The is-ought problem. An investigation in philosophical logic
type: Item
instance of: scholarly article
title: The is-ought problem. An investigation in philosophical logic
zbMATH Open document ID: 0927.03005
author: Gerhard Schurz
published in: Trends in Logic -- Studia Logica Library
publication date: 1999-08-09T00:00:00Z
review text: This book is philosophical logic at its best. It applies the rigorous methods and results of formal alethic and deontic modal logic to the long-standing philosophical question of whether Ought is ever derivable from Is, i.e., whether normative statements are ever validly inferable from purely descriptive statements. By addressing this question at a high level of abstraction, the author is able to establish very general results. Chapter 1 sets up the philosophical background of the Is-Ought problem. Chapter 2 develops the formal languages that will be applied to analyzing this problem. These are first-order bi-modal, alethic-deontic languages with or without identity and interpreted in models with or without constant domains and with or without rigid designation. (Hence, there is a variety of languages with respect to which the problem must be addressed.) The alethic modal logic may vary in familiar ways; the deontic logic is based on standard assumptions, where statements \(OA\) are interpreted as true at a point just when \(A\) is true at all \textit{ideal} points. Chapter 3 articulates the Is-Ought problem precisely. There are four distinct `Special Hume Theses' (SH) that no purely normative statement \(N\), not logically true logically follows from a consistent, purely descriptive set of premisses, \({\mathbf D}\), depending on how `purely normative' is construed. There is a more interesting `General Hume Thesis' (GH) that no \textit{mixed} conclusion, \(A\), containing both descriptive and normative components, logically follows from a purely descriptive set of premisses, \({\mathbf D}\), unless \(A\) is `Ought-Irrelevant' to \({\mathbf D}\), i.e., unless the result of substituting any predicate for the predicates within the scope of the `ought'-operators of \(A\) would also follow from \({\mathbf D}\). Chapter 4 establishes precise conditions under which (GH) holds. Chapter 5 establishes conditions for (SH), connecting Hume's thesis with Halldén completeness. C…
Mathematics Subject Classification ID: 03A05
Mathematics Subject Classification ID: 03-02
Mathematics Subject Classification ID: 03B45
zbMATH DE Number: 1322227
zbMATH Keywords: alethic logic
zbMATH Keywords: Hume thesis
zbMATH Keywords: philosophical logic
zbMATH Keywords: modal logic
zbMATH Keywords: Is-Ought problem
zbMATH Keywords: deontic logic
zbMATH Keywords: Halldén completeness
zbMATH Keywords: ethical theory
zbMATH Keywords: normative statements
zbMATH Keywords: ineliminable bridge principles
reviewed by: Louis F. Goble
MaRDI profile type: Publication
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description: scientific article; zbMATH DE number 1322227