Miguel De Beistegui, in three long paragraphs at the beginning of his essay "The Transformation of the Sense of Dasein in Heidegger's Beiträge zur Philosophie (Vom Ereignis)" (Research in Phenomenology 35), does a good job of summarizing what Heidegger's questions on ontology are all about.

At the heart of being lies the following contradiction, which representational thought—metaphysics—has continuously and consistently overlooked: being “is” not; it is, literally, nothing. For “is” or “are” only those things—those beings—that can be represented, only those beings with a minimal structure of identity and permanence such that they can be identified and recognized by way of nouns, or substantives. In one way or another, beings are substances, or derived from substances, or attached and attributed to substances. Yet because “being” is not a thing, because it is no-thing, it is the one and most singular exception to the rule and law, as well as to the logic of substance, a rule and a logic that has come to permeate our use of language and of grammar to such an extent that being itself has fallen prey to it: being has been and continues to be mistaken for a substance and for the essence of what is. And yet, being is not simply foreign to this law and this logic; it is not simply foreign to those things from which it differs essentially. If it “is” indeed nothing, it is at the same time everything: it is the very operation whereby the things themselves come to be, the very operation whereby “there is” (something rather than nothing). Being is only in and through its difference from beings. And this, in such a way that one can wonder as to whether it is at all possible to ever speak of being “itself ” or “as such,” that is, independently of those beings which come to be in its wake, independently of those things that can be identified by way of nouns. Can there ever be being as such, if being is indeed such that it does not refer to an essence or a substance—a self-present and self-identical structure—and, at the same time, such that the very operation for which this word stands always opens the field of beings as such and as a whole? Can we ever speak of being itself, if being is such as to escape the structure of selfhood altogether? Since it is neither an individuated thing nor an essence, neither a substance nor an idea, it cannot be treated as a noun or made the subject of a proposition. It cannot take the form of the classical “S is P”; it cannot be made the object of a judgment of predication, whether analytic or synthetic. For any such proposition would presuppose and have decided in advance about that which is precisely at issue in the proposition regarding being: that being can have the status of subject in a proposition; that this proposition allows for a doubling of being as copula; that being can be predicated; that the matter for which the word “being” stands can be inscribed within an implicit understanding of language as propositional—all of this when the very operation of being is such as to resist any such subjectivization and copulation, and when the essence of language itself is addressed for the first time in and through this operation. This operation escapes the classical form of the proposition altogether, which understands being from a twofold perspective: first, and as its ontological presupposition, as the substrate, substance, or subject characterized by its permanence and identity beyond and despite the various transformations and changes it can be subjected to (recall the first analogy of experience in Kant’s Critique of Pure Reason), and thus, ultimately, as the idea, the eidoV, the essence or the origin and cause of such transformations; second, as the copula or the purely functional link uniting subject and predicate. As a result, when, attempting to develop a discourse about being, we say: “Being is . . .,” we already give the impression that it is a matter of predicating Being, about which a fundamental decision has already been made, the decision according to which it designates something, first of all, like presence, or actuality (ousia), and second, something like an essence (eidoV), or the being of a thing. We give the impression, then, that being refers to this twofold sense of substance-subject and essence first thematised by Aristotle. We have already inscribed the operation of being within the metaphysics of the ousia-upokeimenon, we have already answered the question regarding the status of being before having had a chance to raise it. Yet, despite all these difficulties, if the word “being” is not the emptiest and most general of words, if something is really at issue in it, it will need to be made the object of a certain discourse and take the appearance of a proposition, albeit at the cost of a radical transformation of the very nature of the proposition. Yet this discourse will need to unfold from the very matter for which the word stands, the proposition will be of being, that is, belonging to being, in the strictest and most literal sense. What, then, is the proposition of being? What form must this ontologic take? What must now be the sense of logoV, if it is no longer compatible with its classical conception as logical proposition?

Continued.  ¶ 9:33 PM