Table Of ContentElements of Argumentation
Elements of Argumentation
Philippe Besnardand AnthonyHunter
TheMITPress
Cambridge,Massachusetts
London,England
62008MassachusettsInstituteofTechnology
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LibraryofCongressCataloging-in-PublicationData
Besnard,Philippe,1958–
Elementsofargumentation/PhilippeBesnardandAnthonyHunter.
p. cm.
Includesbibliographicalreferencesandindex.
ISBN978-0-262-02643-7(hardcover:alk.paper) 1.Artificialintelligence. 2.Reasoning.
3.Logic. 4.Informationtechnology. I.Hunter,Anthony,1962– II.Title.
Q335.B489 2008
006.3—dc22 2007032257
10 9 8 7 6 5 4 3 2 1
Preface
Logic-based formalizations of argumentation that take pros and cons for
some conclusion into account have been extensively studied over a num-
berofyears,andsomebasicprincipleshavenowbeenclearlyestablished.
These formalizations assume a set of formulae and then lay out argu-
ments and counterarguments that can be obtained from these assumed
formulae.
More recently, attempts have been made to refine these formalizations
in order to more closely capture practical argumentation as used in the
real world. This has led to techniques for selecting and reforming the
more appropriate arguments and counterarguments for use in problem
analysis and decision making. These techniques identify the better argu-
ments based on (1) taking into account intrinsic aspects of the arguments
such as their relative consistency, the exhaustiveness of the consideration
of counterarguments, and therelativesimilarities between arguments and
(2) taking into account extrinsic factors such as the impact on the audi-
ence and the beliefsof theaudience.
Theaimofthisbookistointroducethebackgroundandtechniquesfor
formalizing argumentation in artificial intelligence and, in particular, to
cover the emerging formalizations for practical argumentation. This cov-
erageincludesconsideringhowargumentscanbeconstructed,howcoun-
terargumentscanbeidentified,howkeyintrinsicandextrinsicfactorscan
be analyzed, and how these analyses can be harnessed for formalizing
practical argumentation. As a part of this coverage, we aim to elucidate
and formalizesome of the key elements of argumentation.
This book focuses on argumentation by an agent presenting a case for
some claim. This involves providing an initiating argument for the claim;
then providing undercuts to this argument; and then, by recursion, pro-
viding undercuts to undercuts. Each undercut is a counterargument that
Contents
Preface ix
Acknowledgments xi
1 NatureofArgumentation 1
1.1 BasicConceptsforArgumentation 2
1.2 InformationInvolvedinArgumentation 6
1.3 AgentsInvolvedinArgumentation 9
1.4 RequirementsforFormalizingArgumentation 13
1.5 FrameworksforFormalizingArgumentation 16
1.6 Discussion 19
1.7 BibliographicNotes 19
2 AbstractArgumentation 21
2.1 Introduction 21
2.2 Acceptability 24
2.3 Cycles 27
2.4 Fixpoints 30
2.5 Discussion 33
2.6 BibliographicNotes 36
3 LogicalArgumentation 37
3.1 Preliminaries 38
3.2 Arguments 39
3.3 Defeaters,Rebuttals,andUndercuts 45
3.4 CanonicalUndercuts 51
3.5 ArgumentTrees 55
3.6 Duplicates 64
3.7 ArgumentStructures 66
3.8 First-OrderArgumentation 68
3.9 Discussion 72
3.10 BibliographicNotes 74
vi Contents
4 PracticalArgumentation 77
4.1 ArgumentationforThinkingaboutQuestions 77
4.2 ArgumentationThatRaisesFurtherQuestions 80
4.3 PolemicalArgumentation 83
4.4 SpeculationalArgumentation 87
4.5 CoalitionsofArgumentsWorkinginHarmony 91
4.6 MakingtheSamePointinDifferentWays 94
4.7 AnalysisofIntrinsicandExtrinsicFactors 97
4.8 SelectiveandFormativeArgumentation 99
4.9 ReflectingNaturalLanguageinLogic 100
4.10 Discussion 104
4.11 BibliographicNotes 105
5 ComparingandRationalizingArguments 107
5.1 JudgingArgumentTrees 108
5.2 DegreeofUndercut 109
5.3 PruningofArgumentTrees 119
5.4 CompressingArgumentTrees 122
5.5 CondensingArgumentTrees 124
5.6 ShiftingCommitmentfromDefenderstoAttackers 127
5.7 Discussion 129
5.8 BibliographicNotes 130
6 ConsideringtheAudience 131
6.1 HigherImpactArgumentation 132
6.2 MoreConvincingArgumentation 144
6.3 CostofUnderstandingArguments 152
6.4 Discussion 154
6.5 BibliographicNotes 156
7 AlgorithmsforArgumentation 157
7.1 BasicAlgorithms 158
7.2 ArgumentCompilation 160
7.3 ArgumentContouring 174
7.4 ApproximateArguments 181
7.5 Discussion 188
7.6 BibliographicNotes 188
8 ComparisonwithRelatedApproaches 191
8.1 ArgumentationBasedonClassicalLogic 192
8.2 ArgumentationBasedonDefeasibleLogic 205
8.3 ArgumentationBasedonInferenceRules 221
8.4 ArgumentationBasedonDefaultLogic 227
8.5 ArgumentativeAttitudes 229
8.6 ArgumentationTechnology 230
8.7 Discussion 233
Contents vii
9 FutureDirections 237
9.1 AssessmentofOurApproach 237
9.2 KeyIssuesforFutureDevelopment 238
9.3 TowardDialogicalArgumentation 248
Appendixes 249
A TableofUniformNotation 249
B ReviewofTrees 251
C ReviewofClassicalLogic 253
C.1 LanguageofClassicalPropositionalLogic 253
C.2 SemanticsforClassicalPropositionalLogic 255
C.3 ConsequenceRelation 259
C.4 ClassicalPredicateLogic 260
D ProofsforResultsinBook 263
Bibliography 285
Index 295
Description:Logic-based formalizations of argumentation, which assume a set of formulae and then lay out arguments and counterarguments that can be obtained from these formulae, have been refined in recent years in an attempt to capture more closely real-world practical argumentation. In Elements of Argumentati
