There is a double meaning in the name of this thesis. This duality emerges from how the term ‘hermeneutics’ can be applied. In one sense the hermeneutics of this thesis is a textual interpretation of the philosophical history of ontology. This is an interpretation of ontological theory from its genesis with the Pre-Socratic concern with the ‘question of being’ and onwards through its salient historical developments up until the early twentieth century. The thesis interprets these developments as nevertheless maintaining a foundational understanding of ‘being’ as ‘quiddity’ or ‘what-ness’. While the ontological tradition diverges over disagreements about ‘realism’, ‘idealism’, or ‘nominalism’, for example, these disagreements are interpreted as having an unchanging understanding of ‘being’ in terms of ‘what-ness’ that unites them. Furthermore, this traditional understanding of ‘being’ as ‘what-ness’ is documented as having an implicit connection to a conceptual model of human understanding that divides the knowing subject from the known object. In opposition to a prominent interpretation that identifies this model as a Cartesian development, it is rather presented that it has roots that can be found within the philosophy of Plato. Moreover, this model is interpreted as being contingent on the technological development and adoption of literacy that predicated an emergent and reflexive understanding of the ‘what-ness’ of the self-subject.
However, this textual hermeneutics of the history of ontology also presents the challenge to understanding ‘being’ as ‘what-ness’ that occurred in the early twentieth century. This is found in the philosophy of Martin Heidegger, and in particular in his treatise Being and Time. This alternative understanding of ‘being’ is interpreted as presenting an ontology of ‘how-ness’. This understanding of ‘being’ as ‘how-ness’, as opposed to ‘what-ness’, is presented through Heidegger’s introduction of the concept of the ‘ontological difference’. This concept, it is shown, enables Heidegger’s understanding of human existentiality as self-interpretation. In addition, the inheritance of this ontological thesis of self-interpretative existence is traced from its phenomenological, hermeneutic, and existentialist roots. This includes the analysis of the ideas of such scholars as Friedrich Schleiermacher, Wilhelm Dilthey, and Edmund Husserl. Through documenting this provenance, the duality of this thesis’ title is demonstrated. It is not only a textual hermeneutics that is presented in this treatise, but also an example of hermeneutic phenomenology. Hermeneutic phenomenology, as Heidegger argued, is presented as the methodology for an ontology that understands human existentiality as self-interpretative. This methodology is analysed, and differing interpretations of its processes are critiqued. Furthermore, by interpreting human existentiality as hermeneutic, Heidegger’s understanding of ‘being’ as temporal is elucidated. The thesis of the temporality of human existentiality is then explained in terms of its structure as ‘being-in-the-world’. The equiprimordial characteristics of ‘being-in-the-world’ are analysed, such as ‘who-ness’, ‘there-ness’, and ‘world-ness’, and these are shown to together constitute human existentiality. The thesis then concludes by demonstrating how this hermeneutic phenomenology of ontological ‘how-ness’ also enables the explication of the temporality of technological existentiality