The author argues for the virtues of diversity in cities, organizations, strategies for development, and human discourse in general. The opening chapter develops the vision of Jane Jacobs (the "diva of diversity") for the development of city regions. Many of the later chapters are based on the author's ten years in the World Bank and Senior Advisor and speechwriter for Joseph Stiglitz. Many of the problems in the World Bank's policies were based on a narrow ideological vision that did not tolerate a diversity of pragmatic approaches to the complex questions of economic and social development. Finally, the narrow social-engineering criterion for evaluating social projects is cost-benefit analysis, and the penultimate chapter develops a logical fallacy in the Kaldor-Hicks Principle that is the theoretical basis for cost-benefit analysis.