God can be named by us only from the analogy of creatures, not from what He is in Himself; but we name Him as He is known to us through creation by way of excellence, and by way of negation, that is, in an affirmative and negative sense. In this life we do not know the Essence of God as He is, and because we know Him as imperfectly represented by creatures, all such names are imperfect and are inadequate to express the Divine Substance. So when we say "God is good" the meaning is not, God is the Cause of good, or God is not bad; it means that what is called good in creatures pre-exists in God in a higher sense. For it does not follow that goodness is attributed to God because He is the Cause of goodness; rather, conversely, because He is Himself good He diffuses goodness in creatures, as Saint Augustine says: "Inasmuch as He is good, we are."
Some names are properly applied to God because of their meaning, and to Him first and more properly than to creatures, such as goodness, life, etc. These, indeed, are perfections existing in God in a more eminent manner than in creatures, but in respect of their mode of signification they cannot be, strictly speaking, applied to God, because such a mode is on a level with creatures, and such perfections are understood by us as they exist in creatures, and are named by us as they are thus understood. Although the names attributed to God signify one, still they signify it in a multiform and diverse aspect, and are, therefore, not synonymous; for perfections exist united and absolutely in God, whereas creatures can receive them only in a divided and multiform manner.
Nor are those terms which are applied to God and creatures used in the same sense, and the reason is because an effect which does not equal the force of the cause is a recipient of that, divided and manifold, which in the cause is simple and uniform. Thus in a man to be wise means something distinct from the essence of man. But neither are they used equivocally (i. e. in a wholly different sense) of God and creatures, for were that so, nothing could be known or inferred from creatures about God, contrary to that shown above; it is, therefore, by way of analogy, i.e. proportion, that the same terms are applied to God and to creatures, for there is a certain orderly relation of the creature to God, as He is the Principle and Cause in Whom pre-exist excellently all created perfections. This way stands between the two, pure equivocation and simple univocation; forasmuch as in analogy there is not one idea only, as in the univocal order, nor that entire difference which marks the equivocal order, since there is signified in it diversity of proportion in relation to the unit.
Names which are applied metaphorically to God are derived from creatures, and not from God, forasmuch as when they are spoken of God they only signify His likeness to certain creatures, as when we apply to God the name of "Lion" we signify that the strength of God shown in His works is like the lion's strength in its sphere of action; while, on the contrary, what is signified by the name belongs first to God rather than to the creature, for perfections flow from God to creatures. When we consider the imposition of the name, however, we give it first to those we know first, to creatures.
Names also implying temporal relations to creatures are assigned to God, for although He is outside the order of the universe, all creatures being ordered to Him as their End, and not, conversely, He to them, they bear a relation to Him, while God has no relation to creatures, except as a notion, for God and creatures are not of the same order. Thus the names of "Lord," "Redeemer," and others like them, implying temporal relations, may be given to God.
The very name of "God" belongs to the Divine Nature as regards that to which it is given, but as regards that from which it is taken, it expresses effect or operation, being derived from the idea of universal Providence, for when we speak of God by this name we mean to express that He takes care of all. And as this name is used to signify the Divine Nature, which is not multiple, it cannot be communicated in reality, except only in the .opinion of those who assert there are many gods; yet still it is communicable, not in its full meaning, but according to some kind of likeness, as those are called gods who participate in the Divine Likeness, while if it were a name that signified not the Nature but the Personality of God, such a name would be wholly incommunicable. And this name of "God" is not applied to God univocally nor equivocally, that is in quite the same or quite a different sense, but analogically, by participation, and according to nature and notion: for when we name God by participation, we mean by the name "God" anything that has the likeness of the true God; and when we call an idol god, we mean something that men think is God: thus the meaning of the name has various aspects, though one is contained in the rest, from which we infer that it^ is used analogically. The name "He is" or "I am" is most strictly applicable to God, for it signifies not form but His very Existence, and in God alone is His Essence His own very Existence, and everything else is denominated by its form; whilst it is evident that the Essence of God cannot be understood by us in this life as it is in itself, and hence everything that is understood in any explicit way falls short of God as He is in Himself. Hence the more extended and less determined names are the more suitably applied to Him Who is the Infinite ocean of substance and indetermined. Moreover, it is plain that because existence signifies the present, it is most properly said of God, Who knows neither past nor future. And further, because God in Himself is One and Simple, and we cannot see Him as He is, we understand Him according to different conceptions, for we cannot see Him as He is, but we understand Him in various ways that correspond, as we know, to one and the same. Hence the notional plurality in our minds represents the predicate and subject in that guise; nevertheless, unity is realized in the mind of composition.
- text taken from Compendium of the Summa Theologica of Saint Thomas Aquinas, by Bishop Berardus Bongiovanni