Heidegger sought to peer behind Western metaphysics by engaging in the pre-theoretical conditions necessary for intentionality (representations of things) in human thought. That is, what does “to exist” or “to be” mean with regards to entities (beings); Heidegger refers to what makes beings intelligible (able to be represented) as the meaning of Being (not in the set of being). This ontological difference between being and Being (as not a super-being) is conflated in the story of Western philosophy since the time of Plato which equated the meaning of Being to a series of beings (namely idea, substance, monad, subjectivity, and will-to-power). Such a distinction is relevant as all categories of thought that do not clarify the ontological difference are subject to the limits of their mode of Being. Thus, the investigation of the a priori transcendental conditions for modes of Being is Heidegger’s preoccupation.
Heidegger begins with the the unique mode of Being for humans (Dasein) as “the having-to-be-open” or “Being is an issue for it”. This is to say that Dasein tends towards sense/meaning-making, to make intelligible. The phenomenological method for examining such tendencies is hermeneutic (interpretive) and historically embedded. Dasein begins with ordinary encounters with entities (equipment) through the their skillful use (readiness-to-hand). While engaged in the activity, Dasein lacks a conscious awareness of the equipment as an independent entity in the way that one would if standing back; the person is absorbed in the world with the equipment and so the person has no awareness of himself as a subject separate from a world of objects. This mode of encountering contrasts with scientific and philosophical activity where the senses are means to reflection and contemplation of context-free entities (present-at-hand). The transitory phase between these two modes of being refers to an un-readiness-to-hand where skilled activity is disturbed but remain phenomenologically near in context; a piece of broken equipment may still be adapted for use. Dasein is in (dwells) the world of beings in the ways that equipment are involved; the network of intelligibility or relational ontology is the totality of involvements with teleological “for-the-sake-of-which” ends; involvements are choices towards that end during which entities are made intelligible. Dasein’s place in the world of involvements is thus spatial in the sense of readiness-to-hand; entities are nearby if they are readily available for activity and far away if not irregardless of physical distance. The who of Dasein in this world is to be-with entities that can be encountered by the Other; what Dasein do is determined by “what one does” which is historically and culturally conditioned.
Dasein’s relation with the world can also be interpreted as “care” through the dynamics of “thrownness, projection, and fallen-ness” for unpacking “having-to-be-open” and temporality. Thrownness or having been thrown into the world is Dasein’s confrontation with the set of historically conditioned possibilities for acting (past). Dasein understands each possibility by projecting itself onto each possibility (future) according to its network of totalities. The realization of understanding is through skilled read-to-hand encounters (present). Fallen-ness is the loss of Being its Self (making things intelligible) through everydayness of the they (idle talk, search for novelty, and ambiguity). Thus, the authentic self seeks to find its own relation to other entities rather than be lost to the they. To discover such relations, Daesin can use the possibility of its own death (“possibility of the impossibility of any existence at all”) to disclose the negation of all its relation and so conversely discloses them. The authentic relation to death is one of anticipation rather than expectation where the latter is a fear (passive) that discloses only some beings in the world; the former “owns death” by using its possibility to affirm new relations and modes of Being.
Heidegger’s later works (after the turn) shifts Dasein’s mode of Being from temporality to that of dwelling; the subjectivity of Being from Dasein’s relation is abandoned in favor of the historical account of the unfolding of Being. The history of Being is now represented as transformations that have shaped Dasein’s intelligibility; human beings dwell between the earth and sky (nature) and before mortals and divinities (culture). The relationship with nature is poetic habitation rather than scientific (instrumental), culture requires an openness towards death and the possibility of paradigm shifts in intelligibility (new cultural templates). The latter is most relevant to the modern age of technological thinking where things are intelligible according to being enframed or “challenged” in order to produce something to be held in “standing-reserve” for use. Technology’s clearing (when things are revealed as mattering in some way) turns nature into resources to be extracted, stored, and ultimately exploited as a means to an end. The issue of technological thinking is its domination and the consequent forgetfulness of Being; enframing covers up the fact that technology is only one mode of making things matter, a single clearing rather than one of many possible modes of revealing (poiesis). Ultimately, Heidegger’s solution to realizing poiesis was through artisanship, attentive listening (tuning with rhythms of nature), and adopting a non-evasive attitude towards death.