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

There appears to be a fifth way, that of eminence. According to this I argue that it is incompatible with the idea of a most perfect being that anything should excel it in perfection (from the corollary to the fourth conclusion of the third chapter) . Now there is nothing incompatible about a finite thing being excelled in perfection; therefore, etc. The minor is proved from this, that to be infinite is not incompatible with being; but the infinite is greater than any finite being. Another formulation of the same is this. That to which intensive infinity is not repugnant is not all perfect unless it be infinite, for if it is finite, it can be surpassed, since infinity is not repugnant to it. But infinity is not repugnant to being, therefore the most perfect being is infinite.The minor of this proof, which was used in the previous argument, [1] cannot, it seems, be proven *a priori*. For, just as contradictories by their very nature contradict each other and their opposition cannot be made manifest by anything more evident, so also these terms [viz. being and infinite] by their very nature are not repugnant to each other. Neither does there seem to be any way of proving this except by explaining the meaning of the notions themselves. Being cannot be explained by anything better known than itself. Infinite we understand by means of finite. I explain infinite in a popular definition as follows: The infinite is that which exceeds the finite, not exactly by reason of any finite measure, but in excess of any measure that could be assigned.—[2] The following persuasive argument can be given for what we intend to prove. Just as everything is assumed to be possible if its impossibility is not apparent, so also all things are assumed to be compatible if their incompatibility is not manifest. Now there is no incompatibility apparent here, for it is not of the nature of being to be finite; nor does finite appear to be an attribute coextensive with being. But if they were mutually repugnant, it would be for one or the other of these reasons. The coextensive attributes which being possesses seem to be sufficiently evident.—[3] A third persuasive argument is this. Infinite in its own way is not opposed to quantity (that is, where parts are taken successively); therefore, neither is infinity, in its own way, opposed to entity (that is, where perfection exists simultaneously) .—[4] If the quantity characteristic of power is simply more perfect than that characteristic of mass, why is it possible to have an infinity [of parts] in mass and not an infinite power? And if an infinite power is possible, then it actually exists (from the fourth conclusion of the third chapter).—[5] The intellect, whose object is being, finds nothing repugnant about the notion of something infinite. Indeed, the infinite seems to be the most perfect thing we can know. Now if tonal discord so easily displeases the ear, it would be strange if some intellect did not clearly perceive the contradiction between infinite and its first object [viz. being] if such existed. For if the disagreeable becomes offensive as soon as it is perceived, why is it that no intellect naturally shrinks from infinite being as it would from something out of harmony with, and even destructive of, its first object?—from_A Treatise on God as First Principle_, 4.63-4.64

~ John Duns Scotus