According To The Teaching of St. Thomas Aquinas
II
According to Plato's teachings, and they coincide on this point with the teachings of Faith, every created being is a participation in the Divine being, and every created perfection is in some manner a participation in infinite perfection. Thus our nature is a participation in the Divine perfection; 2 the light of our intelligence is a participation in the uncreated intelligence; our life, a participation in the life of God. Briefly, every particle of goodness, of perfection, of being in any creature whatsoever, is a participation in the being and goodness of God. 3
We must not conceive this communication of God to His creatures as a division of the Divine essence, just as one divides and distributes the parts of a fruit; rather, the Divine essence preserves its unity and fullness. Nor should we regard it as an emanation properly so-called, or a flowing out, an effusion of the Divine substance as rivulets flow from a single source, or as a warm body sheds its rays and heat upon everything that is near. The Divine goodness externizes itself by producing beings like unto itself, yet without any diminution of the Divine substance; 4 for only its likeness is imparted to creatures. The process is akin to the impression of the seal on the wax, without any communication of the former's substance to the latter.
Hence this participation of creatures in the Divine goodness is not any community of being and perfection. Such a doctrine is pantheistic. Creatures have their own being, and their own goodness, which is at once the intrinsic and the formal cause, making them what they are. They are related to God inasmuch as God is their extrinsic cause, and this in a threefold sense, namely, the ideal according to which they have been created; the efficient cause; and the final and ultimate cause of their creation. 5
Not without reason then did the Fathers, and, under their influence, St. Thomas, speak of creatures as beings by participation, entia per participationem, and of their perfections as participated perfections. In so speaking they had a twofold purpose; first, clearly to establish the profound difference between the Creator and*creature, or rather the abyss which separates them; second, to impress upon men the fact, that every created being essentially depends on God as upon its exemplar and its efficient cause of existence. Indeed, the very words, participated being, signify a being that is finite, limited, restricted; for participation in anything, a family heritage, for example, means to take a part and not have entire possession. The same words further imply a borrowed being, a contingent being, a being proceeding from another being, and essentially depending upon some extrinsic cause. From the very fact that a thing is not being itself in all its plenitude—the ocean of being—but a mere rivulet or stream, it follows that what it possesses of being is not its own in virtue even of its essence, but comes to it from without, just as every tiny stream supposes a generating spring or fountain.
In speaking of creatures, then, as entities participating of the deity, we wish to assert two tryths: first, creatures do not possess being in all its fullness, but have merely a part of it, varying among themselves in quantity if you will, but essentially limited and restricted; secondly, this limited and restricted being does not accrue to them in any essential manner, even in virtue of their nature, but has been communicated to them by an extrinsic cause—God. In much the same way to the glowing steel has been imparted warmth and brilliancy by the operation of an outside agency, not because its nature demands it, but because it is igneous only by participation.
The Divine being, on the contrary, is not a borrowed being, a being proceeding from another. God holds His being from no one, for He has it by virtue of His nature. "He is, then, self-existent being Ens per se, being by essence, in opposition to being that is contingent and dependent on another— He is also preeminent being, self-subsistent,and consequently He is infinite being, the very plenitude of being,. And if He is being in all its fullness, nothing can exist beyond Him, which is not traceable to Him as to its source, and which is not present in Him in a super-eminent manner. Thus whatever being is outside of Him cannot be called simply being, rather they are beings —that is to say, participation's in and imitations of being."
1 St. Thomas, Summa Theologica, I., q. xliii., a. 3.
2 Ibid., Summa Theologica, I., q. xiv., a. 6.
3 Ibid., Summa Theologica, I., q. xii., a. 11, ad. 3; and I., q. vi., a. 4.
4 St. Thomas, Comment in lib. de divinis Nom., c. ii., lect. 6.
5 Ibid., Summa Theologica, I., q. vi., a. 4.
6 St. Thomas, Contra Gent., l, n., c. xv.