In the last quarter of the 20th century, Robert Cairns helped to transform psychology. In doing so, he rescued it from a virulent susceptibility to reductionism. Standing on the shoulders of great psychologists of the first half of that century (James Baldwin and Kurt Lewin most readily come to mind), he created a truly interdisciplinary environment at Chapel Hill. The Carolina Consortium on Human Development became an international crossroad for the establishment of a new synthesis termed developmental science. A legion of graduate students, postdoctoral Fellows, young faculty, and many senior investigators emerged from this oasis with a deeper, more nuanced understanding of human development. By formulating sound theory and exacting the highest standards for basic research, Cairns and his colleagues moved the field into a realm in which social behavior was not reducible: not to motivations or environmental contingencies any more than to neurons or molecules. Behavior was not sacrificed to biology, nor was it glorified to the environment. Rather, a coherence of behavior and biology was refined in a manner that was intellectually robust and scientifically challenging. Evolution, genetics, ontogeny, and social relationships were interwoven with honesty and with appropriate appreciation for the subtleties involved.

In this volume a group of accomplished protégés and admirers of Cairns explore the nature of aggression, an area of social behavior that most intrigued him. How is it that a social species tolerates aggression?