BY CHRIS EDWARDS
WORLD HISTORY IS NOT a subject; it is all subjects. As soon as the world historian starts asking questions about why peoples in different geographic regions developed differently, she will find herself asking questions about the motivations of individuals, the actions of groups, the patterns of disease, climate, geography, and even the historical effects of continental drift; this pursuit necessitates an understanding of psychology, sociology, biology, geography, climate science, and geology. World historical questions have no respect for disciplinary boundaries, which is why the field attracts polymaths.