The Doctrine of the Trinity, hitherto explained and abundantly confirmed, our AUTHOR now at length commends from its Sublimity, § 28; from its Necessity, § 29, and also from its Utility, § 30.
The Doctrine of the Trinity is so sublime, that it surpasses the Reason of corrupt Man, from which it is not able to be proven. For, that the situation was otherwise with Man in his Integrity, was seen in Chapter I, § 16. But, since of that Wisdom, which with the divine Image was granted to Adam by Creation, only certain rougher fragments, regarding whatever acquaintance with God as τοῦ γνωστοῦ, survive after the Fall; see Chapter I, § 18-20: we are not able to return to that more thorough knowledge of God and this Mystery without the light of Revelation. But, although this doctrine surpasses the Reason of Corrupt Man, it is not opposed to Right Reason in the abstract: compare above, Chapter I, § 32, Chapter V, § 20.
That Sublimity of the doctrine of the Trinity just now declared, our AUTHOR proves, both, α. from the many and quite express Passages of Scripture, indicating the Mystery in the knowledge of this doctrine, not to be learned except out of Supernatural Revelation; and, β. from the Experience of every age, since many men, externally illuminated, have continually opposed it; and, γ. from the Imbecility of the Reasons adduced for the confirmation of this doctrine, and the Dissimilarity of the Similitudes, when you will have called the same in for examination.
The Scholastics depart unto the contrary opinion, and some of Our Men follow these. Thus MORNÆUS, de Veritate Christianæ Religionis, chapter V: he does indeed acknowledge that this Mystery has never been known by the acumen of Reason; nevertheless, after the Revelation of the same by God, that same Reason, says he, that never discovered that doctrine, sees, considers, and approves it, even if nothing approached or was added to the Reckoning of Reason from that Revelation: which he illustrates by the similitude of an eye seeing many things clearly after the light of the Sun has dawned, while previously the Sun and the things under the Sun were not discerned without the Sun. POIRET, Cogitationibus Rationalibus, book III, chapter I, pages 227-229, takes upon himself to prove this Proposition: From the consideration of the nature of God alone, viewed without regard to creatures, it is evident that there is in that something Holy and inviolable, TRINITY. JACOB ALTING, Dissertation V Heptadis Sextæ, Dissertationibus Academicis, opera, tome 5, pages 175-179, attempts to prove, that the knowledge of the Trinity also perstains to the Knowledge concerning God Innate in every man even after the fall. JOHANN CLAUBERG,Disputationibus XII, openly undertakes to demonstrate the Trinity from natural reasons: and NICOLAUS SMITERUS, Professor of Philosophy at Duisburg, in his Meditatione de Trinitate, expressly denies that the doctrine of the Trinity is a Mystery, and by completely evident demonstrations (as he calls them), clearly and distinctly perceived by him, attempts to render it manifest, that the Trinity is able to be known without Revelation: VAN MASTRICHT, Gangræna Novitatum Cartesianarum, posterior Section, chapter XVII, pages 310-325, takes upon himself to refute and turn back the idle chatter and reasons, inept and unworthy of God, of this Smiterus especially. Meanwhile, already of old AUGUSTINE, libris XV de Trinitate, especially from book VI to book XV, and also The City of God, book XI, sought the Image of the Trinity in almost all created things. Although MARESIUS, Systemate Theologico, locus III, § 42, supposes that the arguments advanced from the discourse of Reason alone on behalf of the Trinity are not able to convince; he nevertheless thinks that, with Revelation supposed, this Mystery is able in some measure to be illustrated, both by certain probable arguments and by similitudes not altogether unsuitable: and he reckons it to be of excessive confidence and αὐθαδείας/presumption, that AMYRAUT employed all the acumen of his genius, in his Dissertationibus de Trinitate published at Saumur, to overthrow whatever the founder and protector of that Illustrious Academy had set forth upon this matter against the Atheists; in this only refraining from him, that he did not name him. BARTHOLOMAUS KECKERMANN discourses in a similar manner; see BECMANN, Exercitationibus Theologicis, XI, pages 149-151, where many others are cited in addition, who made ue of similar argumentation for the Trinity. For a sober and legitimate use of Similitudes, whereby the doctrine of the Trinity is explained by the Father, see ZANCHI, de Tribus Elohim, former part, book VIII, chapter VI, opera, tome I, columns 356-358.
 Philippe de Mornay (1549-1623), a Frenchman, was a politically active apologist for Protestantism.  Johann Clauberg (1622-1665) was a German Reformed theologian, and proponent of Cartesian philosophy. He served as Professor of Philosophy and Theology at Herborn (1649-1651), and Professor of Theology at Duisburb (1652-1665).  Namely, Philippe de Mornay.