Detachment and defeasibility in deontic logic
type: Item
instance of: scholarly article
title: Detachment and defeasibility in deontic logic
zbMATH Open document ID: 0860.03019
DOI: 10.1007/BF00370667
author: Carlos E. Alchourrón
published in: Studia Logica
publication date: 1997-04-21T00:00:00Z
review text: This paper presents a deontic logic designed to formalize concepts of both defeasible and indefeasible duties, where each may be either categorical or conditional. Defeasible conditional duties are distinguished from their indefeasible counterparts in that principles for strengthening the antecedent and of deontic modus ponens should both fail for the former and both be valid for the latter. Standard conditional deontic logic validates the first principle but not the second; hence it is inadequate for either sort of statement of conditional duties. This paper builds deontic logic upon a logic of defeasible conditionals, \(A>B\), by adding the standard deontic operator \(O\), according to which statements \(OA\) assert that \(A\) holds in all ideal worlds. This represents indefeasible categorical, or actual, duties. Statements of indefeasible conditional duties, \(O(A|B)\) are defined as \(B\Rightarrow OA\), where `\(\Rightarrow\)' represents alethic strict implication. By contrast, statements of defeasible conditional duties, \(Od(A|B)\), are defined in terms of the defeasible conditional, \(B>OB\), and statements of defeasible categorical duties, prima facie duties, \(Od(A)\), are defined as \(Od(A|T)\), i.e., \(T>OA\), where \(T\) is any tautology. These concepts are all defined precisely by means of a possible-worlds semantics, and shown to have desirable properties.
Mathematics Subject Classification ID: 03B60
Mathematics Subject Classification ID: 03A05
zbMATH DE Number: 929960
zbMATH Keywords: deontic logic
zbMATH Keywords: conditional duties
zbMATH Keywords: logic of defeasible conditionals
zbMATH Keywords: categorical duties
zbMATH Keywords: possible-worlds semantics
reviewed by: Louis F. Goble
MaRDI profile type: Publication
cites work: An Analysis of some Deontic Logics
cites work: Q5635426
cites work: The logic of conditional obligation. Comments by Harry Beatty
cites work: Modal logic with subjunctive conditionals and dispositional predicates
full work available at URL: https://doi.org/10.1007/bf00370667
OpenAlex ID: W151947385
description: scientific article; zbMATH DE number 929960