This chapter addresses the question of the “essence” of selfhood by examining different ways of construing its defining feature, viz. reflexivity or the self-relation. This, in turn, frames an ‘appropriative’ reading of Heidegger’s account of reflexivity. As the “Ur-phenomenon” of the self-relation, self-appropriation is not primarily an epistemic relationship to third personal, objective facts, but rather a practical relation to possibilities of existence that always already implies a simultaneous relation to self, other, and world. The kind of existential possibilities made available to Dasein and the ways in which they are appropriated, in turn, bear critically upon the question of both individual and collective emancipation. The central claim is that the self-relation must be understood from the holistic perspective of the interdependence of self, other, and world and, as a result, an adequate ontology of the self is possible only as a critical social ontology. Hence, the appropriative view is distinguished from predominating paradigms of Heidegger interpretation and its core features as an approach to social ontology are outlined to frame the reading of Volume One of Being and Time developed in the subsequent chapters.