This chapter addresses the twentieth-century Catholic mystic Thomas Merton. Specifically, it approaches Merton’s mysticism by looking at marginalia found in books he read. Merton’s annotations in these books generally take the form of noting key passages by underlining them or placing marks next to them in the margins of the page. These marked passages thus offer the reader a sense of the elements of mysticism that held interest for Merton. A consideration of Merton’s marginalia has three points of significance for the study of mysticism: first, it addresses the figure of the scholar-practitioner, in that Merton’s study of mystical literature was connected to his own practice of a mystical life; second, it is relevant to the field of comparative mysticism, in that the books Merton annotated come from diverse religious traditions; third, and most fundamentally, it considers mysticism as a hermeneutical practice, in that Merton’s marginalia suggest a mysticism that is related to his reading and interpretation of mystical texts. Even more, this is a mysticism that might move beyond the edge of the page that Merton marked and into the consciousness of later readers.