John Horty University of Maryland, College Park
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  1. John F. Horty & Trevor J. M. Bench-Capon (2012). A Factor-Based Definition of Precedential Constraint. Artificial Intelligence and Law 20 (2):181-214.
    This paper describes one way in which a precise reason model of precedent could be developed, based on the general idea that courts are constrained to reach a decision that is consistent with the assessment of the balance of reasons made in relevant earlier decisions. The account provided here has the additional advantage of showing how this reason model can be reconciled with the traditional idea that precedential constraint involves rules, as long as these rules are taken to be defeasible. (...)
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  2. Henry Prakken & John Horty (2012). An Appreciation of John Pollock's Work on the Computational Study of Argument. Argument and Computation 3 (1):1 - 19.
    John Pollock (1940?2009) was an influential American philosopher who made important contributions to various fields, including epistemology and cognitive science. In the last 25 years of his life, he also contributed to the computational study of defeasible reasoning and practical cognition in artificial intelligence. He developed one of the first formal systems for argumentation-based inference and he put many issues on the research agenda that are still relevant for the argumentation community today. This paper presents an appreciation of Pollock's work (...)
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  3. John Horty (2011). Rules and Reasons in the Theory of Precedent. Legal Theory 17 (1):1-33.
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  4. John Horty (2007). Defaults with Priorities. Journal of Philosophical Logic 36 (4):367 - 413.
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  5. John Horty (2007). Reasons as Defaults. Philosophers' Imprint 7 (3):1-28.
    The goal of this paper is to frame a theory of reasons--what they are, how they support actions or conclusions--using the tools of default logic. After sketching the basic account of reasons as provided by defaults, I show how it can be elaborated to deal with two more complicated issues: first, situations in which the priority relation among defaults, and so reasons as well, is itself established through default reasoning; second, the treatment of undercutting defeat and exclusionary reasons. Finally, and (...)
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  6. John Horty (2006). Right Actions in Perspective. In Henrik Lagerlund, Sten Lindström & Rysiek Sliwinski (eds.), Modality Matters: Twenty-Five Essays in Honour of Krister Segerberg. Uppsala Philosophical Studies 53. 53.
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  7. John F. Horty (2006). Double Time Reference in the Evaluation of Action. In Henrik Lagerlund, Sten Lindström & Rysiek Sliwinski (eds.), Modality Matters: Twenty-Five Essays in Honour of Krister Segerberg. Uppsala Philosophical Studies 53. 53--205.
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  8. John Horty (2004). The Result Model of Precedent. Legal Theory 10 (1):19-31.
    The result model of precedent holds that a legal precedent controls a fortiori cases—those cases, that is, that are at least as strong for the winning side of the precedent as the precedent case itself. This paper defends the result model against some objections by Larry Alexander, drawing on ideas from the field of Artificial Intelligence and Law in order to define an appropriate strength ordering for cases.
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  9. John F. Horty (2003). Reasoning with Moral Conflicts. Noûs 37 (4):557–605.
    Let us say that a normative conflict is a situation in which an agent ought to perform an action A, and also ought to perform an action B, but in which it is impossible for the agent to perform both A and B. Not all normative conflicts are moral conflicts, of course. It may be that the agent ought to perform the action A for reasons of personal generosity, but ought to perform the action B for reasons of prudence: perhaps (...)
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  10. John Horty (2002). Review of Sven Ove Hansson, The Structure of Values and Norms. [REVIEW] Notre Dame Philosophical Reviews 2002 (6).
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  11. John F. Horty (2001). Argument Construction and Reinstatement in Logics for Defeasible Reasoning. Artificial Intelligence and Law 9 (1):1-28.
    This paper points out some problems with two recent logical systems – one due to Prakken and Sartor, the other due to Kowalski and Toni – designedfor the representation of defeasible arguments in general, but with a specialemphasis on legal reasoning.
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  12. John F. Horty (1996). Agency and Obligation. Synthese 108 (2):269 - 307.
    The purpose of this paper is to explore a new deontic operator for representing what an agent ought to do; the operator is cast against the background of a modal treatment of action developed by Nuel Belnap and Michael Perloff, which itself relies on Arthur Prior's indeterministic tense logic. The analysis developed here of what an agent ought to do is based on a dominance ordering adapted from the decision theoretic study of choice under uncertainty to the present account of (...)
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  13. John F. Horty & Nuel Belnap (1995). The Deliberative Stit: A Study of Action, Omission, Ability, and Obligation. [REVIEW] Journal of Philosophical Logic 24 (6):583 - 644.
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  14. John F. Horty (1994). Moral Dilemmas and Nonmonotonic Logic. Journal of Philosophical Logic 23 (1):35 - 65.
    From a philosophical standpoint, the work presented here is based on van Fraassen [26]. The bulk of that paper is organized around a series of arguments against the assumption, built into standard deontic logic, that moral dilemmas are impossible; and van Fraassen only briefly sketches his alternative approach. His paper ends with the conclusion that “the problem of possibly irresolvable moral conflict reveals serious flaws in the philosophical and semantic foundations of ‘orthodox’ deontic logic, but also suggests a rich set (...)
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  15. John F. Horty (1993). Frege on the Psychological Significance of Definitions. Philosophical Studies 72 (2-3):223 - 263.
  16. John F. Horty (1990). A Skeptical Theory of Mixed Inheritance. In J. Dunn & A. Gupta (eds.), Truth or Consequences. Kluwer. 267--281.
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  17. John Horty, Perspectival Act Utilitarianism.
    This paper works within a particular framework for reasoning about actions—sometimes known as the framework of “stit semantics”—originally due to Belnap and Perloff, based ultimately on the theory of indeterminism set out in Prior’s indeterministic tense logic, and developed in full detail by Belnap, Perloff, and Xu [3]. The issues I want to consider arise when certain normative, or decision theoretic, notions are introduced into this framework: here I will focus on the notion of a right action, and so on (...)
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  18. John Horty, The Structure of Values and Norms.
    This book provides a unified account of Hansson’s work on values (or preferences), norms, and their interrelations. Although much of the detailed material contained here appears among the numerous articles published by the author over the past decade or so, the book presents this work as a coherent whole. The overall style is formal: definitions are set out, results are established. Readers who do not enjoy formal work in value theory are likely to find little of interest here. But readers (...)
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  19. John F. Horty, Precedent, Deontic Logic, and Inheritance.
    The purpose of this paper is to e»tahlish some connections between precedent-based reasoning as it is studied in the field of Artificial Intelligence and Law, particularly in the work of Ashley, and two other fields: deontic logic and nonmonotonic logic. First, a deontic logic is described that allows lor sensible reasoning in the presence of conflicting norms. Second, a simplified version of Ashley's account of precedent-based reasoning is reformulated within the framework of this deontic logic. Finally, some ideas from the (...)
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  20. John F. Horty, Synthese.
    The purpose of this paper is to explore a new deontic operator for representing what an agent ought to do; the operator is cast against the background of a modal treatment of action developed by Nuel Belnap and Michael Perlo , which itself relies on Arthur Prior's indeterministic tense logic. The analysis developed here of what an agent ought to do is based on a dominance ordering adapted from the decision theoretic study of choice under uncertainty to the present (...)
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  21. Richmond H. Thomason & John F. Horty, A Clash of Intuitions: The Current State of Nonmonotonic Multiple Inheritance Systems.
    Early attempts at combining multiple inheritance with nonmonotonic reasoning were based on straightforward extensions of tree-structured inheritance systems, and were theoretically unsound. In The Mathcmat~'cs of Inheritance Systcrns, or TMOIS, Touretzky described two problems these systems cannot handle: reasoning in the presence of true but redundant assertions, and coping with ambiguity. TMOIS provided a definition and analysis of a theoretically sound multiple inheritance system, accom-.
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  22. John Horty, Reasons and Precedent.
    This paper describes one way in which a precise reason model of precedent could be developed, based on Grant Lamond’s general idea that a later court is constrained to reach a decision that is consistent an earlier court’s assessment of the balance of reasons. The account provided here has the additional advantage of showing how this reason model can be reconciled with the traditional idea that precedential constraint involves rules, as long as these rules are taken to be defeasible.
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  23. John Horty, Skepticism and Floating Conclusions.
    The purpose of this paper is to question some commonly accepted patterns of reasoning involving nonmonotonic logics that generate multiple extensions. In particular, I argue that the phenomenon of floating conclusions indicates a problem with the view that the skeptical consequences of such theories should be identified with the statements that are supported by each of their various extensions.
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