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Ought to BeIn John Horty (ed.), Agency and deontic logic, Oxford University Press. 2001.Supplements the background theory of indeterministic time with a standard deontic logic, representing what ought to be the case. Taken together with the formal notion of action introduced in the previous chapter, the framework now allows us to speak about what it ought to be that the agent does, and to explore the possibility that this notion should be identified with the notion of what the agent ought to do. Examples are developed to show that the two notions should not be identified.
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Ought to DoIn John Horty (ed.), Agency and deontic logic, Oxford University Press. 2001.An analogy is developed between action in an indeterministic setting and choice under uncertainty, as it is studied in decision theory. Various dominance relations among actions are explored, and used both to provide a semantic account of what agents ought to do and to formulate a notion of dominance act utilitarianism. The ideas are related to problems involving independence, conditionals, and sure‐thing reasoning.
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Conditional OughtsIn John Horty (ed.), Agency and deontic logic, Oxford University Press. 2001.The notion of what an agent ought to do is refined to yield a notion conditional obligation, representing what the agent ought to do under various circumstances. Patterns of reasoning in the conditional deontic logic are explored. In contrast to the dominance account developed earlier, a competing notion of orthodox act utilitarianism is formulated.
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Strategic OughtsIn John Horty (ed.), Agency and deontic logic, Oxford University Press. 2001.The notion of what an agent ought to do at a moment is generalized to yield a notion of what the agent ought to do over extended periods of time. This requires us to develop the notion of a strategy as a function from moments to actions available at those moments and appropriate notions of strategic dominance. A strategic ought operator is introduced and used to analyze the debate between actualists and possibilists concerning the ways in which an agent's obligations depend on his or her future …Read more
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Indeterminism and AgencyIn John Horty (ed.), Agency and deontic logic, Oxford University Press. 2001.Develops the formal theory of action, or agency, that forms the background of the book. The account is cast against the background of Prior's theory of branching, or indeterministic, time. Against this background, the chapter develops precise notions of action and ability for both individuals and groups.
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Group OughtsIn John Horty (ed.), Agency and deontic logic, Oxford University Press. 2001.The notion of what an agent ought to do is generalized to yield a notion of what groups of agents ought to do. Relations among the obligations governing groups and subgroups are explored, as well as the connections among different species of individual act utilitarianism, group act utilitarianism, and rule utilitarianism.
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The Logic of Precedent: Constraint, Freedom, and Common Law ReasoningCambridge University Press. 2024.Unlike statutory law, which relies on the explicit formulation of rules, common law is thought to emerge from a complex doctrine of precedential constraint, according to which decisions in earlier cases constrain later courts while still allowing these courts the freedom to address new situations in creative ways. Although this doctrine is applied by legal practitioners on a daily basis, it has proved to be considerably more difficult to develop an adequate theoretical account of the doctrine it…Read more
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10Nonmonotonic LogicIn Lou Goble (ed.), The Blackwell Guide to Philosophical Logic, Blackwell. 2017.The goal of a logic is to define a consequence relation between a set of formulas Γ and, in most cases, an individual formula A. This definition generally takes one of two forms. From a proof theoretic standpoint, A is said to be a consequence of Γ whenever there is a deduction of A from the set Γ, viewed as a set of premises; from a model theoretic standpoint, A is said to be a consequence of Γ whenever A holds in every model that satisfies each formula in Γ.
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Handbook of Deontic Logic and Normative System, Volume 2 (edited book)College Publications. forthcoming.
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22Modifying the reason modelArtificial Intelligence and Law 29 (2): 271-285. 2020.In previous work, I showed how the “reason model” of precedential constraint could naturally be generalized from the standard setting in which it was first developed to a richer setting in which dimensional information is represented as well. Surprisingly, it then turned out that, in this new dimensional setting, the reason model of constraint collapsed into the “result model,” which supports only a fortiori reasoning. The purpose of this note is to suggest a modification of the reason model of …Read more
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105Agency and deontic logicOxford University Press. 2001.John Horty effectively develops deontic logic (the logic of ethical concepts like obligation and permission) against the background of a formal theory of agency. He incorporates certain elements of decision theory to set out a new deontic account of what agents ought to do under various conditions over extended periods of time. Offering a conceptual rather than technical emphasis, Horty's framework allows a number of recent issues from moral theory to be set out clearly and discussed from a unif…Read more
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39Reasoning with dimensions and magnitudesArtificial Intelligence and Law 27 (3): 309-345. 2019.This paper shows how two models of precedential constraint can be broadened to include legal information represented through dimensions. I begin by describing a standard representation of legal cases based on boolean factors alone, and then reviewing two models of constraint developed within this standard setting. The first is the “result model”, supporting only a fortiori reasoning. The second is the “reason model”, supporting a richer notion of constraint, since it allows the reasons behind a …Read more
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10Reasons as DefaultsOxford University Press USA. 2012.Although the study of reasons plays an important role in both epistemology and moral philosophy, little attention has been devoted to the question of how, exactly, reasons interact to support the actions or conclusions they do. In this book, John F. Horty attempts to answer this question by providing a precise, concrete account of reasons and their interaction, based on the logic of default reasoning. The book begins with an intuitive, accessible introduction to default logic itself, and then ar…Read more
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Some Aspects of Meaning in Non-Contingent LanguageDissertation, University of Pittsburgh. 1986.Frege's writings on meaning are often interpreted within the framework of possible worlds semantics. The resulting theories rely on contingency to account for a variety of linguistic phenomena, such as the behavior of expressions in propositional attitude contexts, or the idea that a definition might fix the reference of an expression without establishing its meaning. In this thesis, I interpret Frege's ideas within a different framework, to provide a semantic theory that is able to account for …Read more
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82Evaluating new options in the context of existing plansArtificial Intelligence 127 (2): 199-220This paper contributes to the foundations of a theory of rational choice for artificial agents in dynamic environments. Our work is developed within a theoretical framework, originally due to Bratman, that models resource-bounded agents as operating against the background of some current set of intentions, which helps to frame their subsequent reasoning. In contrast to the standard theory of rational choice, where options are evaluated in isolation, we therefore provide an analysis of situations …Read more
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62A sceptical theory of inheritance in nonmonotonic semantic networksArtificial Intelligence 42 (2-3): 311-348. 1990.inheritance reasoning in semantic networks allowing for multiple inheritance with exceptions. The approach leads to a definition of iaheritance that is..
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73Frege on definitions: a case study of semantic contentOxford University Press. 2007.The book begins by focusing on the psychological constraints governing Frege's notion of sense, or meaning, and argues that, given these constraints, even the ...
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176The deliberative stit: A study of action, omission, ability, and obligation (review)Journal of Philosophical Logic 24 (6). 1995.
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94This 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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92A factor-based definition of precedential constraintArtificial Intelligence and Law 20 (2): 181-214. 2012.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. The…Read more
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72An appreciation of John Pollock's work on the computational study of argumentArgument and Computation 3 (1). 2012.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…Read more
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218Reasoning with moral conflictsNoûs 37 (4). 2003.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 A involves buying a lavish gift for a friend, while B involves depositing a c…Read more
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281Reasons as DefaultsPhilosophers' Imprint 7 1-28. 2007.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. F…Read more
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