Heidegger’s rejection of the presence-at-hand (Vorhandenheit) as the predominant mode of being that Dasein encounters in its being-in-the-world (In-der-Welt-sein) – its spatiality of being-in (In-sein) – has a deep implication for the integration of hermeneutics into philosophy. This is because Dasein is, by its very definition, a being that has comportment towards being (Seinsverhältnis). Dasein simply cannot exist in isolation and in indifference. Unlike Husserl before him, Heidegger reinterprets “intentionality” in terms of the spatio-temporality of Dasein‘s being-in, namely in its fundamental relatedness to the “worlding” (Welten) of the world. Worlding is what makes the world being, and not nothing. It is a fundamental-ontological form of clearing (Lichtung) of being in that it discloses in an irreducibly primordial way how and what being is: being-in.
It is in this light that Heidegger’s contrasting of presence-at-hand with ready-to-hand (Zuhandenheit) is to be understood. Instead of advocating an instrumentalist theory of existence, what Heidegger wants to achieve is to demonstrate that Dasein fundamentally relates to beings in ways that it can relate to them. In other words, to be confounded by a being is a sign that Dasein cannot relate to that being. Dasein relates through understanding, which is enabled by interpretation, i.e., making sense of something or making something intelligible, in an unceasing movement between the part and the whole that constitutes the hermeneutic circle of the fundamental phenomenon of understanding (Verstehen). In essence, ready-to-hand makes possible what Gadamer describes as prejudice (Vorurteil) in understanding and as something not to be methodologically rejected. Coincidentally, or perhaps synchronistically, this is also the position of quantum physics, which holds that time makes any methodological ignoring of the input of the observer as nonsensical. That Heidegger was in fact drawn to the contemporary advances in quantum physics only serves to illustrate the fundamental affinity between the hermeneutic thinking of phenomenological philosophers and the quantum insights of the new generation of scientists. Indeed the phenomenological turn in philosophy during the early 20th century heralded a holism of human thought never before seen in the long Western tradition of metaphysics: the being-in of the possibility of thinking as such.