This is a comprehensive work on one of the key figures in early Chinese-Western relations. Xu Guangqi was one of the first promoters of Western science in China, worked together with the Jesuit Matteo Ricci on translations of Western science, was one of the first Chinese converts, a high-ranking statesman, organizer of a major calendar reform, and introduced Western weapons into the Chinese army. His astonishingly multifarious activities are pieced together within their (Chinese and Western) social, intellectual and cultural context. The result is a composite profile of this complex figure that is anchored in Chinese (and Western) primary sources.