Calls for interdisciplinarity in the humanities often presume the existence of disciplines as separate academic fields, with research collaboration framed as a crossing of the borders between separate areas of knowledge. By way of two case studies and a comparative approach called borderology, the chapter questions such a notion and investigates other aspects of interdisciplinary work as practiced by researchers in the humanities and the social sciences. First, the rich work on modern love by sociologist Eva Illouz, illustrating a form of intrinsic interdisciplinarity, is analyzed. Second, recent work within friendship studies is compared, and borderology is used to shed light upon friendship both as a real phenomenon and as a cluster of concepts invoked and investigated by different disciplines. These examples may help policy makers appreciate one of the ways in which the humanities are always already interdisciplinary.