Despite the fact that the Vienna Convention prescribes a holistic approach to treaty interpretation, it is widely believed that the dominant interpretive approach in international law is textualism. Textualism is premised on the distinction between what is inside and what is outside the text of a treaty and assumes that it is possible to interpret a text without reference to factors that are extraneous to it. This chapter situates the preference for textualism in the intellectual history of the discipline. Building on philosopher John Searle’s work, it argues, however, that no treaty interpreter is or can be a textualist. It also introduces the concept of intertextuality and discusses the tension between the official functions of textualism and the practice of treaty interpretation.