Deontic Logic Viewed as Defeasible Reasoning

Conditional deontic logic augmented with defeasible reasoning

Data & Knowledge Engineering ◽

10.1016/0169-023x(95)00008-g ◽

1995 ◽

Vol 16 (1) ◽

pp. 73-91 ◽

Cited By ~ 13

Author(s):

Young U. Ryu

Keyword(s):

Deontic Logic ◽

Defeasible Reasoning

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Defeasibility applied to Forrester’s paradox

South African Computer Journal ◽

10.18489/sacj.v32i2.848 ◽

2020 ◽

Vol 32 (2) ◽

Author(s):

Julian Chingoma ◽

Thomas Meyer

Keyword(s):

Deontic Logic ◽

Defeasible Reasoning ◽

Logic Systems ◽

Legal Domain ◽

Deontic Paradoxes ◽

Logic System

Deontic logic is a logic often used to formalise scenarios in the legal domain. Within the legal domain there are many exceptions and conflicting obligations. This motivates the enrichment of deontic logic with not only the notion of defeasibility, which allows for reasoning about exceptions, but a stronger notion of typicality that is based on defeasibility. KLM-style defeasible reasoning is a logic system that employs defeasibility while Propositional Typicality Logic (PTL) is a logic that does the same for the notion of typicality. Deontic paradoxes are often used to examine logic systems as the paradoxes provide undesirable results even if the scenarios seem intuitive. Forrester’s paradox is one of the most famous of these paradoxes. This paper shows that KLM-style defeasible reasoning and PTL can be used to represent and reason with Forrester’s paradox in such a way as to block undesirable conclusions without completely sacrificing desirable deontic properties.

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Defeasible Tolerance and the Sorites

The Journal of Philosophy ◽

10.5840/jphil2020117413 ◽

2020 ◽

Vol 117 (4) ◽

pp. 181-218

Author(s):

Ivan Hu ◽

Keyword(s):

Deontic Logic ◽

Defeasible Reasoning ◽

Sorites Paradox

I propose a novel solution to the Sorites Paradox. The account vindicates the tolerance of vague predicates in a way that properly addresses the normativity of vagueness while avoiding sorites contradiction, by treating sorites reasoning as a type of defeasible reasoning. I show how this can be done within the setting of a nonmonotonic deontic logic. Central to the proposal is its deontic interpretation of tolerance. I draw a key distinction between two types of tolerance, based on different deontic notions, and show how the account captures key differences between these types of sorites reasoning. I compare the resulting theory to various existing contextualist proposals and argue that it better accounts for the normative aspects of sorites reasoning.

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Dyadic Obligations over Complex Actions as Deontic Constraints in the Situation Calculus

Proceedings of the Seventeenth International Conference on Principles of Knowledge Representation and Reasoning ◽

10.24963/kr.2020/26 ◽

2020 ◽

Author(s):

Jens Claßen ◽

James Delgrande

Keyword(s):

Artificial Intelligence ◽

Deontic Logic ◽

Action Theory ◽

Prima Facie ◽

Situation Calculus ◽

Artificial Agents ◽

Planning Techniques ◽

Course Of Action ◽

Reasoning About Action ◽

The Given

With the advent of artificial agents in everyday life, it is important that these agents are guided by social norms and moral guidelines. Notions of obligation, permission, and the like have traditionally been studied in the field of Deontic Logic, where deontic assertions generally refer to what an agent should or should not do; that is they refer to actions. In Artificial Intelligence, the Situation Calculus is (arguably) the best known and most studied formalism for reasoning about action and change. In this paper, we integrate these two areas by incorporating deontic notions into Situation Calculus theories. We do this by considering deontic assertions as constraints, expressed as a set of conditionals, which apply to complex actions expressed as GOLOG programs. These constraints induce a ranking of "ideality" over possible future situations. This ranking in turn is used to guide an agent in its planning deliberation, towards a course of action that adheres best to the deontic constraints. We present a formalization that includes a wide class of (dyadic) deontic assertions, lets us distinguish prima facie from all-things-considered obligations, and particularly addresses contrary-to-duty scenarios. We furthermore present results on compiling the deontic constraints directly into the Situation Calculus action theory, so as to obtain an agent that respects the given norms, but works solely based on the standard reasoning and planning techniques.

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