Pieper was a 20th-century German Thomist whose work has been discussed on this site before, and who always deserves more attention. What made Pieper stand out from many of his fellow Thomists was that while he always maintained a realist outlook, he placed great emphasis on the limits of knowledge. For instance, in The Silence of St. Thomas, Pieper demonstrated how Aquinas incorporated the via negativa of Pseudo-Dionysius into the core of his own work. Pieper always placed in the foreground of his writing the paradox that things are intelligible in themselves because they have been created by God, but are not comprehensible by our intellect because God's intellect surpasses ours by so much. Here is a quotation from part VI of "A Plea for Philosophy" that explains this paradox:
The sentence "omne ens est verum" [everything that is is true]. . .has two aspects. The one enables us to recognize an ever deepening access to all existing things; the other, the impossibility of ever reaching rock bottom. Both aspects. . .are empirically verifiable facts. That, however, both may be traced back to the same origin; that they are even in a certain sense identical; that, more specifically, the things are, taken for themselves, knowable in their ultimate constitution because they originate in the infinite brightness of the divine logos and that they are at the same time unfathomable to us precisely because they originate in the infinite brightness of the divine logos--this is not empirically verifiable.This paradox leads Pieper to the conclusion that, in the face of our inability to comprehend the meaning of the cosmos, agnosticism is not enough. This paradox should instead lead us to wonder, awe, and a "sense for mystery":
Now, what is meant here by mystery is not something exclusively negative and more than simply what is obscure. In fact, when understood more precisely, mystery does not imply obscurity at all. It connotes light, but a light of such plenitude that it remains "unquenchable" for a knowing faculty or a linguistic capacity that is merely human. The notion of mystery should not suggest that the effort involved in thinking runs up against a wall but rather that this effort exhausts itself in the unforeseeable, in the space--the unlimited breadth and depth--of creation.We never will find all the right answers to the big questions. Nevertheless, that should not prevent us from setting out on the journey.