In the aftermath of World War II, many internationalists diagnosed the fundamental cause of international conflict as humanity’s failure to realize the ideals of a world community grounded in global political institutions and common values. To prevent an apocalyptic third world war, internationalists affiliated with the United Nations Educational, Scientific and Cultural Organization (Unesco) identified two ways science could engineer a peaceful and prosperous world community: “technologically, by changing the material conditions of life, work and production; and intellectually, by changing the way in which men think.” Grounded in archival research in four countries, “Patterns of Science” explores both strategies through studies of Unesco’s environmental and social sciences programs. Environmental scientists emphasized the need to balance nature’s books by adapting the pattern of natural resources exploitation to the requirements of global population growth. They conceived of scientifically guided development as a moral equivalent of war that could unite an international army for the conquest of nature. Social scientists stressed the importance of reforming parochial cultural patterns to construct “the defences of peace in the minds of men.” By facilitating intercultural understanding, social scientists would help nations realize the ideal of “unity in diversity.” The goal of both strategies was to produce objective global knowledge that would make the world scale real—“in the minds of men” as well as for politicians and planners. “Patterns of Science” reveals how internationalist scientists attempted to navigate the politics of the cold war, decolonization, and bureaucratic rivalries through case studies that demonstrate the interaction of international, national, and local scales. These cases range from the Los Angeles School District’s implementation of a “Unesco program” during the height of McCarthyism to the establishment of a university chair of race relations in Southern Rhodesia, and from an arid lands research program that pitted “men against the desert” to the production of a Soil Map of the World. Although often mired in controversy or dismissed as naïve, Unesco’s work produced an international community of experts and global social and environmental knowledge that proved crucial to the emerging imperative for sustainable development in the early 1970s.