Contrary-to-duty obligations
type: Item
instance of: scholarly article
title: Contrary-to-duty obligations
zbMATH Open document ID: 0873.03025
DOI: 10.1007/BF00370671
author: Henry Prakken
author: Marek Sergot
published in: Studia Logica
publication date: 1997-10-26T00:00:00Z
review text: The authors argue successfully that a distinction must be drawn between contrary-to-duty reasoning and defeasible deontic reasoning. Consider the following three sentences: i) You must come to the faculty meeting. ii) If you are seriously ill, you do not have to attend the faculty meeting. iii) If you do not come the faculty meeting you must inform the dean that you will be absent. ii) defeats i), in the sense that i) does not apply under the circumstances when ii) applies. This is a case of defeasible reasoning. In contrast, i) can coexist with iii), which applies due to violation of i). The authors argue that defeasible deontic reasoning can be modelled in the same way as defeasible non-deontic reasoning, whereas contrary-to-duty reasoning requires a different type of formalization. For both purposes, they employ a similarity relation between worlds, but it is not used in the same way. In defeasible reasoning, one selects among the worlds in which the antecedent is true those that are close enough, or maximally close, to the actual world. In contrary-to-duty reasoning, they say, one should select, also among the worlds in which the antecedent is true, those that are ideal (``best''). The formal properties of these two selection mechanisms do not seem to coincide. The conceptual distinctions are drawn in this paper with unusual clarity, and the formal results, although unsurprising, are competently developed. This is an important contribution to the discussion on contrary-to-duty obligations.
reviewed by: Sven Ove Hansson
Mathematics Subject Classification ID: 03B45
Mathematics Subject Classification ID: 03A05
Mathematics Subject Classification ID: 03B60
zbMATH DE Number: 929964
zbMATH Keywords: deontic logic
zbMATH Keywords: defeasible reasoning
zbMATH Keywords: contrary-to-duty obligations
MaRDI profile type: Publication
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full work available at URL: https://doi.org/10.1007/bf00370671
OpenAlex ID: W2077212436
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description: scientific article; zbMATH DE number 929964