Objection 1. It seems that no name is applied literally to God. For all names which we apply to God are taken from creatures; as was explained above (Article 1). But the names of creatures are applied to God metaphorically, as when we say, God is a stone, or a lion, or the like. Therefore names are applied to God in a metaphorical sense.
Objection 2. Further, no name can be applied literally to anything if it should be withheld from it rather than given to it. But all such names as "good," "wise," and the like are more truly withheld from God than given to Him; as appears from Dionysius says (Coel. Hier. ii). Therefore none of these names belong to God in their literal sense.
Objection 3. Further, corporeal names are applied to God in a metaphorical sense only; since He is incorporeal. But all such names imply some kind of corporeal condition; for their meaning is bound up with time and composition and like corporeal conditions. Therefore all these names are applied to God in a metaphorical sense.
On the contrary, Ambrose says (De Fide ii), "Some names there are which express evidently the property of the divinity, and some which express the clear truth of the divine majesty, but others there are which are applied to God metaphorically by way of similitude." Therefore not all names are applied to God in a metaphorical sense, but there are some which are said of Him in their literal sense.
I answer that, According to the preceding article, our knowledge of God is derived from the perfections which flow from Him to creatures, which perfections are in God in a more eminent way than in creatures. Now our intellect apprehends them as they are in creatures, and as it apprehends them it signifies them by names. Therefore as to the names applied to God--viz. the perfections which they signify, such as goodness, life and the like, and their mode of signification. As regards what is signified by these names, they belong properly to God, and more properly than they belong to creatures, and are applied primarily to Him. But as regards their mode of signification, they do not properly and strictly apply to God; for their mode of signification applies to creatures.
Reply to Objection 1. There are some names which signify these perfections flowing from God to creatures in such a way that the imperfect way in which creatures receive the divine perfection is part of the very signification of the name itself as "stone" signifies a material being, and names of this kind can be applied to God only in a metaphorical sense. Other names, however, express these perfections absolutely, without any such mode of participation being part of their signification as the words "being," "good," "living," and the like, and such names can be literally applied to God.
Reply to Objection 2. Such names as these, as Dionysius shows, are denied of God for the reason that what the name signifies does not belong to Him in the ordinary sense of its signification, but in a more eminent way. Hence Dionysius says also that God is above all substance and all life.
Reply to Objection 3. These names which are applied to God literally imply corporeal conditions not in the thing signified, but as regards their mode of signification; whereas those which are applied to God metaphorically imply and mean a corporeal condition in the thing signified.
Source: Summa Theologica (New Advent)