Concise Statement of Dasein's Essence
[T]o exist as Da-sein means to hold open a domain through its capacity to receive-perceive the significance of things that are given to it and that address it by virtue of its own "clearing".I will address each part of the quote in turn.
Zollikon Seminars, 4/H4.
"To hold open a domain": Dasein, as being-in-the-world, is always already holding open a world. The active nature of 'world-opening' was recently accentuated to me by a statement by Merleau-Ponty in The Primacy of Perception: "We must say that at each moment our ideas express not only the truth but also our capacity to attain it [i.e. the idea] at that given moment" (21). To be able to think implies the opening up of a particular world wherein that thought is meaningful and, hence, possible; to be able to speak meaningfully, then, is to remain in (or sustain) an opened domain at the time one is thus thinking. We see the tight relation between ideas and the opened world in various phenomena: when someone says something in one domain that we are not presently open to, what they say is alien, enigmatic, or perhaps humorous when situated within our current domain. So it is a matter of remaining within an open domain and, indeed, having a grasp of when particular domains are relevant and/or appropriate for our context. Either way, to be Da-sein is to actively "hold open a domain."
"Through its capacity to receive-perceive": as the being that is in-the-world and that dwells in its openness (Offenheit), Da-sein has a capacity to "receive-perceive" (Vernehmen-können) things. Heidegger uses this term to differentiate it from the psychological approach of "seeing [things] in a sensory fashion with the eyes" (ZS, 35/H44). In relation to perception, Heidegger has been quite clear: first and foremost we see beings, things, not bare sensations. The dominant psychological theory of perception requires a distinction between sensation, understood as bare sensory stimulation, and perception, understood as the cognitive ordering of sensations into meaningful objects. Whatever may be said of the physics and physiology behind this understanding of perception, it is not primarily where human beings dwell and insofar as psychology is the study of human beings it must be grounded in an understanding of the human mode of being if it is to be relevant.
The capacity to "receive" speaks of the relation between Da-sein as the opening and beings as that which comes into the open. The metaphor of the open can be easily misunderstood: Da-sein's openness is not merely present-at-hand such that it passively sits and waits for things to be deposited in it, like an empty box that we use to store things. Rather, Da-sein's openness, as constituted by practices, attunements, and a totality of inter-involved beings, is more like a filter that polarizes the world such that beings that are relevant to my current projects may appear if present.
While the opening is not a present-at-hand thing, similarly it is not a subjectivistic attribution of value and meaning onto a meaningless objective thing. As Heidegger states in the "Letter on Humanism," man does not unilaterally decide how beings appear, but it is always a question of man creating and sustaining an opening appropriate to the kind of beings that man is concerned with (paraphrase; Basic Writings, 234). This "receiving" is particularly important in relation to the "given to it" in the original quote, to be addressed below.
"To receive-perceive the significance of things": as early as Being and Time, Heidegger claims that we first see the significance of things for our projects, according to our world, not the thing itself with its present-at-hand properties. We are ecstatically open to beings because we care about things, thus they can appear in a significant and meaningful way (in the least as either relevant or irrelevant for our concerns). For a being who literally "does not care," things would not appear as things. This would be the highest expression of the so-called "objective" viewpoint where, at best, one would see bare sense data if one would not simply be catatonic and thus not 'see' anything at all. But Da-sein does not exist in such a state; even in the case of depression, where all beings and events get reduced to the same meaningless level, our mode of being-in-the-world is a deficient mode of concern, not the absence of concern. That we first and foremost see significances, rather than bare sense data that must be constructed into meaningful things, is one of Heidegger's great insights.
"Things that are given to it": things are "given" to Da-sein. As in "Letter on Humanism," man does not force beings to appear, does not bring them to presence by mere force of will; they are gifts. Being is that which gives, es gibt (it gives). Man creates and sustains the opening by way of his cares and concerns, thus giving a space for being to enter in; being gives that which man can bring to presence given his concerns, yet essentially exceeds that presence. This is the clearing where the event of appropriation (Ereignis) occurs: man's opening and being's giving, both of which are co-necessary. Technology is a danger because it forgets this receiving/giving, uncovering/covering, but sees things as merely present resources that are only available as resources. The same may be said for every appropriation: when our concern is appropriately interacting with beings, the way in which beings come to presence (as the dynamic relation between presence/absence) will be covered over and necessarily so. When our concern is getting about in the world, the mode of presencing cannot be of concern; the latter is necessarily reflective in nature and must be its own matter of concern. Philosophy, as fundamental ontology, brings Ereignis to remembrance.
"And that address it": in the realm of technology "man [is] the master of being" ("The Turning," in Question Concerning Technology, 39). Being is the mere presence of endlessly interchangeable materials that are understood through man's calculating concerns, that exist solely for those concerns. In this view, beings cannot "address" Da-sein since beings are merely present as materials. When Da-sein properly dwells, however, beings address man as this particular being in this particular context with this particular use. Mark Wrathall put it well:
Rather than increasing the universal and uniform availability of everything, we need instead to learn how to let things be things rather than resources, and develop practices attuned to the things that are peculiar to our local world with their own particular earth, sky, mortal practices and divinities.Beings must condition us in their particularity rather than us merely conditioning them as resources for our own concerns. We should let them address us as much as we address them.
How to Read Heidegger, 111.
"By virtue of its own 'clearing'": I have yet to discover if Heidegger is using "opening" and "clearing" as synonyms, but this part of the quote re-emphasizes the human aspect of being-in-the-world. Heidegger often uses the word Geschick in reference to man's clearing. The common translation is "fate" or "destiny" (see above reference to "Letter on Humanism"), but it can also mean "skill," "aptitude," or "aptness." Man's clearing sets the stage wherein beings can appear as meaningful; it, in a sense, sets up in advance (makes fateful) the possibility of beings appearing within a particular world. But this is also skillful insofar as our worlds are constituted by practices of which we must gain aptitude, whether at an everyday level or as masters. Similarly, these practices must be enacted appropriately; they must be properly geared to our current context such that we are not enacting, say, a world of competition when we should be enacting a world of care or love. Beings, if they do appear, appear by virtue of man's clearing a space for them to appear (and by virtue of being's gift of being).