The Introduction presents the book’s general argument. It describes the main objectives and central themes related to the conceptualization of not-knowing. It argues for an anthropology of that which remains nameless in anthropology, lost in the gaps between culture, structure, and process. Not-knowing refers to the difficulty of accounting for certain intense individual and collective experiences that often arise in ritual, spiritual, and religious contexts and, in many ways, defy any attempt at complete rationalization. It deals with situations in which meaning is broken, forcing anthropologists to think beyond reason. It describes how an otherness of a radical nature unfolds before the anthropologist’s gaze, both in its experiential dimension and ethnographic and argumentative construction, as well as the discipline´s blind spots. The Introduction also describes the book’s structure, the organization of each chapter, and its contribution to anthropology.