I’ve been working my way through Aquinas’s late, brief summary of his system, Compendium Theologiae, and it’s been a dense, instructive dive so far.
Early in his series of questions on creation, he treats the matter of why there is plurality, or a diversity of things in creation. Why are there trees and monkeys and mountains and starfish, instead of only, say perfectly spiritual beings like angels? Why stars of various shapes, colors, and sizes, instead of one, perfect, massive orb? Why diversity instead of simple, orderly, uniformity?
Well, as with most things in Aquinas, he finds the answer in God who is their creating and sustaining cause. Even more than that, he roots this diversity in the simplicity of God.
Any active cause must produce its like, so far as this is possible. The things produced by God could not be endowed with a likeness of the divine goodness in the simplicity in which that goodness is found in God. Hence what is one and simple in God had to be represented in the produced things in a variety of dissimilar ways. There had to be diversity in the things produced by God, in order that the divine perfection might in some fashion be imitated in the variety found in things.
Furthermore, whatever is caused is finite, since only God’s essence is infinite, as was demonstrated above. The finite is rendered more perfect by the addition of other elements. Hence it was better to have diversity in created things, and thus to have good objects in greater number, than to have but a single kind of beings produced by God. For the best cause appropriately produces the best effects. Therefore it was fitting for God to produce variety in things. (1:72)
One might think that the indivisible, simple being of God would stifle diversity. Thomas reminds us, though, that the simple being of God is infinite. A mere repetition of the same finite effects will not do. In order to begin to communicate the fullness of his refulgent glory by way of finite creaturely reality will require a diversity of finite causes!
Despite it’s philosophical garb, I think this really functions as a metaphysical gloss on Scriptural teaching. Consider what the Psalmist tells us:
The heavens declare the glory of God;
the skies proclaim the work of his hands.
Day after day they pour forth speech;
night after night they reveal knowledge.
They have no speech, they use no words;
no sound is heard from them.
Yet their voice[b] goes out into all the earth,
their words to the ends of the world. (Ps. 19:1-4)
How many are your works, LORD! In wisdom you made them all;
the earth is full of your creatures.
There is the sea, vast and spacious, teeming with creatures beyond number— living things both large and small. (Ps. 104:24-25)
Thomas tells us that all this marvelous diversity is a reflection, a testimony to the wisdom, glory. and beauty of the simple God. In the creation of diverse effects, it is as if the pure, undivided brightness of the infinite divine light is refracted before our eyes as through a prism as broad and as wide as the universe itself.
Soli Deo Gloria