This chapter critically reconstructs the core commitments of the appropriative view as a critical social ontology and, in the process, distinguishes between the essential and incidental aspects of fundamental ontology as an emancipatory project. First, ‘appropriation’ is governed by a second-personal logic of addresser/addressee: my existence is mine to appropriate in one way or another only because it always already addresses me in meaningful way and calls for a response. Second, Heidegger’s “unity thesis” implies that that self, other, and world are mutually interdependent, irreducible parts of a whole such that reification and/or alienation in one infect the others. This implies that it is not possible to have an authentic self-relation without an authentic—free and individualized—relation to others and the world. Third, the philosophical and emancipatory import of Heidegger’s tripartite distinction between ‘inauthentic’, ‘authentic’, and ‘undifferentiated’ modes of existence is articulated. The undifferentiated mode, which is neither authentic or inauthentic, helps to avoid pathologizing the social in advance, thereby leaving the necessary freedom for individuals to appropriate these structures in light of their concrete, socio-historical conditions. Hence, I introduce what I have called Heidegger’s ‘social difference’ between society and the social, which is the cornerstone of his post-foundationalist social ontology: the former refers to the ontic-empirical level of concrete societies and the latter to their ontological features.