Recent debates about the knowledge society have furthered awareness of the limits of knowing and, in turn, have fuelled sociological debates about the persistence and intensification of ignorance. In view of the ubiquity of the notion of ignorance, this paper focuses on Georg Simmel’s insightful observations about Nichtwissen (nonknowledge) as the reverse side of knowledge. The paper seeks to relate the notion of nonknowledge to Simmel’s conceptualization of objective and subjective culture. In Simmel’s view, modern society produces cultural objects in order to satisfy individuals’ inherent drive to become social beings. Ever more nonknowledge can be understood as an outcome of the growing difficulties in absorbing the achievement of objective culture into subjective culture. To illustrate the crucial importance of such a view of the unknown for today’s debates on the knowledge society, the paper uses illustrative examples ranging from the strategic acknowledgement of nonknowledge in personal relationships to public encounters and the right not to know one’s own genetic identity.