INSTITUTIONAL THEORY 1 Edwin Amenta Kelly M. Ramsey University of California, Irvine Although most political sociologists and political scientists nowadays either consider WKHPVHOYHV RU DUH GHHPHG ｳLQVWLWXWLRQDOLVWVｴ NH\ GLIIHUHQFHV UHPDLQ DPRQJ PDMRU schools of institutionalism (see reviews in Pierson 2000b; Pierson and Skocpol 2002; Amenta 2005). In this chapter we review sociological institutionalism, historical institutionalism, and political institutionalism. 2 We discuss their similarities and differences, theoretical and methodological insights, research gains, analytical problems, and prospects for the study of politics. To focus our discussion, we consider mainly research regarding the development of public policy, the terrain on which many advances in political sociology and political science have taken place and an occasional battleground for these approaches. The basic similarity in all institutional theoretical claims is that something identified at a higher level is used to explain processes and outcomes at a lower level of analysis (Clemens and Cook 1999; Amenta 2005). Institutionalists tend to avoid both individual-level explanations and explanations situated at the same level of analysis. For these reasons, they are sometimes critici]HG DV ｳVWUXFWXUDOO\ ELDVHGｴ WKRXJK WKLV is a feature of institutional arguments that has distinctive explanatory advantages as well as disadvantages. Institutionalists typically have problems in explaining social and