state of affairs. This appendix reviews briefly some of those assumptions and that methodological literature as they relate to the current investigation of extreme violence in American schools.
Following that examination, the appendix then connects the aims and strengths of case study methodology to the study of extreme, and therefore puzzling, human behavior. The same extremity of deviance that makes such cases rare demands a multilevel conceptualization of the problem to be investigated. The emphasis on discovery of relevant factors through naturalistic methods of inquiry, which is the hallmark of case studies, leads directly to the conceptualization of human behavior as taking place in a set of hierarchically nested systems that underlies several well-established schools of thought and research methodology in psychology and psychiatry. It is precisely when things occur that seem extreme, unprecedented, and difficult to explain that one needs to cast the widest possible net to identify potentially important factors and processes. Viewing human behavior as occurring in a set of hierarchically nested systems is of great heuristic value in this situation, certainly as a way of casting a wide net and potentially as a way of actually catching something in an uncharted sea.
Case studies have a variety of practical uses, including widespread application as teaching texts in such fields as law and business. In recent years, however, the particular and appropriate uses of cases studies as tools for scientific research have been delineated. Yin (1989) has noted that case studies, far from being suitable merely as illustrative material for quantitative analyses using larger samples, can be employed for three distinct and legitimate types of scientific ends: descriptive, exploratory, and explanatory. As an example of how even a single case study can serve explanatory ends, he cites Allison’s study of the Cuban missile crisis, in which the author tests three rival hypotheses against the data (Allison, 1971).
In introducing Yin’s exposition of case methods, Donald Campbell, among the most distinguished of all social science methodologists, contrasts this kind of operation with the highly touted ability of randomized experiments to exclude all rival hypotheses, without, he notes with a large dose of irony, “specifying what any of them are” (Campbell, 1989:8). Campbell invokes the effort to exclude rival hypotheses as the “core of scientific method” (p. 7). In the case of extreme school violence, for example, there may be popular theories, such as “the perpetrators are all the victims of bullying” that might be excluded on the basis of even a single