If anyone deserves the title "father of social cognition," it is William J. McGuire who, along with his wife and colleague Claire V. McGuire, has written the target article for this volume. The culmination of many years of work, the article discusses their highly developed theory of human thought systems, and establishes many new directions for theoretical and empirical inquiry. Equally important, however, are the chapters — written from many different theoretical and empirical perspectives — that challenge various assumptions underlying the McGuires' work. In addition to examining implications not explicitly considered in the target article, these contributions explore the new directions that future research and theorizing might take.