To give an example, what is philosophically primary is neither a theory of the concept-formation of historiology nor the theory of historiological knowledge, nor yet the theory of history as the Object of historiology; what is primary is rather the Interpretation of authentically historical entities as regards their historicality.1 Similarly the positive outcome of Kant's Critique of Pure Reason lies in what it has contributed towards the working out of what belongs to any Nature  whatsoever, not in a 'theory' of knowledge. His transcendental logic is an a priori logic for the subject-matter of that area of Being called "Nature".
But such an inquiry itself-ontology taken in the widest sense without favouring any particular ontological directions or tendencies-requires a further clue. Ontological inquiry is indeed more primordial, as over against the ontical2 inquiry of the positive sciences. But it remains itself naive and opaque if in its researches into the Being of entities it fails to discuss the meaning of Being in general. And even the ontological task of constructing a non-deductive genealogy of the different possible ways of Being requires that we first come to an understanding of 'what we really mean by this expression "Being"'.
The question of Being aims therefore at ascertaining the a priori conditions not only for the possibility of the sciences which examine entities as entities of such and such a type, and, in so doing, already operate with an understanding of Being, but also for the possibility of those ontologies themselves which are prior to the ontical sciences and which provide their foundations. Basically, all ontology, no matter how rich and firmly compacted a system of categories it has at its disposal, remains blind and perverted from its ownmost aim, if it has not first adequately clarified the meaning of Being, and conceived this clarification as its fundamental task.
Ontological research itself, when properly understood, gives to the question of Being an ontological priority which goes beyond mere resumption of a venerable tradition and advancement with a problem that has hitherto been opaque. But this objectively scientific priority is not the only one.
1 '... sondem die Intepretation des eigentlich geschichtlich Seienden auf seine Geschichtlichkeit'. We shall translate the frequently occurring term 'Geschichtlichkeit' as 'historicality'. Heidegger very occasionally uses the term 'Historizität', as on H. 20 below, and this will be translated as 'historicity'.
2 While the terms 'ontisch' ('ontical') and 'ontologisch' ('ontological') are not explicitly defined, their meanings will emerge rather clearly. Ontological inquiry is concerned primarily with Being; ontical inquiry is concerned primarily with entities and the facts about them.