Systemic integration has made its way into the parlance and practice of international scholars and adjudicators, particularly as a tool against the fragmentation of international law. The chapter analyses it as a particular instance of what Foucault termed ‘problematization’, that is, ‘how and why certain things (behavior, phenomena, processes) became a problem’. In fact, while the issue of fragmentation is not a recent phenomenon, only in the late 1990s did it receive special attention. Why was it so? The question of what drove most international lawyers to present fragmentation as one of the most pressing issues of the time, and the International Law Commission to issue a report on fragmentation and international law, prepared by Martti Koskenniemi in 2006, is examined. The chapter argues that the wide acceptance of the systemic integration principle could be explained by international lawyers’ continuous quest for unity, uniformity, and coherence.