>>24498983 (OP)1.) We have forgotten to investigate what the very meaning of Being is; and,
2.) Crucial to an investigation of what Being itself is (fundamental ontology, the deepest or most primordial basis of all possible thinking), is an investigation of our own form of being; in other words, he’s also saying that we (for the most part) have also forgotten our own being is the only means through which we have access to Being at al, and hence our own being (personhood) should be also be investigated, and this is a unique form of being different from that of, say, a rock or chair, objects we (conventionally) take as simply existing in a world external to ourselves. So, crucial to the investigation of Being, is the investigation of the being for whom Being can be an issue at all. Ontology necessarily intertwines with phenomenology, they cannot be extricated. Hence his investigations are both ontological and phenomenological.
Highly condensed form, from what little I understand. This basis also informs his investigations of concepts like time, society or our social life, as well as the history of philosophy or thought at large, what influences they still have on us today and also what parts have been as if buried or covered over, or at least their justifications and the full reasoning behind them have, even while we subconsciously carry on those conclusions, which we (for the most part) did not necessarily fully think through but simply had passed down to us: