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  1. Joseph Y. Halpern & Christopher Hitchcock (forthcoming). Graded Causation and Defaults. British Journal for the Philosophy of Science:axt050.
    Recent work in psychology and experimental philosophy has shown that judgments of actual causation are often influenced by consideration of defaults, typicality, and normality. A number of philosophers and computer scientists have also suggested that an appeal to such factors can help deal with problems facing existing accounts of actual causation. This article develops a flexible formal framework for incorporating defaults, typicality, and normality into an account of actual causation. The resulting account takes actual causation to be both graded and (...)
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  2. Joseph Y. Halpern, Rafael Pass & Lior Seeman (2014). Decision Theory with Resource‐Bounded Agents. Topics in Cognitive Science 6 (2):245-257.
    There have been two major lines of research aimed at capturing resource-bounded players in game theory. The first, initiated by Rubinstein (), charges an agent for doing costly computation; the second, initiated by Neyman (), does not charge for computation, but limits the computation that agents can do, typically by modeling agents as finite automata. We review recent work on applying both approaches in the context of decision theory. For the first approach, we take the objects of choice in a (...)
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  3. Joseph Y. Halpern (2013). From Causal Models to Counterfactual Structures. Review of Symbolic Logic 6 (2):305-322.
    Galles & Pearl (l998) claimed that s [possible-worlds] framework.s framework. Recursive models are shown to correspond precisely to a subclass of (possible-world) counterfactual structures. On the other hand, a slight generalization of recursive models, models where all equations have unique solutions, is shown to be incomparable in expressive power to counterfactual structures, despite the fact that the Galles and Pearl arguments should apply to them as well. The problem with the Galles and Pearl argument is identified: an axiom that they (...)
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  4. Joseph Y. Halpern & Christopher Hitchcock (2013). Compact Representations of Extended Causal Models. Cognitive Science 37 (6):986-1010.
    Judea Pearl (2000) was the first to propose a definition of actual causation using causal models. A number of authors have suggested that an adequate account of actual causation must appeal not only to causal structure but also to considerations of normality. In Halpern and Hitchcock (2011), we offer a definition of actual causation using extended causal models, which include information about both causal structure and normality. Extended causal models are potentially very complex. In this study, we show how it (...)
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  5. Michael H. Goldstein, Heidi R. Waterfall, Arnon Lotem, Joseph Y. Halpern, Jennifer A. Schwade, Luca Onnis & Shimon Edelman (2010). General Cognitive Principles for Learning Structure in Time and Space. Trends in Cognitive Sciences 14 (6):249-258.
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  6. Joseph Y. Halpern (2009). Intransitivity and Vagueness - Corrigendum. Review of Symbolic Logic 2 (3):591-591.
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  7. Joseph Y. Halpern & Riccardo Pucella (2009). Evidence with Uncertain Likelihoods. Synthese 171 (1):111 - 133.
    An agent often has a number of hypotheses, and must choose among them based on observations, or outcomes of experiments. Each of these observations can be viewed as providing evidence for or against various hypotheses. All the attempts to formalize this intuition up to now have assumed that associated with each hypothesis h there is a likelihood function μ h , which is a probability measure that intuitively describes how likely each observation is, conditional on h being the correct hypothesis. (...)
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  8. Joseph Y. Halpern, Dov Samet & Ella Segev (2009). Defining Knowledge in Terms of Belief: The Modal Logic Perspective. Review of Symbolic Logic 2 (3):469-487.
    The question of whether knowledge is definable in terms of belief, which has played an important role in epistemology for the last 50 years, is studied here in the framework of epistemic and doxastic logics. Three notions of definability are considered: explicit definability, implicit definability, and reducibility, where explicit definability is equivalent to the combination of implicit definability and reducibility. It is shown that if knowledge satisfies any set of axioms contained in S5, then it cannot be explicitly defined in (...)
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  9. Joseph Y. Halpern, Dov Samet & Ella Segev (2009). On Definability in Multimodal Logic. Review of Symbolic Logic 2 (3):451-468.
    Three notions of definability in multimodal logic are considered. Two are analogous to the notions of explicit definability and implicit definability introduced by Beth in the context of first-order logic. However, while by Beth’s theorem the two types of definability are equivalent for first-order logic, such an equivalence does not hold for multimodal logics. A third notion of definability, reducibility, is introduced; it is shown that in multimodal logics, explicit definability is equivalent to the combination of implicit definability and reducibility. (...)
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  10. Francis C. Chu & Joseph Y. Halpern (2008). Great Expectations. Part I: On the Customizability of Generalized Expected Utility. [REVIEW] Theory and Decision 64 (1):1-36.
    We propose a generalization of expected utility that we call generalized EU (GEU), where a decision maker’s beliefs are represented by plausibility measures and the decision maker’s tastes are represented by general (i.e., not necessarily real-valued) utility functions. We show that every agent, “rational” or not, can be modeled as a GEU maximizer. We then show that we can customize GEU by selectively imposing just the constraints we want. In particular, we show how each of Savage’s postulates corresponds to constraints (...)
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  11. Joseph Y. Halpern (2008). Intransitivity and Vagueness. Review of Symbolic Logic 1 (4):530-547.
    There are many examples in the literature that suggest that indistinguishability is intransitive, despite the fact that the indistinguishability relation is typically taken to be an equivalence relation (and thus transitive). It is shown that if the uncertainty perception and the question of when an agent reports that two things are indistinguishable are both carefully modeled, the problems disappear, and indistinguishability can indeed be taken to be an equivalence relation. Moreover, this model also suggests a logic of vagueness that seems (...)
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  12. Joseph Y. Halpern & Riccardo Pucella (2007). Characterizing and Reasoning About Probabilistic and Non-Probabilistic Expectation. J. Acm 54 (3):15.
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  13. Joseph Y. Halpern & Judea Pearl (2005). Causes and Explanations: A Structural-Model Approach. Part I: Causes. British Journal for the Philosophy of Science 56 (4):843-887.
    Department of Computer Science, University of California, Los Angeles, Los Angeles, CA 90095, USA judea{at}cs.ucla.edu' + u + '@' + d + ''//--> We propose a new definition of actual causes, using structural equations to model counterfactuals. We show that the definition yields a plausible and elegant account of causation that handles well examples which have caused problems for other definitions and resolves major difficulties in the traditional account. Introduction Causal models: a review 2.1 Causal models 2.2 Syntax and semantics (...)
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  14. Joseph Y. Halpern (2003). Reasoning About Uncertainty. Mit Press.
  15. Joseph Y. Halpern & Bruce M. Kapron (2003). Erratum to “Zero-One Laws for Modal Logic” [Ann. Pure Appl. Logic 69 (1994) 157–193]. Annals of Pure and Applied Logic 121 (2-3):281-283.
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  16. Joseph Y. Halpern, Robert Harper, Neil Immerman, Phokion G. Kolaitis, Moshe Y. Vardi & Victor Vianu (2001). On the Unusual Effectiveness of Logic in Computer Science. Bulletin of Symbolic Logic 7 (2):213-236.
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  17. Ronald Fagin, Joseph Y. Halpern, Yoram Moses & Moshe Y. Vardi (1999). Common Knowledge Revisited. Annals of Pure and Applied Logic 96 (1-3):89-105.
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  18. Nir Friedman & Joseph Y. Halpern (1999). Belief Revision: A Critique. [REVIEW] Journal of Logic, Language and Information 8 (4):401-420.
    We examine carefully the rationale underlying the approaches to belief change taken in the literature, and highlight what we view as methodological problems. We argue that to study belief change carefully, we must be quite explicit about the ontology or scenario underlying the belief change process. This is something that has been missing in previous work, with its focus on postulates. Our analysis shows that we must pay particular attention to two issues that have often been taken for granted: the (...)
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  19. Ronald Fagin, Joseph Y. Halpern, Yoram Moses & Moshe Y. Vardi (1997). Reasoning About Knowledge: A Response by the Authors. [REVIEW] Minds and Machines 7 (1):113-113.
  20. Adam J. Grove, Joseph Y. Halpern & Daphne Koller (1996). Asymptotic Conditional Probabilities: The Non-Unary Case. Journal of Symbolic Logic 61 (1):250-276.
    Motivated by problems that arise in computing degrees of belief, we consider the problem of computing asymptotic conditional probabilities for first-order sentences. Given first-order sentences φ and θ, we consider the structures with domain {1,..., N} that satisfy θ, and compute the fraction of them in which φ is true. We then consider what happens to this fraction as N gets large. This extends the work on 0-1 laws that considers the limiting probability of first-order sentences, by considering asymptotic conditional (...)
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  21. Joseph Y. Halpern (1996). Should Knowledge Entail Belief? Journal of Philosophical Logic 25 (5):483 - 494.
    The appropriateness of S5 as a logic of knowledge has been attacked at some length in the philosophical literature. Here one particular attack based on the interplay between knowledge and belief is considered: Suppose that knowledge satisfies S5, belief satisfies KD45, and both the entailment property (knowledge implies belief) and positive certainty (if the agent believes something, she believes she knows it) hold. Then it can be shown that belief reduces to knowledge: it is impossible to have false beliefs. While (...)
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  22. Joseph Y. Halpern & Bruce Kapron (1994). Zero-One Laws for Modal Logic. Annals of Pure and Applied Logic 69 (2-3):157-193.
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  23. Ronald Fagin, Joseph Y. Halpern & Moshe Y. Vardi (1992). What is an Inference Rule? Journal of Symbolic Logic 57 (3):1018-1045.
    What is an inference rule? This question does not have a unique answer. One usually finds two distinct standard answers in the literature; validity inference $(\sigma \vdash_\mathrm{v} \varphi$ if for every substitution $\tau$, the validity of $\tau \lbrack\sigma\rbrack$ entails the validity of $\tau\lbrack\varphi\rbrack)$, and truth inference $(\sigma \vdash_\mathrm{t} \varphi$ if for every substitution $\tau$, the truth of $\tau\lbrack\sigma\rbrack$ entails the truth of $\tau\lbrack\varphi\rbrack)$. In this paper we introduce a general semantic framework that allows us to investigate the notion of inference (...)
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  24. Joseph Y. Halpern (1991). Presburger Arithmetic with Unary Predicates is Π11 Complete. Journal of Symbolic Logic 56 (2):637 - 642.
    We give a simple proof characterizing the complexity of Presburger arithmetic augmented with additional predicates. We show that Presburger arithmetic with additional predicates is Π 1 1 complete. Adding one unary predicate is enough to get Π 1 1 hardness, while adding more predicates (of any arity) does not make the complexity any worse.
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  25. Ronald Fagin & Joseph Y. Halpern (1988). I'm OK If You're OK: On the Notion of Trusting Communication. [REVIEW] Journal of Philosophical Logic 17 (4):329 - 354.
    We consider the issue of what an agent or a processor needs to know in order to know that its messages are true. This may be viewed as a first step to a general theory of cooperative communication in distributed systems. An honest message is one that is known to be true when it is sent (or said). If every message that is sent is honest, then of course every message that is sent is true. Various weaker considerations than honesty (...)
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  26. Joseph Y. Halpern (1988). Review: B. C. Moszkowski, Executing Temporal Logic Programs. [REVIEW] Journal of Symbolic Logic 53 (1):309-309.
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  27. Joseph Y. Halpern & Yoram Moses (1986). Taken by Surprise: The Paradox of the Surprise Test Revisited. [REVIEW] Journal of Philosophical Logic 15 (3):281 - 304.
    A teacher announced to his pupils that on exactly one of the days of the following school week (Monday through Friday) he would give them a test. But it would be a surprise test; on the evening before the test they would not know that the test would take place the next day. One of the brighter students in the class then argued that the teacher could never give them the test. "It can't be Friday," she said, "since in that (...)
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