WHEN I WAS a graduate student, before the term “social networks” came into general use, Paul F. Lazersfeld introduced his students to the idea of personal influence as a major factor in decision-making. Robert K. Merton had his seminar students read Georg Simmel line by line, among other matters explicating the ideas of triads and social circles. These teachings formed my introduction to social networks as problemsolving tools in understanding why people went to psychiatrists and how elites were organized. Hans Zetterberg insisted that social theory could and should be systematic. I am grateful to these mentors for getting me started on what became the study of social networks as key methodological and theoretical insights that could help to unpack social phenomena. I remain as much interested in the impact of social networks on social structure and cultural content as I am in the study of networks themselves. This book reflects that bias.
The Cohen Center for Modern Jewish Studies at Brandeis University, my colleagues there, and especially the director, Leonard Saxe, were extremely supportive while I was writing this book making time and intellectual space for the effort. Deborah Grant, managing editor of the Center, turned the manuscript into readable prose. Katherine Ulrich was a meticulous copy editor. I am grateful to the Brandeis Libraries for their wide subscriptions to electronic journals and data bases, making it easier to download an article than to go to my own library and find the hard copy version. Peter Prescott provided sage advice about publishing.
The social network field is so broad that it is almost impossible for a single individual to encompass it and get everything right and make things understandable to the nonmathematically inclined. To the extent that I managed at all is because a number of people have helped and encouraged me. Foremost is James Moody who reviewed an