Reasons as Defaults

by Horty, John F.

• ISBN13: 9780199744077
• ISBN10: 0199744076
• Format: Hardcover
• Copyright: 2012-04-25
• Publisher: Oxford University Press

Summary

There has recently been a good deal of discussion of reasons in the philosophical literature, much of it motivated by the idea that the concept of a reason is basic to the normative realm, a fundamental concept in terms of which other normative notions can be analyzed. In this volume, John Horty brings to bear his work in logic to present a framework that allows for answers to key questions about reasons and reasoning, namely: What are reasons, and how do they support actions or conclusions? Given a collection of individual reasons, possibly suggesting conflicting actions or conclusions, how can we determine which course of action, or which conclusion, is supported by the collection as a whole? What is the mechanism of support? This book joins an important and active literature, but it also occupies a unique position. Most of the current work on reasons is concerned with a number of complex philosophical issues, such as, for example, the relation between reasons and motivation, desires, and values, the issue of internalism versus externalism in the theory of reasons, and the issue of objectivity versus subjectivity of reasons. Horty's book, by contrast, concentrates on developing a concrete theory of the way in which reasons might interact to support their outcomes. He brings to the study of reasons and their outcomes the same standards of rigor that Frege first applied in studying the relation between ordinary logical premises and their conclusions.

Author Biography

John Horty is Professor of Philosophy, University of Maryland. He is the author of Agency and Deontic Logic and Frege on Definitions.

Table of Contents

Introduction	p. 1
Default logic	p. 13
A primer on default logic	p. 15
Basic concepts	p. 15
Default rules	p. 15
Priority relations	p. 18
Theories and scenarios	p. 22
Central definitions	p. 25
Binding defaults	p. 25
Proper scenarios and extensions	p. 30
Extensions and conclusions	p. 34
Theories with multiple extensions	p. 34
Theories without extensions	p. 38
From defaults to reasons	p. 41
An austere theory of reasons	p. 41
Developing the theory	p. 47
Conflict, strength, and defeat	p. 47
Reasons and enablers	p. 53
Reason amalgamation	p. 59
Deontic logic	p. 63
Reasons and oughts	p. 65
The two logics	p. 68
Simple oughts	p. 69
Conditional oughts	p. 74
Some history	p. 76
Properties of the logics	p. 80
Moral conflicts	p. 86
Logical objections	p. 87
Agglomeration	p. 87
Other logical objections	p. 92
Conceptual objections	p. 96
Objections based on reasons as moral forces	p. 102
Some elaborations	p. 109
Variable priorities and exclusion	p. 111
Variable priority default theories	p. 111
The definition	p. 111
Some examples	p. 114
Exclusionary default theories	p. 121
The definition	p. 121
Some examples	p. 126
Discussion	p. 130
Downward closure of exclusion	p. 130
Exclusion by weaker defaults	p. 135
Excluders, intensifiers, and attenuators	p. 141
Particularism	p. 147
Dancy's argument	p. 148
Evaluating the argument	p. 150
Discussion	p. 155
Pragmatic considerations	p. 156
Borrowing a book	p. 157
Moderate particularism	p. 160
Some complications	p. 167
Skepticism and floating conclusions	p. 169
Floating conclusions	p. 169
Arguments and paths	p. 170
Two versions of skepticism	p. 174
The problem with floating conclusions	p. 179
An example	p. 179
Objections to the example	p. 183
Discussion	p. 186
Other examples	p. 186
Skepticism	p. 190
Problems with priorities	p. 192
Refining the concept of defeat	p. 192
Controlling the order of application	p. 197
Discussion	p. 206
Inappropriate equilibria	p. 206
Other orderings	p. 209
Reinstatement	p. 211
Appendices	p. 219
Notes on the default logics	p. 221
Proper scenarios	p. 221
Some observations on defeat	p. 227
Normal default theories	p. 228
Notes on the deontic logics	p. 234
A comparison with van Fraassen's logic	p. 234
A comparison with standard deontic logic	p. 238
Bibliography	p. 241
Index	p. 251
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