Being is the ontological ground of what is. Being is the primary or primordial onto-logical reality. Anything that-is is some sort of quality or expression of Being. Yet Being (as such) is never found in pure isolation or in a pure independence, since Being is always discovered as Being-in-existence. Being is what-is, and what-is reveals itself, yet every revealing or presencing of Being can only be experienced and interpreted within a context of meaning provided by one's existential context - the physical and social context, or what can be called world existence.
Who am I? This self-being, for Heidegger and existentialists, has no apriori or subsistent essences, no necessary or fixed attributes in itself. It is colorless, so to speak, nothing there except [i suppose..] Being's urge to reveal itself. But other than this urge, Being has no set of ideals or plans or characteristics. [Heidegger did not accept the Platonic notion of a soul entering into the physical world (or in dual relation with this world) carrying a set of fixed ideas or essences in itself]. Likewise, Being on the grander scale could well be equated with the God-Reality, yet this would not be a God with subsisting essences, but rather a God empty of any fixed ideas or ideals - except the basic urge to express. This seems problematic, for we would then ask what is coming forth from Being if Being is empty of essences.
The answer might be that Being emerges as-it-does in response to individual or particular circumstances, though this is not to deny the fact of common human circumstances - which provide ground for common human experiences. In other words, the expression of Being is dependent on or conditioned by the existential-situational context of any particular. Each living situation, ie. each person, which is Being-there (at the very centre of Being-in-expression), provides the coloring of Being. As the person authenically responds to his overall situation, there is how Being expresses. Being manifests in various ways of being-in-the-world. For example, one basic mode of responding/expressing is care, as Being feels its interconnectiveness and mutual dependence with the social and ecological context, and thus the felt need to care. Being is realizing itself in-the-world, in an existential context, which is the only place that Being CAN realize itself. That is, Being cannot realize itself or know itself in some spiritual dimension isolated-alone from the physical/social existence.
How Being reveals itself is fully dependent on the conditions of its existence, that is, in relation to the concrete existence in which we find ourselves - the conditions of our surrounding world, our body needs, our social fabric, and our temporal existence as individuals. Being is only known as Being-in-existence or Being-in-a-world. We only know Being (Reality) from our subjective in-it situation. All that we can know of Being is from 'Being-there', that is, we only know Being from our circumstantial perspective, our being-in a place/time of existence. Everything and every experience is an emergence of Being, yet what we realize about Being, and in fact how Being emerges (as qualities), is circumstantially colored. Qualities of Being emerge as they do, in the way they do, because of existential circumstances. So we are not privy to knowing Being-in-itself, nor is there actual content(fixed essences) to Being-in-itself (except the infinite possibilities of Being).
Heidegger also denies that Being is like a thing or separate substance, also denying that self is like a thing. Instead, Being is a process, though not like the Hegelian World-Process of the Grand Idea/Truth seeking comprehension and completion. The Process is more like a Mystery unfolding, without any preconception of what may or should unfold. Being-as-Presence is not a static Presence, nor a Grand Spiritual Entity, nor the Great Encompassing Idea; but rather, it is an eternal Presencing (verb, in action), emerging and revealing, but not 'from' a fixed God-Entity. It is more like something coming from Nothing. Thus, Being is dynamic movement, unfolding experience, and surprise. It is not a something to think 'about' but rather, Being reveals itself through our openness - letting Being think and experience through us. Being, as dynamic activity or presencing, is thus known only through experience or direct apprehension, not by the thinking mind trying to reason what it is.
For Heidegger our only authenic recourse is to be open to Being, awake to how Being reveals itself (in this particular place/time). This authenic approach to Being, to who we are and what is reality, can be contrasted by the inauthenic approach of denying what is sincerely revealed as self-evident (in terms of oneself or the world) and merely imitating the beliefs, ideals or behaviors of others or society or religions. Authenic being is being true to oneself and to make one's own conscious decisions of how to be and what to accept as reality. It is to live from the centre of one's own revelation, or how Being reveals itself to me, and to freely choose my way of being-in-the-world. Also, authenic openness is to face our own reality and the outer reality with courage to see it as it is, without pre-intent or preconceptions, letting Being reveal itself as it is and facing this given situation of being-in-existence. Inauthenic being is inventing beliefs (or accepting other's beliefs) which suppress the facing of what is most apparent in ourselves and in the world.
What is important is the openness - without preconceptions and an attempted independence from social conditioning. There is no possible knowledge of God except in how Being presents itself, and an authenic knowledge/understanding of God can only be from how Being reveals itself to us.
This authenic openness to Being, as it is revealed, can be viewed as openness to God, for Being here is equivalent to God. Now the reason I say that Being can be equated to God is that Being IS the primordial ontological reality and so the universe (including man) can only be the expression of God/Being. Yet this is not a God directing the human, nor a God with some sort of plan.
The openness to Being would be true worship. Openness to Being is a worship kind of relationship to what is Greater. In one sense Being is who we are and in process of revealing, while in another sense Being is beyond us in its totality of ontological Substance, so we are engaged in a relationship with Being as a mystery Greater than any limited understanding. Our only true recourse is to be open to Being (or God), open to what is being revealed as authenic and true, which can be equated with worship. Then, we must make decisions in life and affirm beliefs that are in accord with how Being reveals itself to us. This is being directed from within, directed from an inner revelation of Being (which is God), God spontaneously emerging.
Lastly, it seems a debatable question whether Being has, in itself, subsistent essences or directives. The usual existentialist position would seem to deny it, taking a contrasting view that Being has no directive other than to Be, and that each [human] authenticity rests upon their self-created directives or decided ethics, which is the very act of Self/Being creating itself in this existence. Thus, I suppose there are two poles of understanding 'the existential situation', with Neitzche and Sarte on one side proclaiming the emptiness of Being and thus a self-freedom, while Keirkegard and Jaspers upholding a sense of needed relationship to a Source of Being beyond us, and Heidegger who seemed to be in an ongoing questioning and discovery of the mystery of Being. Maybe its like the saint on one side who is in surrender, while the magician on the other side is creating, so I wonder if there is a middle place of reconciliation.
The existentialist (and post-modernist) ideal is to be freely creative, to virtually create one's own ideals, values, ethics, and even interpretation of reality; within a realization that there are no Objective values in the reality of which we live. This appears to be a polytheistic religion with no vertical dimension (of a higher vs. a lower). Yet for Heidegger there does seem to be an objective ideal, or at least an authenic one, which is to open and true to Being-presencing. This is viewed as Being responding to existence, or say Being presencing or expressing according to the contextual needs of this existence.
Following further with this view, it might be proposed that the responding qualities of Being (traditionally thought of as qualities inherent in God) are made up right here in this physical/social existence as a response to circumstance and need, (rather than being pre-subsistent in divine Being). That is, we actually invent those qualities which were traditionally believed as subsistent in God, or say, those qualities creatively emerge (from the possibilities of Being) due to our awakening in this existence/world and the needs here. And thus, creation is an ongoing process unfolding from this very world, rather than unfolding from a Super-Entity God. Though God could be reinterpreted as the Being-of-possibility, with creation as the ongoing creation of qualities and virtues in response to the everchanging existential context.
Nonetheless, it can be argued that this existentialist metaphysics still implies some presupposed or inherent essences of Being: such as an urge to express, to feel, to know, to respond, and even to care, or to create beauty, order, justice. These essential qualities of our being, (and thus of Being-as-such), might well be regarded as givens, predispositions, and ultimately as inherent-subsistent qualities of Being (and thus of God as The Primordial Being) -- for it is certainly debatable whether these very basic qualities (at the motivational spring of our being) can be fully caused (and explained) by mere existential givens. Maybe the truth is in a reconciling relation between these theistic and existentialist understandings of reality.
The implicit ethical ideal for Heidegger is being authenically 'there', 'being-there' authenically and with full consciousness. This concept of being-there (Dasein), what man is meant to be, might just as well be translated as being-here, fully present here, in this existential situation. And this means being open, authenically open to the realities of the world and to how I am in this world. This openness accepts such reality just as it presents itself, without logically altering the appearance of reality to suit some ulterior [inauthenic] aim. So the ideal is be open and present in a foremost pre-logical manner, understanding the way things-are in a raw, intuitive, feeling sense, which then become the givens/premises for any subsequent reasoning or theorizing.
Rejected is the idea that reality/being can be known by a impartial observer seeing Being (or Reality) from a distance, as in the subject/object model. Consciousness cannot acquire its own absolute transcendence from observations, as though seeing reality (of oneself or the world) from an objective distance. Rather, consciousness is always embedded in the world-existence. But Heidegger does not view this negatively or as a skeptic of knowledge. Instead, true knowledge IS possible, though knowledge is always an understanding of how one is IN the world, or it is knowledge of how the world presents itself to the embedded consciousness.. being-in-the-world. So our knowledge of reality/existence is, and can only be, from being-in-the-world. Our knowledge of anything (inner or outer) can only be from living-within that which we seek to understand.
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Openness to Being can be interpreted as openness to God, since it is openness to the Greater Reality. This greater Being/Reality reveals itself to us and even speaks to us through our authenic conscience. Yet Heidegger is not suggesting a traditional notion of God as outside of this world/existence. The Being revealing itself in conscience is none other than our true self. Though this Being, as true self, is monistic and common to all, not distinct from others. It is the human being. Yet this being does not hold a hypostatic existence separate from our world-existence. In other words, Being is not a 'something' trying to manifest itself. Rather, Being is the dynamic energy of expression. What being is is the expressing itself, the presencing, and how this manifesting-expressesing actually occurs depends ultimately on the existential context in which conscious-authenic human-being (Dasein) finds itself. So conscience and expression depends on how being-is in the world. There is only one conscience - human conscience, just as there is only one Being; yet conscience may guide each somewhat differently, since each particular consciencing is in response to somewhat unique situations.
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Taking Heidegger to a more religious view, we can equate Being with God. Yet God, in this view, is not a Super-Entity with qualities and intents that we are meant to imitate. There is no such God, and so the ideal is not to imitate or even to reflect a Super-Existence separate from ourselves. Instead, God is the emergencing of possibility through man. God is emptiness in process of becoming, and unconsciousness becoming conscious. God/Being is only really known through man.