Carefully read all of the Angelic Doctor’s words on the subject of the names of God before going on:
as regards absolute and affirmative names of God, as “good,” “wise,” and the like, various and many opinions have been given. For some have said that all such names, although they are applied to God affirmatively, nevertheless have been brought into use more to express some remotion from God, rather than to express anything that exists positively in Him. Hence they assert that when we say that God lives, we mean that God is not like an inanimate thing; and the same in like manner applies to other names; and this was taught by Rabbi Moses. Others say that these names applied to God signify His relationship towards creatures: thus in the words, “God is good,” we mean, God is the cause of goodness in things; and the same rule applies to other names.
Both of these opinions, however, seem to be untrue for three reasons.
First because in neither of them can a reason be assigned why some names more than others are applied to God. For He is assuredly the cause of bodies in the same way as He is the cause of good things; therefore if the words “God is good,” signified no more than, “God is the cause of good things,” it might in like manner be said that God is a body, inasmuch as He is the cause of bodies. So also to say that He is a body implies that He is not a mere potentiality, as is primary matter.
Secondly, because it would follow that all names applied to God would be said of Him by way of being taken in a secondary sense, as healthy is secondarily said of medicine, forasmuch as it signifies only the cause of the health in the animal which primarily is called healthy.
Thirdly, because this is against the intention of those who speak of God. For in saying that God lives, they assuredly mean more than to say the He is the cause of our life, or that He differs from inanimate bodies.
Therefore we must hold a different doctrine–viz. that these names signify the divine substance, and are predicated substantially of God, although they fall short of a full representation of Him. Which is proved thus. For these names express God, so far as our intellects know Him. Now since our intellect knows God from creatures, it knows Him as far as creatures represent Him. Now it is shown above (I:4:2) that God prepossesses in Himself all the perfections of creatures, being Himself simply and universally perfect. Hence every creature represents Him, and is like Him so far as it possesses some perfection; yet it represents Him not as something of the same species or genus, but as the excelling principle of whose form the effects fall short, although they derive some kind of likeness thereto, even as the forms of inferior bodies represent the power of the sun. This was explained above (I:4:3), in treating of the divine perfection. Therefore the aforesaid names signify the divine substance, but in an imperfect manner, even as creatures represent it imperfectly. So when we say, “God is good,” the meaning is not, “God is the cause of goodness,” or “God is not evil”; but the meaning is, “Whatever good we attribute to creatures, pre-exists in God,” and in a more excellent and higher way. Hence it does not follow that God is good, because He causes goodness; but rather, on the contrary, He causes goodness in things because He is good; according to what Augustine says (De Doctr. Christ. i, 32), “Because He is good, we are.”
(source: SUMMA THEOLOGIAE: The names of God (Prima Pars, Q. 13), emphasis added)