revision.Alexandru Baltag & Sonja Smets - 2008 - Synthese 165 (2):179 - 202.
    We investigate the discrete (finite) case of the Popper–Renyi theory of conditional probability, introducing discrete conditional probabilistic models for knowledge and conditional belief, and comparing them with the more standard plausibility models. We also consider a related notion, that of safe belief, which is a weak (non-negatively introspective) type of “knowledge”. We develop a probabilistic version of this concept (“degree of safety”) and we analyze its role in games. We completely axiomatize the logic of conditional belief, knowledge and safe belief (...)
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  7. Quantum Logic as a Dynamic Logic.Alexandru Baltag & Sonja Smets - 2011 - Synthese 179 (2):285 - 306.
    We address the old question whether a logical understanding of Quantum Mechanics requires abandoning some of the principles of classical logic. Against Putnam and others (Among whom we may count or not E. W. Beth, depending on how we interpret some of his statements), our answer is a clear "no". Philosophically, our argument is based on combining a formal semantic approach, in the spirit of E. W. Beth's proposal of applying Tarski's semantical methods to the analysis of physical theories, with (...)
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  8. Keep 'Hoping' for Rationality: A Solution to the Backward Induction Paradox.Alexandru Baltag, Sonja Smets & Jonathan Alexander Zvesper - 2009 - Synthese 169 (2):301 - 333.
    We formalise a notion of dynamic rationality in terms of a logic of conditional beliefs on (doxastic) plausibility models. Similarly to other epistemic statements (e.g. negations of Moore sentences and of Muddy Children announcements), dynamic rationality changes its meaning after every act of learning, and it may become true after players learn it is false. Applying this to extensive games, we “simulate” the play of a game as a succession of dynamic updates of the original plausibility model: the epistemic situation (...)
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  9. The Dynamic Turn in Quantum Logic.Alexandru Baltag & Sonja Smets - 2012 - Synthese 186 (3):753 - 773.
    In this paper we show how ideas coming from two areas of research in logic can reinforce each other. The first such line of inquiry concerns the "dynamic turn" in logic and especially the formalisms inspired by Propositional Dynamic Logic (PDL); while the second line concerns research into the logical foundations of Quantum Physics, and in particular the area known as Operational Quantum Logic, as developed by Jauch and Piron (Helve Phys Acta 42: 842-848, 1969), Pirón (Foundations of Quantum Physics, (...)
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  10. Causal Agency and Responsibility: A Refinement of STIT Logic.Alexandru Baltag, Ilaria Canavotto & Sonja Smets - 2021 - In Alessandro Giordani & Jacek Malinowski (eds.), Logic in High Definition, Trends in Logical Semantics. Berlin, Germany: pp. 149-176.
    We propose a refinement of STIT logic to make it suitable to model causal agency and responsibility in basic multi-agent scenarios in which agents can interfere with one another. We do this by supplementing STIT semantics, first, with action types and, second, with a relation of opposing between action types. We exploit these novel elements to represent a test for potential causation, based on an intuitive notion of expected result of an action, and two tests for actual causation from the (...)
     
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  11.  83
    Keep Changing Your Beliefs, Aiming for the Truth.Alexandru Baltag & Sonja Smets - 2011 - Erkenntnis 75 (2):255-270.
    We investigate the process of truth-seeking by iterated belief revision with higher-level doxastic information . We elaborate further on the main results in Baltag and Smets (Proceedings of TARK, 2009a , Proceedings of WOLLIC’09 LNAI 5514, 2009b ), applying them to the issue of convergence to truth . We study the conditions under which the belief revision induced by a series of truthful iterated upgrades eventually stabilizes on true beliefs. We give two different conditions ensuring that beliefs converge to “full” (...)
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  12.  29
    Truth-Tracking by Belief Revision.Alexandru Baltag, Nina Gierasimczuk & Sonja Smets - 2019 - Studia Logica 107 (5):917-947.
    We study the learning power of iterated belief revision methods. Successful learning is understood as convergence to correct, i.e., true, beliefs. We focus on the issue of universality: whether or not a particular belief revision method is able to learn everything that in principle is learnable. We provide a general framework for interpreting belief revision policies as learning methods. We focus on three popular cases: conditioning, lexicographic revision, and minimal revision. Our main result is that conditioning and lexicographic revision can (...)
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  13.  26
    A Simple Logic of Functional Dependence.Alexandru Baltag & Johan van Benthem - 2021 - Journal of Philosophical Logic 50 (5):939-1005.
    This paper presents a simple decidable logic of functional dependence LFD, based on an extension of classical propositional logic with dependence atoms plus dependence quantifiers treated as modalities, within the setting of generalized assignment semantics for first order logic. The expressive strength, complete proof calculus and meta-properties of LFD are explored. Various language extensions are presented as well, up to undecidable modal-style logics for independence and dynamic logics of changing dependence models. Finally, more concrete settings for dependence are discussed: continuous (...)
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  14.  25
    Keep ‘Hoping’ for Rationality: A Solution to the Backward Induction Paradox.Alexandru Baltag, Sonja Smets & Jonathan Alexander Zvesper - 2009 - Synthese 169 (2):301-333.
    We formalise a notion of dynamic rationality in terms of a logic of conditional beliefs on plausibility models. Similarly to other epistemic statements, dynamic rationality changes its meaning after every act of learning, and it may become true after players learn it is false. Applying this to extensive games, we "simulate" the play of a game as a succession of dynamic updates of the original plausibility model: the epistemic situation when a given node is reached can be thought of as (...)
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  15. The Logic of Quantum Programs.Alexandru Baltag & Sonja Smets - unknown
    We present a logical calculus for reasoning about information flow in quantum programs. In particular we introduce a dynamic logic that is capable of dealing with quantum measurements, unitary evolutions and entanglements in compound quantum systems. We give a syntax and a relational semantics in which we abstract away from phases and probabilities. We present a sound proof system for this logic, and we show how to characterize by logical means various forms of entanglement (e.g. the Bell states) and various (...)
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  16.  22
    To Know is to Know the Value of Variable.Alexandru Baltag - 2016 - In Lev Beklemishev, Stéphane Demri & András Máté (eds.), Advances in Modal Logic, Volume 11. CSLI Publications. pp. 135-155.
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  17.  5
    Logical Models of Informational Cascades.Alexandru Baltag, Zoé Christoff, Jens Ulrik Hansen & Sonja Smets - 2013 - In Johan Van Benthem & Fenrong Lui (eds.), Logic Across the University: Foundations and Applications. College Publications. pp. 405-432.
    In this paper, we investigate the social herding phenomenon known as informational cascades, in which sequential inter-agent communication might lead to epistemic failures at group level, despite availability of information that should be sufficient to track the truth. We model an example of a cascade, and check the correctness of the individual reasoning of each agent involved, using two alternative logical settings: an existing probabilistic dynamic epistemic logic, and our own novel logic for counting evidence. Based on this analysis, we (...)
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  18.  8
    A Modal Logic for Supervised Learning.Alexandru Baltag, Dazhu Li & Mina Young Pedersen - 2022 - Journal of Logic, Language and Information 31 (2):213-234.
    Formal learning theory formalizes the process of inferring a general result from examples, as in the case of inferring grammars from sentences when learning a language. In this work, we develop a general framework—the supervised learning game—to investigate the interaction between Teacher and Learner. In particular, our proposal highlights several interesting features of the agents: on the one hand, Learner may make mistakes in the learning process, and she may also ignore the potential relation between different hypotheses; on the other (...)
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  19. STS: A Structural Theory of Sets.Alexandru Baltag - 2000 - In Michael Zakharyaschev, Krister Segerberg, Maarten de Rijke & Heinrich Wansing (eds.), Advances in Modal Logic, Volume 2. CSLI Publications. pp. 1-34.
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  20. STS: A Structural Theory of Sets.Alexandru Baltag - 2000 - In Marcus Kracht, Maarten de Rijke, Heinrich Wansing & Michael Zakharyaschev (eds.), Advances in Modal Logic. CSLI Publications. pp. 1-34.
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  21.  5
    Johan van Benthem on Logic and Information Dynamics.Alexandru Baltag & Sonja Smets (eds.) - 2014 - Cham, Switzerland: Springer International Publishing.
    This book illustrates the program of Logical-Informational Dynamics. Rational agents exploit the information available in the world in delicate ways, adopt a wide range of epistemic attitudes, and in that process, constantly change the world itself. Logical-Informational Dynamics is about logical systems putting such activities at center stage, focusing on the events by which we acquire information and change attitudes. Its contributions show many current logics of information and change at work, often in multi-agent settings where social behavior is essential, (...)
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  22.  21
    Compositionality in Context.Dag Westerståhl, Alexandru Baltag & Johan van Benthem - 2021 - In A. Palmigiano & M. Zadrzadeh (eds.), Outstanding Contributions to Logic: Samson Abramsky. Springer.
    Compositionality is a principle used in logic, philosophy, mathematics, linguistics, and computer science for assigning meanings to language expressions in a systematic manner following syntactic construction, thereby allowing for a perspicuous algebraic view of the syntax-semantics interface. Yet the status of the principle remains under debate, with positions ranging from compositionality always being achievable to its having genuine empirical content. This paper attempts to sort out some major issues in all this from a logical perspective. First, we stress the fundamental (...)
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  23.  9
    Beliefs and Evidence in Justification Models.Alexandru Baltag, Virginie Fiutek & Sonja Smets - 2016 - In Lev Beklemishev, Stéphane Demri & András Máté (eds.), Advances in Modal Logic, Volume 11. CSLI Publications. pp. 156-176.
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  24.  9
    Dynamic Epistemic Logic of Diffusion and Prediction in Threshold Models.Alexandru Baltag, Zoé Christoff, Rasmus Kraemmer Rendsvig & Sonja Smets - unknown
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  25.  5
    Tracking Probabilistic Truths: A Logic for Statistical Learning.Alexandru Baltag, Soroush Rafiee Rad & Sonja Smets - 2021 - Synthese 199 (3-4):9041-9087.
    We propose a new model for forming and revising beliefs about unknown probabilities. To go beyond what is known with certainty and represent the agent’s beliefs about probability, we consider a plausibility map, associating to each possible distribution a plausibility ranking. Beliefs are defined as in Belief Revision Theory, in terms of truth in the most plausible worlds. We consider two forms of conditioning or belief update, corresponding to the acquisition of two types of information: learning observable evidence obtained by (...)
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  26.  66
    A Semantic-Modal View on Ramsey's Test.Alexandru Baltag & Sonja Smets - unknown
    We present a semantic analysis of the Ramsey test, pointing out its deep underlying flaw: the tension between the “static” nature of AGM revision (which was originally tailored for revision of only purely ontic beliefs, and can be applied to higher-order beliefs only if given a “backwards-looking” interpretation) and the fact that, semantically speaking, any Ramsey conditional must be a modal operator (more precisely, a dynamic-epistemic one). Thus, a belief about a Ramsey conditional is in fact a higher-order belief, hence (...)
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  27. Logic, Rationality, and Interaction.Alexandru Baltag, Jeremy Seligman & Tomoyuki Yamada (eds.) - 2017 - Springer.
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  28. Logic, Rationality, and Interaction. LORI 2017. Lecture Notes in Computer Science, Vol 10455.Alexandru Baltag, Jeremy Seligman & Tomoyuki Yamada (eds.) - 2017 - Springer.
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  29. Logic, Rationality, and Interaction (LORI 2017, Sapporo, Japan).Alexandru Baltag, Jeremy Seligman & Tomoyuki Yamada (eds.) - 2017 - Springer.
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  30.  29
    Logics of Informational Interactions.Alexandru Baltag & Sonja Smets - 2015 - Journal of Philosophical Logic 44 (6):595-607.
    The pre-eminence of logical dynamics, over a static and purely propositional view of Logic, lies at the core of a new understanding of both formal epistemology and the logical foundations of quantum mechanics. Both areas appear at first sight to be based on purely static propositional formalisms, but in our view their fundamental operators are essentially dynamic in nature. Quantum logic can be best understood as the logic of physically-constrained informational interactions between subsystems of a global physical system. Similarly, epistemic (...)
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  31.  37
    Interpolation and Preservation for Pebble Logics.Alexandru Baltag - 1999 - Journal of Symbolic Logic 64 (2):846-858.
  32. 2003 European Summer Meeting of the Association for Symbolic Logic Logic Colloquim'03.Michael Benedikt, Stevo Todorcevic, Alexandru Baltag, Howard Becker, Matthew Foreman, Jean-Yves Girard, Martin Grohe, Peter T. Johnstone, Simo Knuuttila & Menachem Kojman - 2004 - Bulletin of Symbolic Logic 10 (2).
  33. Alexandru Baltag.Alexandru Baltag - 2008 - In Duncan Pritchard & Vincent Hendricks (eds.), Epistemology: 5 Questions. London: Automatic Press/Vip. pp. 21--37.
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  34.  5
    Interpolation and Preservation for Pebble Logics.Alexandru Baltag - 1999 - Journal of Symbolic Logic 64 (2):846-858.
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