Perhaps the earliest signs of the growing autonomy of European thought even from within the Scholastic and ecclesiastic ranks became discernible with the Summa of Saint Thomas Aquinas which were to inspire the Scholasticism of the Middle Ages – so much so that it is possible to discern the most advanced developments of modern European philosophy in the writings and thoughts of the religious scholars at the turn of the first millennium. As early as his doctoral thesis on Duns Scotus, Heidegger decries and bemoans the crushing weight of scholastic tradition – Hellenistic and ecclesiastical – on the thought of the Middle Ages – “the absolute devotion and submission in temperament to the material that was known to be handed down by tradition” (ibid., p.9). The rationalist equiparation of the real with the rational, this Platonic realism where universals assume an ethereal status categorically distinct from their mundane particulars is precisely what the skeptical nominalist mediaeval philosophers disputed first – and perhaps what first induced Heidegger toward the critical pursuit of Aristotelian and Hegelian metaphysics as presaged by Scotus (v. Gadamer, ‘Platon’ in Les Chemins de Heidegger).
Mediaeval man is not in a modern sense with himself – he sees himself as always suspended in metaphysical tension. Transcendence restrains him from a purely human attitude in the face of the whole of reality. Reality as reality – as real world-about – is for him a constraining phenomenon in that it immediately and constantly appears as dependent on and measured by transcendent principles….and by the problems of the suprasensory. (Heidegger, D. Scotus, pp.10-11)
Tradition, transcendence and the suprasensory: Scholastic philosophy moves constantly away from the particular toward the general and then the universal through a process of deduction as opposed to induction, and imposes thus the rules of formal logic and grammar as a straitjacket on reality from which it seeks to deduce the univocity of transcendental being. It is not the case, claims Heidegger, that universals must be founded on particulars – psychologism -, but rather that universals cannot inform us or enlighten us as to reality and existence. This avulsion of the notion of Being from that of Substance arises already in the Middle Ages in the work of Duns Scotus where the timeliness of Being, its materiality in the sense of historicity or temporality, is distinguished from the transcendent time-less-ness or eternity of the Deity, of God. Already, Aristotle’s notion of ens – the physis of Being, its transcrescence through time – had opened the path to a conception of Being that could prescind from its sub-stance, its hypo-keimenon, - what subsists through the becoming of Being, its essence. (Franz Brentano had earlier drawn attention to the Greek philosopher’s “several senses of Being” in the Metaphysics, cf. his On the Several Senses of Being in Aristotle. Brentano was well known to Heidegger - see H. Gadamer’s frequent discussions of this in his lectures on Heidegger.)
Before Duns Scotus, Scholastic learning had confined the study of divinity to theology and faith; any philosophical theories of the Deity hinged on analogies and on revelation or on deductive logic. The Doctor Subtilis, as Scotus became widely known, was the first to devise and insist on a proof for the existence of God based on rational metaphysical speculation – not on revelation or formal syllogistic logic, or on mere analogy, but on dialectical reasoning and empirical induction. By so doing, he extended the scope of logic and metaphysics to the study of divinity and, more harmful to Scholastic doctrine, relegated the role of divine Revelation and of theology and faith to an inferior echelon of scholastic learning and epistemological inquiry. But even within the ambit of rational metaphysics Duns Scotus introduced a further distinction between a syllogistic logical deduction based on empirical observation and generalizations asseverated by the natural intellect – which he called logica practica - and the deductions dictated by the pure dia-logical or dialectical powers of the intellect. Scotus bases his argument for the existence of God from intellectual or conceptual extrapolations that emerge from the common qualities of observable appearances.
La méthode de philosopher de Scot est donc, comme celle de saint Thomas, comme celle de tous les péripatéticiens, ouvertement a posteriori, prenant son point de départ dans l'observation des faits. Mais l'ordre d'exposition des scolastiques est inverse de cette méthode, (E. Pluzanski, Essai sur la Philosophie de Duns Scot, p.39).
From the very reality of the intellect (cogitare), Scotus infers the certainty of being - not, and this was Descartes’s fateful error, that of the Ego! This schism between the sphere of the Divine, encapsulated in the logical rationalism of Scholastic theology, and that of the Natural, exemplified by the growing empirical skepticism of heretical natural philosophy, was intensified further in the new nominalist logic of William of Ockham. It represented a move away from universalizing theory to particularizing practical observation. Crucially, theory based on deductive logic such as the syllogism is categorically incapable of establishing the existence of its terms, whether in the premises or in the conclusion. Theory seeks to find the ordo et connexio rerum et idearum whereby symbols such as words and propositions are linked directly to things so as to offer, as it were, a “universal key” (clavis universalis) to the reading and interpretation of “the Great Book” of divine creation to which human beings are made privy. Not only is there no ordo et connexio rerum et idearum, not only is there no adaequatio rei et intellectus, but also any attempt to link objects to ideas and to the intellect in an “order” dictated by reason and logic must fail because reason and logic are categorically incapable of establishing – certainly not “logically”! – the real existence of the very “objects” that logic wishes to connect and that reason wishes to order! The only “quality” or attribute that may be inferred from our natural perception of “beings” is that which is common to all of them – Being.
Again, if a certain property can exist only in virtue of such and such a cause, from every such property that appears in the effect, we can infer the existence of the cause. Now it is not just such properties of the effect as are treated in the philosophy of nature that are possible CONCERNING METAPHYSICS 11 only on condition that God exists, for the same is true of the properties treated of in metaphysics. Not only does motion presuppose a mover, but a being that is posterior presupposes one that is prior. Consequently, from the priority that exists among beings the existence of the First Being can be inferred, and this can be done in a more perfect way than the existence of a Prime Mover can be established in natural philosophy. We can infer, then, in metaphysics from act and potency, finiteness and infinity, multitude and unity, and many other such metaphysical properties, that God or the First Being exists. So far as this article is concerned, then, I say that God is not the subject of metaphysics, because, as has been proved above in the first question, there is but one science that has God as its first subject [theology], and this is not metaphysics.10
Metaphysics, as the prima philosophia, deploys the human intellect for the understanding of Being as Substance. Yet once we acknowledge that God is not immediately apprehended by the human intellect because the latter relies on the senses to understand and fix its object of study, it becomes obvious then that God, as a suprasensible Being, is not and cannot be the subject of metaphysics.
 And so the concept of being, in so far as it agrees with the concept in question, is other than the dubious concepts which come under it. But it is other in such a way that it is included in both of the concepts which come under it, for these limiting differences presuppose the same concept of being which they limit. The second reason I explain as follows: We argued that God cannot be known naturally unless being is univocal to the created and uncreated. We can argue in the same way of substance and accident, for substance does not immediately move our intellect to know the substance itself, but only the sensible accident does so. From this it follows that we can have no quidditative concept of substance except such as could be abstracted from the concept of an accident. But the only quidditative concept of this kind that can be abstracted from that of an accident is the concept of being.
And yet, metaphysics can point to the existence of God, although it will never be able to comprehend the Deity because the divine is categorically different from the objects comprehensible by the human intellect. Metaphysics can do this not by analogy or by revelation, as St. Augustine and St. Thomas Aquinas would have it, but through the intellectual notion of “being”. Both analogy and revelation fail because the one is purely figurative whereas the second assumes – through divine intervention, that is, by wholly “irrational” means, through blind faith - what needs to be proven.
Of every subject, also of a subordinate science, it is known through the senses that it is of such a nature that to exist is not repugnant to it, as is evident of the subject of optics, for the existence of a visible line is grasped immediately from the senses. Just as principles are grasped immediately once the terms are apprehended through the medium of the senses, so likewise if a subject is not to be posterior to, or less known than, its principle,11 it must needs be grasped through the senses. But no proper notion that we can form of God is apprehended immediately by man's intellect in this life. Therefore, we can have no naturally acquired science about God under some notion proper to Himself. Proof of the minor: The first [proper] concept we have of God is that He is the First Being. This notion is not grasped through the senses, but we must first ascertain that the union of these two terms is compatible. Before we can know this compatibility, however, it is necessary that we demonstrate that some being is first. Therefore, etc. Hence, I concede with Avicenna that God is not the subject of metaphysics. (D. Scotus, PW, pp.10-11.)
Implicit in this categorization of the being and its accession to the Deity (the Uncreated) is the ascertainable superiority of metaphysics – and then of the natural sciences - as the purview of the intellect as against faith. Hereafter, the object of science is not the search of the causa ultima or causa causans but rather that of efficient causes and effects. If every cause must have an effect and vice versa, then the First Cause must be able to create, yet not itself be created – which means that it is toto genere different from all other events in the causal chain – and therefore, as such, not comprehensible by and to the human intellect except through the apprehension of being!
Une science est l'ensemble des vérités sur un sujet. L'idéal de la science, selon Duns Scot, serait d'avoir pour principe, par l'intuition complète de son objet, la défnition qui en exprime l'essence, et d'apercevoir les conséquences nécessaires d'un tel principe 4 . Mais il avoue que cet idéal n'est pas possible pour nous ; une distinction lui est familière entre la science en soi et la science par rapport à nous, et aux questions posées sur l'objet et la méthode de la science, les solutions qu'il donne diffèrent suivant ces deux points de vue succes -38-ifs. « Le propre de la métaphysique, dit-il ', est de fonder ses divisions et définitions sur l'essence, puis de faire des démonstrations par la considération des causes essentielles absolument premières... Mais c'est le propre de la métaphysique en soi. Ce n'est pas ainsi que nous en avons la science, ni qu'elle est enseignée par Aristote. Cherchez dans tout son livre : vous n'y trouverez pas une seule démonstration de métaphysique à priori, car, par suite de la faiblesse de notre intelligence, c'est en partant des choses sensibles et moins intelligibles en elles-mêmes que nous venons à la connaissance des choses immatérielles qui en soi sont plus intelligibles (notiora) et devraient être en métaphysique prises comme les principes de la connaissance des autres choses. » L'ange peut-être aurait pu, selon Duns Scot 2 , « de la connaissance naturelle de Dieu déduire toute autre connaissance; » mais ce n'est pas notre cas, et nous ne pouvons commencer la science en supposant l'existence de Dieu ni la fonder sur sa notion 3 : en effet, avant l'expérience des sens — 39 — il n'y a aucun principe qui nous soit naturellement connu, (E. Pluzanski, Essai sur la Philosophie de Duns Scot, pp.38-39).
Human beings, argues Scotus, cannot have a natural knowledge of God because the divinity is beyond the reach of our senses, of our perception, on which all of our natural knowledge, the sciences, must be founded. There are aspects of being that are merely qualitative or attributive or adjectival (in quale), whereas there is a more intrinsic quiddity or whatness (quidditas) of being (in quid) that cannot be qualified further. The proper subject of metaphysics, argues Scotus, is precisely the relationship of this quiddity to its qualities, that is, the relationship of being to its “mere appearances” (recall Kant’s distinction between thing-in-itself and mere appearances). We cannot start from the existence of God, of the Word as Logos, and then proceed to deduce analytically and syllogistically the essence of the natural sciences. It is rather the other way round! Starting with our experience, we can then project through our intellect the essential attributes of the Divinity, of Being.
This vital distinction between knowledge and faith – preferring the former even as a buttress to faith – is what marks Duns Scotus as the probable founder of modern Western philosophy and establishes its point of departure from Scholastic theology. The existence of God can be shown only in quid, only through transcendental logic, not in quale, that is, not through the logica practica. (For the distinction, see D. Scotus, Philosophical Writings, Notes to s,1.) But then, God cannot be said to exist in the way real beings exist because the Deity as Being does not exist in time like beings; “it creates but is not created” – and in that sense it is Being in quid (Sein) as distinct from being in quale (Seiende, etants, in French) that “is created and either creates or does not create”. Scotus’s complex Orationes came to the attention of Heidegger because of this subtle distinction between being in quid and being in quale, which is what opened his bush-path (Holzweg) to an anthropological perspective of being and existence based, emphatically, on the finitude of beings.