The essay deals with the understanding of the two key concepts from Sein und Zeit (SZ) mentioned in the headline, including a debate on the issue of das Man in Inquiry: an Interdisciplinary Journal of Philosophy. It is noted that reading SZ involves being simultaneously written by the work in a process of reciprocity; this entails a questioning of alleged possession of this or any work, it having been made accessible to the public by its publication.Das Man, as a concept for inauthenticity, needs a counterpart for authenticity, which in SZ is provided by Eigentlichkeit, Self-ownership.This comes into existence via ?being-towards-death?, where the caring being, as a being of possibilities, encounters its ultimate possibility death which is also the end of possibilities.The Inquiry debate, the main contenders of which were Hubert Dreyfus and Frederick Olafson, hinges on the question whether das Man should be understood primarily as ?at bottom a deformation of Mitsein? (Olafson) or ?the conformity necessary for the institution of collectively intelligible social practices (Dreyfus, in the words of his advocate in the debate, Taylor Carman). Both sides, however, give evidence of misreadings of SZ of a kind that call for an explanation. The proposal is that this could be given in an analysis of such a rhetoric of polemics that transforms SZ into a state of Vorhandenheit when making it an object of investigation by the contenders rather than such a tool for being-changed that is mentioned above.The relation between the two aspects of das Man, as oppressive know-all or as forms of established truth for Dasein, remains unsolved, however.