“In the philosophy of St. Thomas Aquinas, there is a fundamental idea by which almost all the basic concepts of his vision of the world are determined: the idea of creation, or more precisely, the notion that nothing exists which is not creatura, except the Creator Himself; and in addition, that this createdness determines entirely and all-pervasively the inner structure of the creature.
“As regards the ‘Aristotelianism’ of St. Thomas Aquinas (‘Aristotelianism’ is a highly dubious term, to be applied with caution), we shall completely miss the significance of his turning to Aristotle, unless we consider it from the point of view of this fundamental idea, worked out to its logical consequences: namely, that all things are creatura, not merely soul and spirit, but also the visible world.
“It may appear natural enough, scarcely worth discussion, and in any case not at all surprising, that the conceptual thinking of a theologian of the Middle Ages should be dominated by the notion of creation, even in his philosophical explanation of reality. What might cause wonder is the extent to which it is here a question of an unexpressed assumption, an opinion not explicitly formulated, that has, as it were, to be read between the lines. Did not Thomas develop fully and explicitly a doctrine of creation? That naturally is true and quite well known. None the less, it is equally true, though not so well known, that the notion of creation determines and characterizes the interior structure of nearly all the basic concepts in St. Thomas’s doctrine of Being.”
-Josef Pieper, The Silence of St. Thomas