In Question 13, article 5 of his Summa Theologica, Aquinas identifies three forms of predication (or 3 ways to use words to predicate things of God). The first is univocal—using a term in exactly the same way of more that one subject (this desk and that desk are both “desk”; no need to change the term). The second is pure equivocal—this is to use the same word, but the subjects are different (e.g., pointing to a picture of someone and then to the actual person and calling each “Bob”; there’s something in common, but the two are obviously different). Third is analogical—this is what Aquinas uses between creatures and God.
[Analogous language] can happen in two ways: either according as many things are proportioned to one (thus, for example healthy is predicated of medicine and urine in relation and in proportion to health of body, or which the latter is the sign and the former the cause), or according as one thing is proportioned to another (thus, healthy is said of medicine and an animal, since medicine is the cause of health in the animal body). And in this way some things are said of God and creatures analogically, and not in a purely equivocal nor in a purely univocal sense.
As we see Aquinas uses the word “healthy” to make things clearer. Similarly, both God and the tree receive the name “being” analogically. Hence, God and the tree are called “being,” not in two totally different senses—for there is some similarity, some analogy, though not in the same (univocal) sense, either. Just as both the body and the food are “healthy,” so both God and creature are “being.”
Incidentally, this raises an interesting question: if one knows nothing of God, how much can one learn of God’s being, simply by examining the tree? Aquinas says they have some relation, true; but if we only know one term of that relation (the tree), how much can it really tell us of the other (God)? Simply put, functionally speaking, how different is analogical predication from equivocal predication?
We are led, then, back to Question 13, article 2, respondeo, of the ST: how are our names for God applied to Him? Aquinas begins his response by identifying three different kinds of names for God. “Names which are said of God negatively [that’s one] or which signify His relation to creatures manifestly [that’s two] do not at all signify His substance, but rather express the distance of the creature from Him, or His relation to something else, or rather, the relation of creatures to Himself. But as regards names of God said absolutely and affirmatively [that’s three], as good, wise, and the like, various and many opinions have been held.” So, we have (1) negative names, (2) names that signify a relation to creatures, and (3) absolute, affirmative names. Concerning absolute, affirmative names, Aquinas treats three different opinions: that of Maimonides and that of some others—but, due to his rejections of these first two, it is the third which Aquinas favors. He believes the only thing absolute, affirmative names signify is the divine substance and are predicated substantially of God, though they fall short of representing Him. So, absolute, affirmative names which do not simply signify a relation to creatures and are not negative, signify the substance of God (this is how we get material for sacra doctrina). One qualification, however: when we predicate “life” or “being” of God, we do so “in an imperfect manner, even as creatures represent it imperfectly.” Hence, our names do signify the divine substance, but we do not have knowledge of the substance of God—they do not impart knowledge of the divine substance.
John Duns Scotus also had a theory of predication regarding God. For Scotus, our knowledge of God is univocal, which he begins describing in Book I, Distinction III of his Commentary on the Four Books of Peter Lombard. He begins by saying, “there should be no distinction made as to whether God can be known negatively rather than affirmatively, since negation is only known through affirmation…. It is also obvious that we only understand negations concerning God by way of affirmations, as, for instance, we do not remove compositeness unless we attribute simplicity or some such” (Ordinatio I, d. 3). So it’s fine, he says to his predecessors (one thinks especially of Dionysius), to use negative language to talk about God, but you must understand that this is not somehow higher than affirmation, rather negation depends upon affirmation. He continues, “If a negation, such as not-stone, is conceived in isolation, this pertains as much to nothing as it does to God. Thus God is no more understood in this than is nothing, or the chimaera” (p. 603). But this, of course, is not how we want to talk about God. Thus, we do not want to take negations in isolation. If we want negations to say more about God than they do about nothing, then they must be related to an affirmation on which they are dependent. Thus, our names serve to say something positive about God. So, one can’t say in isolation that God is non-being (as Dionysius would). Rather, one must say that God is non-being in the sense that creatures are being.
Moreover, “it can be said that God is conceived not only in a concept by analogy with the concept of a creature…but in some concept univocal to Himself and a creature” (p. 603). This means “a concept whose unity suffices for contradiction when it is affirmed and denied of the same thing” (p. 604). This turn toward speaking of both God and creatures as “being(s)” in the same (univocal) way is often regarded as a shift toward Modernity. Scotus claims one can confidently call God “being,” while at the same time doubting whether it is finite or infinite being—and this is the same being had by creatures. God’s being may be very different from that of creatures when we add on what kind of being it is, but when we simply use the term “being” of God and creatures, we can do so univocally. It may be argued that Aquinas is doing something similar: we know that God exists, that He has being. We don’t know what (or what kind) that being is. This, Scotus notes, just is univocal language: when we say that God exists, we’re using “being” univocally between God and creatures. When we say we don’t know what kind of being it is, fine, there’s something we don’t know about God’s being. But when we simply say “being,” we’re using that concept univocally. Hence, to the extent that we simply use the term “being,” we do so univocally.
This may be found in Philosophy in the Middle Ages: the Christian, Islamic, and Jewish Traditions 2d ed., ed. Arthur Hyman and James Walsh (Indianapolis: Hackett, 1983), p. 602. Subsequent page references are to this edition.