wouldn't want full cooperation anyway. As for the first concern, there is no end of modelsthat produce emergent cooperation.22Cooperation can emerge even with the simplest agent rules. Axelrod found that a simple rule of reciprocity was sufficient to generate and sustain cooperation in a community of interacting agents.23Nowak and May have shown that, over time, evolutionary pressures on spatially arranged agents lead to cooperation even in the Prisoner's Dilemma game, a game in which noncooperative behavior is optimal in the one shot setting.24But before we just sit back and wait for the cooperation to come about, we must keep in mind that complex systems also organize themselves intoless desirable states. Most notably, a substantial body of research suggests that many systems have organized themselves into critical states. A critical state is one in which small disturbances can lead to large events, such as earthquakes or stock market crashes.25In systems that self-organize to a critical state, tensions build until the entire system is poised on the verge of collapse. The danger of self-organized criticality warns us against just letting complex systems run.[ED. REQUEST: PLEASE CONFIRM THAT CHANGE ABOVE, FROM “CRITICALITY GUARDS AGAINST” TO “CRITICALITY WARNS US AGAINST,” DOES NOT CHANGE MEANING.] Recent events in financial markets support this claim.Suppose, for a moment, that we accept the complexity of the world. We then mustask, what is to be done? If decentralization and bottom-up processes are so great, does this mean we should just leave all systems to work themselves out? On the one hand, Wood argues for leaving the Leviathan out of this. On the other, we think Wood would 22Robert Axelrod, “On Six Advances in Cooperation Theory,” Analyse & Kritik22 (2000): 130-151.23Robert Axelrod, The Evolution of Cooperation(New York: Basic Books, 1984).24Martin A. Nowak and Robert M. May, “The Spatial Dilemmas of Evolution,” International Journal of Bifurcation and Chaos3:1 (1993): 35-78.25See Per Bak, How Nature Works: The Science of Self-Organized Criticality(New York: Copernicus, 1996).