¶ 6. The Task of Destroying the History of Ontology
All research—and not least that which operates within the range of the central question of Being—is an ontical possibility of Dasein. Dasein's Being finds its meaning in temporality. But temporality is also the condition which makes historicality possible as a temporal kind of Being which Dasein itself possesses, regardless of whether or how Dasein is an entity 'in time'. Historicality, as a determinate character, is prior to what is called "history" (world-historical historizing).1
"Historicality" stands for the state of Being that is constitutive for  Dasein's 'historizing' as such; only on the basis of such 'historizing' is anything like 'world-history' possible or can anything belong historically to world-history. In its factical Being, any Dasein is as it already was, and it is 'what' it already was. It is its past, whether explicitly or not. And this is so not only in that its past is, as it were, pushing itself along 'behind' it, and that Dasein possesses what is past as a property which is still present-at-hand and which sometimes has after-effects upon it: Dasein 'is' its past in the way of its own Being, which, to put it roughly, 'historizes' out of its future on each occasion.2 Whatever the way of being it may have at the time, and thus with whatever understanding of Being it may possess, Dasein has grown up both into and in a traditional way of interpreting itself: in terms of this it understands itself proximally and, within a certain range, constantly. By this understanding, the possibilities of its Being are disclosed and regulated. Its own past—and this always means the past of its 'generation'—is not something which follows along after Dasein, but something which already goes ahead of it.
This elemental historicality of Dasein may remain hidden from Dasein itself. But there is a way by which it can be discovered and given proper attention. Dasein can discover tradition, preserve it, and study it explicitly. The discovery of tradition and the disclosure of what it 'transmits' and how this is transmitted, can be taken hold of as a task in its own right. In this way Dasein brings itself into the kind of Being which consists in historiological inquiry and research. But historiology—or more precisely historicity3—is possible as a kind of Being which the inquiring Dasein may possess, only because historicality is a determining characteristic for Dasein in the very basis of its Being.
1 'weltgeschichtliches Geschehen'. While the verb 'geschehen' ordinarily means to 'happen', and will often be so translated, Heidegger stresses its etymological kinship to 'Geschichte' or 'history'. To bring out this connection, we have coined the verb 'historize', which might be paraphrased as to 'happen in a historical way'; we shall usually translate 'geschehen' this way in contexts where history is being discussed. We trust that the reader will keep in mind that such 'historizing' is characteristic of all historical entities, and is not the sort of thing that is done primarily by historians (as 'philosophizing', for instance, is done by philosophers). (On 'world-historical' see H. 381 ff.)
2 'Das Dasein "ist" seine Vergangenheit in der Weise seines Seins, das, roh gesagt, jeweils a us seiner Zukunft her "geschieht".'
3 'Historizität'. Cf. note 2, p. 31. H. 10 above.