Melissa Raphael presents a critical examination of the central contribution to the twentieth-century concept of holiness made by the German Protestant Rudolf Otto (1869-1937). Whereas Otto's work has usually been studied from a phenomenological perspective, this book is original in offering theological arguments for Otto's idea of the holy becoming an anchor concept of contemporary theistic discourse. This volume analyses the scholarly context that shaped Otto's concept of holiness and, finding that the theological significance of the latter has been overlooked, discusses the relation of the numinous and the holy to the divine personality, morality, religious experience, and emancipatory theology.