Heidegger distinguishes between the ontological inquiry of Being and the ontical inquiry of the positive sciences. The former lays the foundations for the latter, so not exactly 'mergeable' in this case.
¶ 3· The Ontological Priority of the Question of Being
. . . Basic concepts determine the way in which we get an understanding beforehand of the area of subject-matter underlying all the objects a science takes as its theme, and all positive investigation is guided by this understanding. Only after the area itself has been explored beforehand in a corresponding manner do these concepts become genuinely demonstrated and 'grounded'. But since every such area is itself obtained from the domain of entities themselves, this preliminary research, from which the basic concepts are drawn, signifies nothing else than an interpretation of those entities with regard to their basic state of Being. Such research must run ahead of the positive sciences, and it can. Here the work of Plato and Aristotle is evidence enough. Laying the foundations for the sciences in this way is different in principle from the kind of 'logic' which limps along after, investigating the status of some science as it chances to find it, in order to discover its 'method'. Laying the foundations, as we have described it, is rather a productive logic—in the sense that it leaps ahead, as it were, into some area of Being, discloses it for the first time in the constitution of its Being, and, after thus arriving at the structures within it, makes these available to the positive sciences as transparent assignments for their inquiry.1
To give an example, what is philosophically primary is neither ạ 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.2 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 ontical3 inquiry of the positive sciences. But it remains itself naïve 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. (Being & Time, H.10 & H.11)