Much has been written on the causes of war; little has been learned about the subject. There are two reasons for this. The first is that the theoretical assumptions used to study the phenomenon are flawed and often erroneous. The second is that individual scholars have tried to do too much too soon. Typically, a single scholar working alone has tried to review a number of wars, reflect on their commonalities, and reach a conclusion. The end result has been some insightful suggestions, but little real evidence or documented generalizations. In the last twenty-five years, this has begun to change. Building on the pioneering efforts of Lewis Richardson and Quincy Wright, a community of peace researchers has emerged, with scholars testing very specific hypotheses and trying to document in a rigorous fashion the patterns of behavior associated with war.

What distinguishes this book on war from previous ones is that it will employ the large number of empirical findings generated in the last twenty-five years as the basis of its theorizing. Although this research has added important pieces of evidence that have moved the field beyond the imprecise and often contradictory explanations of the past, no clear theoretical explanation seems to be emerging from this process, although there is research that suggests such explanations. Because of inconsistencies and anomalies in the findings as well as differences in measurement and research design, the meaning and significance of these findings are hardly self-evident. Rather, they exist as a set of clues or pieces of a puzzle that need to be put together.

A scientific explanation will not just emerge from the research process, but must be constructed carefully from the evidence.