1 The Emergence of Parties: An Agent-Based Simulation Darren Schreiber University of California, Los Angeles dschreib@ucla.edu Abstract: This paper demonstrates that classic results of Downs, Duverger, Riker, and Sundquist can be seen as emergent consequences of five simple rules for iteratively forming coalitions and adjusting policy platforms. Using simulation, I create a distribution of agents who form coalitions within a political body. By modifying and omitting the basic rules, I compare the results from plurality and majority-seeking actors and from policy-seeking, office-seeking, and mixed-strategy coalitions. ***Animations of this model are available at http://www.bol.ucla.edu/~dschreib.