1 Order, Coordination, and Collective Action among the Undead. 1 Jean-Baptiste Fleury 2 THEMA- Université de Cergy-Pontoise and Alain Marciano 3 Université Montpellier 1, UMR5474 LAMETA, F-34000 Montpellier, France Introduction 7.30 a.m., Grand Central Station (NYC), peak of the peak hours. Thousands of people are running at various paces in every possible direction, in a seemingly chaotic fashion. At more or less the same time of the day, the same occurs in Charing Cross and Victoria stations (London, UK), and Gare du Nord (Paris, France). Yet no major accident or conflict or problem alters the course of these human beings as they dodge their way through the dense crowd, barely touching each other, without any discussion or formal communication with one another. A certain order underlies the apparent chaos of human interactions, and it exists only because individuals follow general and implicit rules – like politeness. Similarly, in more sophisticated situations such as market transactions, individuals do not usually fight each other, and transactions proceed in an orderly and peaceful way. Accidents occur, but they are exceptional compared to the vast number of transactions that take place. Apparently, living human beings are able to interact and to coordinate themselves with others spontaneously, that is, without resorting to any formal, explicit agreement between them or 1 We thank Glen Whitman and James Dow for the very important and insightful comments they made on preliminaries versions of our paper. 2 Jean-Baptiste Fleury, Université de Cergy-Pontoise, THEMA, UMR CNRS 8184, F-95000, Cergy-Pontoise; jbfleury@gmail.com. 3 Alain Marciano, Université de Montpellier 1, Faculté d’Economie, Avenue Raymond Dugrand, CS 79606, F- 34960 Montpellier cedex 2 France; alain.marciano@univ-montp1.fr.