Our conduct of the ontological investigation in the first and second parts opens up for us at the same time a view of the way in which these phenomenological investigations proceed. This raises the question of the character of method in ontology. Thus we come to the third part of the course: the scientific method of ontology and the idea of phenomenology. The method of ontology, that is, of philosophy in general, is distinguished by the fact that ontology has nothing in common with any method of any of the other sciences, all of which as positive sciences deal with beings. On the other hand, it is precisely the analysis of the truth-character of Being which shows that Being also is, as it were, based in a being, namely, in the Dasein. Being is given only if the understanding of Being, hence the Dasein, exists. This being accordingly lays claim to a distinctive priority in ontological inquiry. It makes itself manifest in all discussions of the basic problems of ontology and above all in the fundamental question of the meaning of Being in general. The elaboration of this question and its answer requires a general analytic of the Dasein. Ontology has for its fundamental discipline the analytic of the Dasein. This implies at the same time that ontology cannot be established in a purely ontological manner. Its possibility is referred back to a being, that is, to something ontical―the Dasein. Ontology has an ontical foundation, a fact which is manifest over and over again in the history of philosophy down to the present. For example, it is expressed as early as Aristotle's dictum that the first science, the science of Being, is theology. As the work of the freedom of the human Dasein, the possibilities and destinies of philosophy are bound up with man's existence, and thus with temporality and with historicality, and indeed in a more original sense than is any other science. Consequently, in clarifying the scientific character of ontology, *the first task is the demonstration of its ontical foundation* and the characterisation of this foundation itself.―from_The Basic Problems of Phenomenology_

~ Martin Heidegger

The *second task* consists in distinguishing the mode of knowing operative in ontology as science of Being, and this requires us to *work out the methodological structure of ontological-transcendental differentiation*. In early antiquity it was already seen that Being and its attributes in a certain way underlie beings and precede them and so are *a proteron*, an earlier. The term denoting this character by which Being precedes beings is the expression *a priori*, *apriority*, being earlier or prior. As *a priori*, Being is earlier than beings. The meaning of this *a priori*, the sense of the earlier and its possibility, has never been cleared up. The question has not even once been raised as to why the determinations of Being and Being itself must have this character of priority and how such priority is possible. To be earlier is a determination of time, but it does not pertain to the temporal order of the time that we measure by the clock; rather, it is an earlier that belongs to the inverted world. Therefore, this earlier which characterises Being is taken by the popular understanding to be the later. Only the interpretation of Being by way of temporality can make clear why and how this feature of being earlier, apriority, goes together with Being. The *a priori* character of Being and of all the structures of Being accordingly calls for a specific kind of approach and way of apprehending Being―*a priori cognition*.The basic components of *a priori* cognition constitute what we call *phenomenology*. Phenomenology is the name for the method of ontology, that is, of scientific philosophy. Rightly conceived, phenomenology is the concept of a method. It is therefore precluded from the start that phenomenology should pronounce any theses about Being which have specific content, thus adopting a so-called standpoint. ―Martin Heidegger, from_The Basic Problems of Phenomenology_

~ Martin Heidegger