ABSTRACT Many historians have traced the accumulation of scientific archives via communication networks. Engines for communication in early modernity have included trade, the extrapolitical Republic of Letters, religious enthusiasm, and the centralization of large emerging information states. The communication between Samuel Hartlib, John Dury, Duke Friedrich III of Gottorf-Holstein, and his key agent in England, Frederick Clodius, points to a less obvious but no less important impetus—the international negotiations of smaller states. Smaller states shaped communication networks in an international (albeit (...) politically and religiously slanted) direction. Their networks of negotiation contributed to the internationalization of emerging science through a political and religious concept of shared interest. While interest has been central to social studies of science, interest itself has not often been historicized within the history of science. This case study demonstrates the co-production of science and society by tracing how period concepts of interest made science international. (shrink)