Book excerpt: If he were an assistant professor today, what work would social science giant Donald T. Campbell be doing in the field of organization science? Joel A. C. Baum and Bill McKelvey explore this question in Variations in Organization Science. This volume reveals and celebrates Campbell's many contributions to the field by presenting new variations that stem directly from his work. Rather than analyzing Campbell's work, chapter authors pursue additional implications and further applications of his perspective to organization science - some of which Campbell himself might have pursued if he were starting out as an assistant professor in 1999.