Summa contra Gentiles1.31 Chapter XXXI. That the divine perfection and the plurality of divine names are not inconsistent with the divine simplicity

From what has been said we are also able to see that the divine perfection and the various names applied to God are not inconsistent with His simplicity.

For we asserted that all the perfections to be found in other things are to be ascribed to God in the same way as effects are found in their equivocal causes: which causes are in their effects virtually, as heat is in the sun. Now this virtue unless it were in some way of the genus of heat, the sun acting thereby would not generate its like. Wherefore by reason of this virtue the sun is said to be hot, not only because it causes heat, but because the virtue whereby it does this, is something in conformity with heat. Now by this same virtue by which the sun causes heat, it causes also many other effects in lower bodies, such as dryness. And so heat and dryness, which are distinct qualities in fire, are ascribed to the sun in respect of the one virtue. And so too, the perfections of all things, which are becoming to other things in respect of various forms, must needs be ascribed to God in respect of His one virtue. And this 1 Ch. xiv. 2 Ch. xxix virtue is not distinct from His essence, since nothing can be accidental to Him, as we have proved. 'Accordingly God is said to be wise not only because He causes wisdom, but because in so far as we are wise, we imitate somewhat the virtue whereby He makes us wise. He is not however called a stone, although He made the stones, because by the term stone we understand a definite mode of being, in respect of which a stone differs from God. But a stone imitates God as its cause, in respect of being, goodness and so forth, even as other creatures do.

The like of this may be found in human cognitive powers and operative virtues. For the intellect by its one virtue knows all that the sensitive faculty apprehends by various powers, and many other things besides. Again, the intellect, the higher it is, the more things is it able to know by means of one, while an inferior intellect can arrive at the knowledge of those things only by means of many. Again the royal power extends to all those things to which the various subordinate powers are directed. And so too, God by His one simple being possesses all manner of perfections, which in a much lower degree other things attain by certain various means. Whence it is clear how it is necessary to give several names to God. For since we cannot know Him naturally except by reaching Him from His effects, it follows that the terms by which we denote His perfection must be diverse, as also are the perfections which we find in things. If however we were able to understand His very essence as it is, and to give Him a proper name, we should express Him by one name only: and this is promised in the last chapter of Zacharias to those who will see Him in His essence: In that day there shall be one Lord, and His name shall be one.