Table Of ContentDiscourses on Social Software
edited by Jan van Eijck1 and Rineke Verbrugge2
with an introduction by Krister Segerberg
1 CentreforMathematicsandComputerScience(CWI)
Kruislaan413
1098SJAmsterdam,TheNetherlands
2 InstituteofArtificialIntelligence
UniversityofGroningen
GroteKruisstraat2/1
9712TSGroningen,TheNetherlands
[email protected], [email protected]
Table of Contents
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Introductory Conversation
Krister Segerberg . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Replies to Angry, Prag and Star
Rohit Parikh . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
What is Social Software?
Jan van Eijck, Rohit Parikh . . . . . . . . . . . . . . . . . . . . 37
A Guest Lecture on Social Software
Jan van Eijck . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Social Software and the Social Sciences
Keith Dowding, Rineke Verbrugge . . . . . . . . . . . . . . . . 61
On Social Choice Theory
Jan van Eijck . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
Ends and Means, Values and Virtues
Jan van Eijck, Martin van Hees . . . . . . . . . . . . . . . . . . 93
Common Knowledge and Common Belief
Hans van Ditmarsch, Jan van Eijck, Rineke Verbrugge . . . . . 107
Game Theory, Logic, and Rational Choice
Johan van Benthem, Jan van Eijck . . . . . . . . . . . . . . . . 133
What is Protocol Analysis?
Francien Dechesne, Jan van Eijck,
Wouter Teepe, Yanjing Wang . . . . . . . . . . . . . . . . . . . 147
Protocol Analysis and Dynamic Epistemic Logic
Francien Dechesne, Jan van Eijck,
Wouter Teepe, Yanjing Wang . . . . . . . . . . . . . . . . . . . 161
Battle of the Logics
Barteld Kooi, Rineke Verbrugge . . . . . . . . . . . . . . . . . . 177
4 TableofContents
Eating from the Tree of Ignorance
Jan van Eijck, Rineke Verbrugge . . . . . . . . . . . . . . . . . 197
On Collective Rational Action
Jan van Eijck . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217
Social Software and the Ills of Society
Jan van Eijck, Rohit Parikh, Marc Pauly, Rineke Verbrugge . . 237
Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265
Preface
This book has its genesis in a multi-disciplinary project “Games, Action and
Social Software”, which was carried out at the Netherlands Institute for Ad-
vanced Studies in the Humanities and Social Sciences (NIAS) in Wassenaar,
from September 2006 through January 2007. This project brought together
a group of creative researchers from philosophy, logic, computer science, cog-
nitive science and economics, to investigate the logical, computational and
strategic aspects of social mechanisms. The aim was to arrive at a multi-
disciplinary perspective, and help create an active community with a more
definite agenda. One of the deliverables of the project was to be an overview
of this emerging new field, and with an agenda for further research, with the
contents of the book to be shaped by discussions and interaction at NIAS.
Even though we had promised just one book as a collective deliverable of
the project, it soon turned that it would also be worthwhile to publish two
books. The present book is meant as an overview aimed at a wider audience.
A second volume collects a set of chapters presenting the research that the
group of affiliated researchers carried out as part of the NIAS project, indi-
vidually and in small interdisciplinary subgroups. This second book, which
has a more conventional flavour than the present volume, will appear in the
“Studies in Logic” series published under the editorship of Dov Gabbay by
College Publications in London, under the title Games, Actions and Social
Software.
Thecorethemegroupofthe“Games,ActionandSocialSoftware”project
was led by Jan van Eijck, from CWI, Amsterdam and Uil-OTS, Utrecht,
and Rineke Verbrugge, from the Institute for Artificial Intelligence of the
University of Groningen. The other team members were Barbara Dunin-
K¸eplicz, from the Institute of Informatics, of Warsaw University and the Pol-
ish Academy of Sciences, Martin van Hees, from the Philosophy Department
of the University of Groningen, and Krister Segerberg, from the Institute of
Philosophy at the University of Uppsala. In the course of the project several
scholars joined this core group for shorter or longer visits: Johan van Ben-
them from the University of Amsterdam, Marc Pauly from Stanford Univer-
sity, Barteld Kooi from the University of Groningen, Keith Dowding then of
the London School of Economics, now at the Australian National University,
Camberra,RohitParikhfromtheCityUniversityofNewYork(CUNY),Hans
van Ditmarsch from the University of Otago, New Zealand, Peter G¨ardenfors
from Lund University, Andrzej Szalas from Link¨oping University, and Nicola
Dimitri from the University of Siena. They all contributed in one way or an-
6 Preface
other to this volume, even if not all their names show up as chapter authors.
Computer science, philosophy and logic have witnessed a shift of interest
from the study of individual rational action to the study of rational interac-
tion. Examples of the first are computation of an output from a given input
in computer science, individual rationality in philosophy, inference systems
modelling a single idealized reasoner in logic. Examples of rational interac-
tionarecommunicatingsystemsincomputerscience,rationalcommunitiesin
philosophy, interactive proof systems and multi-modal logics modeling inter-
actionofagentsinlogic. Aswehopetoshowinthesediscourses,thestudyof
intelligent interaction is highly relevant for society as a whole. It is certainly
true in the case of social software that a new field is emerging.
When the project actually started in September 2006, we soon discov-
ered that all of us had embarrassing gaps in our understanding of what the
other disciplines in the project had on offer for our common enterprise. So
we decided to make a virtue out of a necessity, by elevating the achievement
of common understanding to the status of one of the project goals, and by
making it our aim to write in-depth overviews of a number of core topics, in
the literary form that was also used by Galileo Galilei in 1632 for his Dia-
logue Concerning the Two Chief World Systems, his famous comparison of
the Copernican world view with that of Ptolemy. Heyting’s introduction to
intuitionistic mathematics [117] comes to mind as a more recent example.
This book was written in the form of a discussion between a classical mathe-
matician, a formalist, an intuitionistic mathematician, a finitistic nominalist,
a pragmatist, and a significist. Other sources of inspiration for this format
were the dialogues on theoretical computer science which often appear in the
EATCS Bulletin [201], the delightful dialogues by Raymond Smullyan (“Is
God a Taoist?”, in The Tao is Silent [215]), and the dialogues in Hofstadter’s
G¨odel, Escher, Bach [119].
Giventhebroadscopeofourproject,theadoptionofthediscourseformat
was a natural way to start our quest for an overview of rational interaction.
Thepresentvolumecanbeviewedasafirststeptowardsamoreunifiedpicture
of the emerging field of social software and of the different factors generating
social complexity. Providing such a picture was among the original project
goals.
More specific issues mentioned in the project description, such as the de-
velopment and refinement of general theories of intelligent interaction, or the
analysis of specific social mechanisms for voting, decision making, exchange
of goods and services, auctioning, and so on, will be dealt with in the other
project book.
Preface 7
The intended readership of the present volume is quite broad: we hope
the book will appeal to a wide range of scientifically minded readers willing
to look beyond the borders of their own specialisms. Anyone to which this
descriptionapplies,andwhohasabitofknowledgeofmathematicsandlogic,
should be able to grasp what goes on in the discourses. We have tried to
make sure that specific expertise in any of the fields contributing to “Games,
Action and Social Software” is not required.
A few words about the intellectual genesis of the chapters are in order.
TwoofthediscoursesinthisvolumearedirectlyconnectedtoNIASseminars
organized by our project. The NIAS Seminar series given by fellows of the
current research group is a sequence of lectures set up each academic year by
the Rector of the Institute. The lectures are meant to appeal to interested
partiesfromawiderangeofbackgrounds,andarehighlightsoftheintellectual
lifeatNIAS.“SocialSoftware”wasaguestseminardeliveredbyprojectvisitor
Rohit Parikh on 19 October 2006. This is the topic of A Guest Lecture on
Social Software starting on page 51. “Eating from the Tree of Ignorance”,
the NIAS seminar on 25 january 2007 that marked the end of the project,
is the topic of the Chapter with the same name starting on page 197. The
feedback from NIAS fellows and staff that these lectures generated has been
invaluable for shaping the discourses. The Chapter On Social Choice Theory
was inspired by an overview of social choice theory presented by Martin van
Hees during the first project month.
TheLorentzworkshopGames, Action and Social Softwarethattookplace
at the Lorentz Centre in Leiden on October 30—November 3, 2006, has also
been important for the creation of this book. In the break between lectures
by international speakers, an hour was scheduled each afternoon after lunch
for structured discussion. Themes for these discussions were Social software:
whatisit?,Protocolanalysis,BattleofthelogicsandTheroleoflogicingame
theory. The results from these discussions were used in the discourses in the
book.
The discourse on Game Theory, Logic and Rational Choice (page 133)
is based on a hand-out from Johan van Benthem for a talk in Beijing in
Summer 2006. The discourse On Collective Rational Action (page 217) has
its genesis in a Maagdenhuis lecture organized by Johan van Benthem and
delivered by Jan van Eijck (February 19, 2007), where Abram de Swaan was
among the audience; the text benefited from many perceptive comments by
DeSwaan. ThediscourseonSocialSoftwareandtheIllsofSociety (page237)
was inspired by an extended email conversation between its four authors in
early 2007.
8 Preface
Marco Swaen created four page-size drawings that illustrate themes from
the book, on pages 49, 132, 159 and 236.
The way the book came into being owes much to the general cultural
atmosphere at NIAS, and we very much hope that some of the pleasure that
we derived from putting the dialogues together shows through in the finished
product.
Jan van Eijck and Rineke Verbrugge
Acknowledgements 9
Acknowledgements
We are grateful to the NIAS staff, in particular to NIAS rector Wim Block-
mans and to NIAS head of research planning and support Jos Hooghuis, for
theiropen-mindednessinwelcomingourratherunusualprojectteamatNIAS,
and for making us feel genuinely at home. Our project operated in a rather
different fashion from the rest of NIAS. While the individual fellows quietly
carriedouttheirlearnedstudies,draftingtheirpapersandwritingtheirbooks
in the splendid isolation of their comfortable NIAS offices, our group’s first
demand was for whiteboards, so that we could scribble formulas and discuss
them in unruly meetings and impromptu workshops. The project gatherings
also drew unusually large groups of PhD students from around the Nether-
lands, often hungry and arriving just in time for lunch. Also, we had new
project visitors almost every week. Still, the NIAS staff never complained,
andallpracticalmatterswerehandledverysmoothly,withgeneroushelpfrom
RitaBuis,RinkvandenBosch,AnnetteBottema,RuudNolteandSaskiavan
der Holst-Pels.
We gratefully acknowledge NWO, the Netherlands Organization for Sci-
entific Research, for enabling the thematic NIAS group ‘Games, Action and
Social Software’ both by Advanced Studies grants 051-04-120 for the project
group and by Replacement grant 400-05-710 covering a lecturer at the Uni-
versityofGroningenduringRinekeVerbrugge’sstayatNIAS.Thanksalsoto
the Centre for Mathematics and Computer Science (CWI) for allowing Jan
van Eijck to take part in the NIAS project.
We thank the Lorentz Center in Leiden for a generous grant, support-
ing the workshop at which four of the discussions leading to this book took
place. The relaxed atmosphere and the unique facilities at the Lorentz Cen-
tre fostered lively discussions during the workshop on Games, Action and
Social Software, which sometimes went on into the late evening. We would
like to thank Martje Kruk, Wim van Saarloos, Gerda Filippo and Henriette
Jensenius for their wonderful enthusiasm and highly professional support.
Several people helped and stimulated us with their feedback on the dis-
courses. FloorSietsmamadeusunderstandthataprefacecouldnotbemissed
from a book like this. Rob Economopoulos wrote a long commentary on the
discourse on collective rational action. Kathy van Vliet-Leigh helped with
editing the first dialogue (which also appeared in a NIAS newsletter [81]).
Heleen Verleur’s reaction to her husband’s growing concern and agitation
while he was reading up on climate change led to the discourse on social
softwareandtheillsofsociety. AbramdeSwaansentushisdetailedandper-
10 Acknowledgements
ceptive comments on the discourse on collective rational action. Alan Taylor
and Don Saari answered questions about issues in the discourse on social
choice theory. Davide Grossi assisted with the proofreading, and Krzysztof
Apt made a helpful suggestion for the first discourse. Donald Light, NIAS
fellow during the academic year 2006-2007, participated in many discussions
about collective rationality and ethics. Paul van den Broek, Lorentz fellow
2006-2007,discussedissuesincognitivesciencewithus. NIASfellowsDickvan
Lente and Peter Kroes stimulated us with their interest in what our project
was up to. With Mohammad Bagheri, Lorentz fellow, we talked about puz-
zles of knowledge and social interaction; Mohammad also introduced us to
wonderful Persian music. All other fellows stimulated us with their attitudes
ranging from genuine interest, pleasant skepticism, eagerness to understand,
and willingness to consider connections with broader issues.
The editors of the new series Texts in Logic and Games which started to
appear with Amsterdam University Press end of 2007, Johan van Benthem,
Wiebe van der Hoek, Bernhard von Stengel, Robert van Rooij and Benedikt
L¨owe, were almost immediately enthusiastic about our plans, and they were
invariablyencouragingandhelpful. BenediktL¨owehasmanagedtofindcom-
petent and thorough reviewers for the individual chapters. The report that
thisgeneratedwereofgreathelptous,andwethankallrefereesfortheirmuch
appreciated efforts. We are proud that this volume is appearing as a Text in
Logic and Games. Joel Uckelman helped us with the LATEX formatting.
OurfinalthanksgotoPaulNolteforcookingthedeliciousNIASlunchtime
meals that are referred to in the text.
