Lesson 11: The Analogy of Being
There are two crucial places in metaphysics where the notion of analogy comes into play. We will discuss these in turn, clarifying what is meant by analogy as we do so.
The Subject of Metaphysics
Let us recall the difficulties that confronted Aristotle when he asserted that, beyond the special sciences, each of which studies a particular kind of being, there is a further science which studies being as being. The primary obstacle to this assertion is the fact that "being" seems simply too unwieldy, vague and wide-ranging to provide a sufficient focus for a science. Aristotle agreed, in the sense that he insists that the problem is overcome by the fact of the primacy of substance. Being in the primary sense is substance so a science of being can effectively become a science of substance.
While this is familiar enough to you by now, I want to revisit it by calling attention now to the way in which Aristotle and Thomas establish this result. Aristotle concedes -- indeed insists -- that "being is said in many ways," that is, it is a term that has a plurality of meanings. As opposed to what? When I predicate "man" of Socrates, Xanthippe and Galileo, I would understand the same thing in each assertion. The common term would have exactly the same meaning in each use. Terms so shared are called univocal terms. We can sum this up in a definition. "Things are said to be named univocally which have both the name and the definition answering to the name in common." This is a quotation from the first chapter of Aristotle's Categories. But he has begun the discussion with another definition. "Things are said to be named equivocally when, though they have a common name, the definition corresponding with the name differs for each."
If I should say that there is a lock on my door, a lock on your forehead and a lock in the river, the common term "lock" exhibits Aristotle's definition of things named equivocally. The same would be true if I should say that when the boy stood on the burning deck he cut the deck or if I should speak of the key in my lock and one off the coast of Florida. Almost any dictionary entry of an English monosyllable will turn up such possibilities. There is nothing to be alarmed about in this, needless to say. To know the language is to know about the behavior of such words. It is true, however, that in an argument, recurring words have to bear the same meaning on penalty of committing the fallacy of equivocation. If I should speak of well-oiled locks you have to be on the qui vive lest I seek to conflate a security feature of doors and the golden hair that lies upon my lady's shoulder. Puns and verbal jokes depend upon such equivocation and we respond to them because we are both surprised and understand what is being done.
The fallacy of equivocation -- using a term in an argument with a number of meanings -- sums up the problem Aristotle faced. If "being" like "lock" and "key" have meany meanings, it would look as if he has to choose one of them and stick with it, and then he won't be talking about being as being, but about being of the kind meant by a single meaning of the term.
The way out of these particular woods is suggested by thinking of the way in which "healthy" and "medical" are sometimes used. While we can easily imagine uses which would lead us to say that they are functioning univocally and others where they are functioning equivocally, there are uses such that we would hesitate to say either. If I say that Fido and Pluto and Bowser are healthy, and "healthy" gets the same meaning in each use, it is functioning univocally. But what about this list:
 Bowser is healthy.
 Gravy Train is healthy.
 A sleek coat is healthy.
All these sentences are true, but this is not the case because "healthy" means the same thing in each use. On the other hand, it would be odd to say that there is no more similarity between the meanings we might assign it and those we would assign "lock" and "key" in our earlier examples. We seem to have uses which exemplify neither univocal naming nor equivocal naming. This is what Aristotle refers to as "things said in many ways but with reference to something one." Sometimes he speaks of on-purpose equivocals. His suggestion is that the analysis of such common terms will provide us with a way of handling the difficulties we face when we want to have a science of being as being. Thomas Aquinas calls names which behave in the way "healthy" does in the above list analogous names.
Such names are different from univocal and equivocal names -- indeed, they can be thought of as midway between them. They will be like equivocal terms in having a variety of meanings and they will be like univocal terms because this plurality is not destructive of unity. While there are indeed many meanings of an analogous term, those meanings are partly the same and partly different.
Thomas spells this out in the case of "healthy" by first noting that "healthy" is a concrete term which could be unpacked as: "that which has health." On this basis we can think of a kind of function of health Hx or a form like "__________ health" such that the several meanings of "healthy" represent different values of the variable x or different ways of filling in the blank. We could then restate our list as follows:
[1a] Bowser is the subject of health.
[2a] Gravy Train is preservative of health.
[3a] A sleek coat is indicative of health.
While the term "healthy" has this plurality of meanings as so used, they all involve health but differ in referring to it in a variety of ways.
Call that the first condition of a name's being used analogously. The second condition is this: one of those meanings is regulative or controlling of the others. That is, the many meanings of the common term form an ordered set, with one meaning primary and the others secondary. The meaning in [1a] is primary, something that can be seen by noting that while it is presupposed by other others, the verse is not true. When we say that a dog food is preservative of health, we may be taken to be saying sotto voce "preservative of health in the subject of health" and so too with [3a]. A sleek coat is indicative of health in the subject of health. Thomas will call this primary meaning the primary analogate of the shared term.
While "healthy" is the favorite example of both Aristotle and Thomas in this matter, it is of course the example of something that can be stated independently of it. Thomas proposes a second-order or logical language which captures what is true of "healthy" and states what is found in any analogous name.
"That which has health" = the ratio nominis, the meaning of the term. It is a second order term because it relates the meaning to a name, and that of course is not part of the meaning of the name.
"Health" = the res significata, the reality signified, the denominating form.
The blank or function of health = the modus significandi, the manner of signifying the denominating form.
With this terminology in hand, Thomas offers the following definitions:
...quando aliquid praedicatur univoce de multis, illud in quolibet eorum secundum propriam rationem invenitur, sicut animal in qualibet specie animalis. Sed quando aliquid dicitur analogice de multis, illud invenitur secundum propriam rationem in uno eorum tantum, a quo alia denominantur. Sicut sanum...
Summa theologiae, I, 16.6.
...something is predicated univocally of many things it is found in each of them according to its proper notion, as 'animal' is found in every species of animal. But when something is said analogically of many it is found according to its proper notion in one of them alone, from which the others are name. For example, 'healthy'...
The one and the same meaning signified by a common term when it is used univocally is here called its proper notion, that is, the combination of res significata and modus significandi the word usually bears. Thomas sometimes defines univocals in just that way: there is the same res and modus in the meaning of the name in each of its uses. By contrast, the analogous use of a term involves one res significata and several modi significandi. The first and controlling meaning is here called the ratio propria. It is a truth universally observed that when a term is used analogously, its proper notion, the primary analogate, is found in only one of the things named.
Being Is an Analogous Term
When "being" is used analogously it would have a plurality of meanings, one of which will be primary and controlling. Some such list as the following raises the problem.
 Substance is being.
 Size is being.
 Temperature is being.
Not sentences you might utter down at McDonald's perhaps, but the list is meant to make explicit a less unlikely list of statements:
[4a] Socrates is a substance.
[5a] Socrates is 5'9".
[6a] Socrates is warm.
In these sentences, various ways of being are attributed to Socrates and our initial list simply put those in the subject position. But "is substance", "is quantity", "is quality" and the like express the different modes of being which initially seemed to militate against a science of being as being.
If "being" is used analogously in such sentences, we can begin by unpacking the concrete term into "that which has existence." Then we fashion the function xExistence or "_______ existence." The res significata of being or ens is esse or existence. The modi significandi or the modi essendi will differ. One way of being, one mode of signifying existence will be primary and productive of the primary analogate or ratio propria of the term. It is because all other modes of being presuppose substantial being, but not vice versa, that substance emerges as the first and controlling meaning of the term. Thomas offers this as the ratio propria entis as it is predicated of substance: that to which existence belongs in itself and not in another. We recognize the account of substance we saw in both the Categories and in Metaphysics 7. Existence belongs to other things insofar as they relate in some way to substantial existence.
So it was that the analysis of so homely a term as "healthy" provided a second-order analysis which when applied to "being" overcame the principal objection against there being a science of being as being. Not everything that is is a substance, but whatever is is either a substance or related to it in some way that justifies calling it a being. Thus, in concentrating on substance, the metaphysician attends to that which is either meant when being is spoken of or is implied.
Suggested Reading Assignment
Selection 14, Selected Writings of Thomas Aquinas.
Suggested Writing Assignment
Compare univocal, equivocal and analogous terms, assigning the appropriate second-order or logical vocabulary to their elements.
You may want to read Aquinas on Analogy, published by the Catholic University of America Press in 1997.