Ch. 24 "God's Simplicity Not Contradicted by the Multiplicity of Names Applied to Him" From the "Compendium of Theology" by St. Thomas Aquinas

CHAPTER 24 GOD’S SIMPLICITY NOT CONTRADICTED BY THE MULTIPLICITY OF NAMES APPLIED TO HIM

Per hoc autem apparet ratio multitudinis nominum quae de Deo dicuntur, licet ipse in se sit omnimode simplex. Cum enim intellectus noster essentiam eius in se ipsa capere non sufficiat, in eius cognitionem consurgit ex rebus quae apud nos sunt, in quibus inveniuntur diversae perfectiones, quarum omnium radix et origo in Deo una est, ut ostensum est. Et quia non possumus aliquid nominare nisi secundum quod intelligimus (sunt enim nomina intellectuum signa), Deum non possumus nominare nisi ex perfectionibus in aliis rebus inventis, quarum origo in ipso est: et quia hae in rebus istis multiplices sunt, oportet multa nomina Deo imponere. Si autem essentiam eius in se ipsa videremus, non requireretur nominum multitudo, sed esset simplex notitia eius, sicut est simplex essentia eius: et hoc in die gloriae nostrae expectamus, secundum illud Zachar. ultimo: in illa die erit dominus unus, et nomen eius unum.

This enables us to perceive the reason for the many names that are applied to God, even though in Himself He is absolutely simple. Since our intellect is unable to grasp His essence as it is in itself, we rise to a knowledge of that essence from the things that surround us. Various perfections are discerned in these things, the root and origin of them all being one in God, as has been shown. Since we cannot name an object except as we understand it (for names are signs of things understood), we cannot give names to God except in terms of perfections perceived in other things that have their origin in Him. And since these perfections are multiple in such things, we must assign many names to God. If we saw His essence as it is in itself, a multiplicity of names would not be required; our idea of it would be simple, just as His essence is simple. This vision we hope for in the day of our glory; for, according to Zacharias 14:9, “In that day there shall be one Lord, and His name shall be one.”