The scene is a corridor outside a lecture hall. Students are discussing a lecture they have just heard. Among them is a group of three students: a good student (Star), an angry young student (Angry), and a more pragmatic student (Prag).

Star: Oh, what an interesting lecture! The Professor is so knowledgeable, so entertaining! All those clever examples, all those interesting little anecdotes!

Angry: Anecdotes is right. Entertaining, sure. But is there anything beyond anecdotes and entertainment in social software? I may be in a computer science department, but I like to think of myself as a philosopher. In philosophy,...

During the discourse, Angry raised several questions. I thought that Star’s answers were very good, but perhaps a slight feeling of incompleteness remained.

Two questions raised by Angry were, “Why do we need a new term for something old?” and “IsSocial Softwareof any use anyway?”¹

Rather than address these questions directly, perhaps I should say something about how I see social software myself.

But before that, let me cite, with approval, two comments made in the dialogue, one by Star and the other by Angry, who, while angry, had some insights.

Star says, “Perhaps it is a good...

A computer scientist, a logician and a philosopher have found shelter at NIAS, an institute for advanced studies in the humanities and social sciences, situated in a couple of luxurious villas in the most prosperous part of Wassenaar, a Dutch place of residence for the affluent near The Hague. The spacious rooms look out on wooded dunes. NIAS provides a quiet atmosphere for reflection, and it is also renowned for the quality of its lunchtime meals. What follows is a digest of some mealtime conversations....

It is a sunny autumn day, and our protagonists have taken their meals outside, to enjoy the mild rays of the September sun. The NIAS cook Paul Nolte, as always glowing with pride while serving out his delicious food, has prepared a traditional Dutch meal today with sausage, red cabbage and pieces of apple.

Computer Scientist: Hmmm, very tasty. Do you all realize that for the first time NIAS has opened its gates to the likes of us? Logic and computer science used to be outside the compass of NIAS. Moreover, all of our other colleagues are pursuing goals of...

Rohit Parikh, visitor to the project, has delivered a NIAS lecture on social software. On the next day, the project members discuss the contents and the reception of his talk. An ethicist (professor of ethics) has joined the project team, and a visiting political scientist is also present.

Logician: It is such a pity I had to miss Rohit’s lecture. And Rohit himself has dashed off now, to a conference in Paris. On the day before the talk, one of the NIAS fellows asked me with a worried look on his face what the word “algorithm” meant that he had...

Our Philosopher, Political Scientist, Logician and Ethicist meet yet again at a conference after lunch, and are joined by some new discussants: a Computer Programmer and a Cognitive Scientist, and the discussion is moderated by a Chair.

Chair: So we are here today at the Lorentz Center in Leiden to discuss precisely what it is that is the subject of this conferenceGames, Action and Social Software.What is social software? And how is it related to the social sciences?

Logician: We have already discussed the question of demarcating social software from several angles in the first few discourses. For...

An economist is visiting the project. The weather continues to be excellent, permitting the project members and their guest to eat their meals outside on the NIAS terrace again. This time the computer scientist has brought a laptop.

Economist: Your project on Games, Action and Social Software is intriguing, and this is certainly a splendid environment for carrying it out. But I wonder if what you guys intend to develop doesn’t already exist. The field that is calledSocial Choice Theory, isn’t that what Social Software is all about?

Philosopher: Oh, you mean the branch of welfare economics that was...

Our philosopher, economist, political scientist, computer scientist and logician convene yet again after enjoying one of Paul’s lunches. Outside it is showering with heavy rain. Autumn finally seems to have arrived.

Philosopher: It has taken me a while but I think I now see what social software is trying to get at. Its ultimate driving force seems to be a desire to help solve social problems. For this, one should of course understand these problems and get a good grasp of their structure. So, and that’s the second element, we focus on the analysis of such social problems. Finally, the...

Philosopher: Today, I suggest we discuss the important concepts of common knowledge and common belief. As far as I know, the first one to give a formal analysis of these concepts was the philosopher David Lewis, in his bookConvention[140]. One of his examples is traffic conventions, about the role of common knowledge in how one behaves in road traffic. To explain this properly, I wonder if you would care to play a little game with me.

Cognitive Scientist: Sure.

Philosopher: Imagine yourself driving on a one-lane road. You have just come out of the Channel Tunnel on the...

A game theorist has joined the group. Our usual protagonists use the occasion to clarify what game theory and logic might have to say about rationality of actions.

Philosopher: What I would like to understand better is how game theory can help us to understand rational choice, and how this is related to logic. Philosophy has a long-standing interest in rational behavior. The hallmark of rationality is always taken to be the “good reasons for acting” that rational people can give. But game theory seems more concerned with what people actually do than in the reasons they might care to...

The following is a transcript of one of the discussion sessions that took place during the Workshop on Games, Action and Social Software at the Lorentz Center in Leiden. The discussion theme was set by the workshop organizers: “Is logic useful for the analysis of protocols, and if so, how?” The theme has attracted the usual protagonists, plus a cognitive scientist and a specialist in computer security.

Logician: The workshop organizers have asked me to chair this session. I suppose the first thing we should establish is that everyone present here understands the question at hand in the same way....

The next day, the participants in the discussion on protocol analysis reconvene. This time, they have an in-depth exchange of ideas on possible uses of epistemic logic.

Logician: Yesterday we concluded that there are many things that need to be formalized for the analysis of security protocols. After a good night’s sleep, I have the feeling that this may be a nice field of application for some kind ofdynamicepistemic logic. It is about updates of knowledge after the passing of messages, and the protocols are designed to fulfill requirements in terms of knowledge or belief.

Computer Scientist: Yes,...

A concern of the organizers of the workshop on ‘Games, Action and Social Software’ is that although everyone is keen to use logic for the analysis of key concepts in this area, it is not so clear which logic or which tools from logic to use for investigating games, actions and social software. For this reason, they have organized a discussion session on the theme “Battle of the Logics: Temporal Logic, Dynamic Logic, Game Logic, Logic for Belief Revision … Are There too Many?” Participants in the discussion are logicians of four different stripes: a Temporal Logician, a Dynamic Logician,...

Jan and Rineke are having a discussion while making preparations for their farewell talk at NIAS. They have already sent out a title and an abstract.

Rineke: Have you seen the instructions for the NIAS lectures? They frighten me a bit, really. Listen to this: NIAS talks should combine scientific depth with general accessibility; they should be geared at the general NIAS audience, but they should definitely be more than just superficial overviews.

Jan: I suppose we should not only talk about ignorance but we should also presuppose ignorance. Ignorance about logic, that is. Can you show me our abstract...

A sociologist is visiting, on a mission to discuss the problem of collective rational action. The other participants are our familiar protagonists: logician, computer scientist, philosopher. Two other project visitors, an economist and a game theorist, have joined the discussion out of curiosity. The computer scientist has brought his laptop, with wireless Internet connection.

Sociologist: Nice project you’ve got going here guys. A pity your project description fails to mention sociology as a relevant discipline. After all, the problem of collective rationality is a key issue in my field.

Computer Scientist: When the project description talks about “the social sciences”,...

Philosopher: Our project is drawing to an end, and our previous discussion has made clear that it will not be so easy for the social software enterprise to address, let alone cure, the ills of society. To get the discussion going, I would like to start today with a quote that I found in a collection of talks from the physicist Richard Feynman. It is from one of the pieces inThe Pleasure of Finding Things Out,a digest of a talk on “The Value of Science”. The talk starts like this:

From time to time, people suggest to me...