The aim of this paper is to show, based on Heidegger’s ontology of being and Husserl’s ontological aspects of phenomenology, the ways in which may be highlighted the ontological turned epistemological (and vice versa) enigma of the actual presence of being-in-the-world. In such perspective the content of the philosophical term ‘being there’, in the sense of an original presence in the actuality of the world, is the key issue of discussion both in terms of the ontological implication of the accompanying (...) notion of transcendence and the epistemological relevance it can have by virtue of a phenomenon within the world. Concerning the latter in particular, except for some prompts from formal-mathematical theory, a special attention is drawn to the incompleteness of quantum theory with regard to the treatment of certain ‘ontological’ aspects of the measurement question in a quantum context. The clarification of certain epistemological ‘black box’ cases as this one by virtue of a subjectively based interpretation of the ‘being there’ is a main goal of this article as well as the ontological foundation of the ‘being there’ per se. (shrink)