Lesson 10: On Being and Essence

"And indeed the question which was raised of old and is raised now and always, and is always the subject of doubt, is just the question, what is substance?"

-- Metaphysics, 7, 1

When it has been determined that substance is the main concern for metaphysics, the primary focus of a science which has being as being for its subject, the study of substance begins. What is it? "The word 'substance' is applied, if not in more senses, still at least to four main objects; for both the essence and the universal and the genus are thought to be the substance of each thing, and fourthly the substratum" (7, 3). In the Categories, chapter 5, Aristotle distinguished primary and secondary substances. The primary substance was said to be "that which is neither predicable of a subject nor present in a subject" but "in a secondary sense those things are called substances within which, as species, the primary substances are included; also those which as genera, include the species." Particular things, on the one hand, and their universal designations on the other. So too, the substratum, the fourth item in the list given in Book Seven, is said to be that of which everything else is predicated, while it is not itself predicated of everything else. Are the first three entries to be identified with the secondary substances of the Categories?

Essence and Universal

Let us go then, you and I, to the little work Thomas wrote while still a young man, On being and essence. You will find this as selection 3 in Thomas Aquinas Selected Writings. The best modern interpretation of this work remains that of Joseph Bobik, Aquinas On Being and Essence which was first published in 1965.

A being is that which is, something concrete; its essence is that thanks to which it is and is what it is. Only things that fall into the categories will have an essence, but it is in the category of substance that essence will be found most properly. In concentrating on the essence of substance, we begin of course with material substances, substances composed of matter and form, but in metaphysics this inquiry in undertaken with an eye to being able to say something of simple substances. The question that presses upon us is this: how do matter, form and composite relate to genus, species and difference? A substance has an essence and this will be expressed by the definition that tells us what it is. The definition of a composite substance will include matter and form. If man is a substance composed of matter and form, his definition would not be matter + form, or body + soul, but rather rational animal. Why is this?

While of course there is nothing wrong with saying that a man is a composite of body and soul, we cannot predicate either taken singly of him. It would be false to say that man is matter, and it would be false to say that man is soul. These are constituents of what he is. A definition is predicated of that whose definition it is, for example, Man is rational animal, but the parts of the definition can also be predicated of the subject. We will know why. A definition would express precise knowledge of the thing defined, but we advance toward such knowledge by a series of stages. First of all we know a thing most generally, as a substance, say, then as a living substance, then as animal and finally as rational animal.

    [1] Substance is the highest genus.

    [2] Living substance is a genus.

    [3 ] Rational animal is a species.

What is the status of the predicate in those three statements. Of course, we could get rid of them and say

    [4] Man is a substance.

    [5] Man is animal.

    [6] Man is rational animal.

The predicate of [6] states the essence of man, that which is stated in his definition. The essence is what the individual has; it is what many individuals have. [6] can be exemplified by

    [7] Xanthippe is a rational animal.

    [8] Rollo is a rational animal.

    [9] Flannery O'Connor is a rational animal.

There was a time when [7], [8] and [9] were true. "Rational animal" is common to these individuals; it is something one said of many individuals. But that is the definition of universal. Is the essence a universal? That is the question.

For a number of reasons, but basically because of the demands of knowledge, Plato famously held that since the essences of things are universally common to many material individuals, they exist apart and separately from them. This is the doctrine that Aristotle denies. He found it odd to say that a thing and what it is are two things. But that is what the distinction between the individual and its essence, a distinction that must be made, seems to commit us to.

If it were indeed true that our common nouns commit us to the separate existence of essence, such separate beings would be divine, that is, changeless, and would be numbered among the things we ultimately want to know. Being and Good and One are similarly common to many individuals with which they cannot be identified and these will be the ideal entities the philosopher primarily aspires to know. On the other hand, if the claim that there are such separate entities is based on a mistake, there will have to be another and doubtless more difficult route to the knowledge of separate substances. And numbered among them will not be the separated essences of material singulars.

But how can we avoid going where Plato went? If human nature is the essence of Socrates and the essence of Plato, it could not be identical with either on penalty of their being identical with one another. But each taken singly is a human being. Plato is right, accordingly, in seeing that with such individuals and such essences, there cannot be an identity of the two. And must we not say that the difference is one between individuals and a universal? Where is human nature?

The question is rather: what is the relationship between human nature and universality. Consider the following sentences.

    [10] Man is seated.

    [11] Man is a species.

    [12] Man is rational.

All of these sentences are true. Since Socrates is comfortable in his Barca-lounger, [10] is true. [11] is also true, but what does it say? What is the meaning of "species"? The definition given by Porpyry in his Isagoge or Introduction to the Categories is this: A species is something one that is predicated of many numerically different things. A genus on the other hand is something one that is predicated of many specifically different things. In discussing these and other predicate universals -- difference, property, and accident -- as propaideutic to understanding Aristotle's Categories, Porphyry included a fateful passage.

The problem of Universals

Noting that there is disagreement between Plato and Aristotle on the status of the universals mentioned, Porphyry adds that the problem is simply too difficult to be taken up in an introductory work. There are three questions about genera and species that Porphyry formulates but will not discuss.

    * Are genera and species real or simply products of the imagination?

    * If real, are they immaterial or material?

    * If immaterial, are they present in singulars or do they exist apart?

Porphyry's became one of the auctores and hence auctoritates of the liberal arts curriculum which defined medieval education from the Dark Ages until the rise of universities and of course never entirely disappeared. The task of the scholasticus was to read (legere, lectio) the authoritative works in which one of the arts was set forth. The student could be accounted versed in an art when he understood the authoritative books passing it on to him. Porphyry's three questions -- which constitute the Problem of Universals -- were irresistible attractions to those explaining Porphyry. One can almost write the history of early medieval philosophy in terms of the various solutions that were offered to it over the centuries. Thomas Aquinas will give his solution to the problem by analyzing statements [10], [11] and [12].

If we should construct an argument, using [10] as a premise, we might get:

    [10] Man is seated.

    [10a] Plato is a man.

    [10b] Plato is seated.

[10b] might be true, Plato might be sitting in his chair, but then again he might not be, and then [10b] is false. If it is true, it happens to be true; if it false, it happens to be false.

If we did the same thing with [12], the result would be different.

    [12] Man is rational.

    [12a] Socrates is a man.

    [12b] Socrates is rational.

No problem. Why not? Rational is part of the definition of man and that of which the term can be predicated essentially will be such that the definition or its parts can be predicated of it. This is simply a way of expressing why the argument based on [12] strikes us as working, while that based on [10] makes us uneasy. We know that it isn't simply in virtue of being a man that it is true that Plato is seated. There are lots of people standing up. If any of them is seated -- or standing, for that matter -- this is true only incidentally of them insofar as they are human. This is clear, because one can be a man and be standing or not standing, seated or not seated.

If we construct a similar argument on [11], we now have some resources for assessing it.

    [11] Man is a species.

    [11a] Socrates is a man.

    [11b] Socrates is a species.

[11b] is false if to be a species means that one is predicated of many numerically different things. Lots of individuals might receive the name "Socrates", but this fellow is not predicated of anyone or anything - other than himself, perhaps, "Socrates is Socrates." For all that, [11] is true. How should we understand it. When we said that [10] was true, we agreed only because it happened that some individual of that nature was seated, but this was not part and parcel of his nature. It was incidentally true of human nature that it is found in a seated individual. Something like that is the explanation of the truth of [11].

A species is something one that is common to many numerically different individuals. The nature is one as it is abstracted and known by a human intellect. We know many individuals intellectually in virtue of grasping their nature or essence. As it exists, the essence is always individuated: this instance of human nature or that, Plato or Socrates. The two men are really similar of course, for reasons having to do with physics and biology. In grasping their similarities, especially their essential similarity, the mind forms a notion which is signified by the common term "man." The many individuals are truly called men because the nature is truly found in them. But it is only one and distinct from the individuals as it is known. It is not numerically the same nature that is found in Socrates and Plato. The nature owes its unity, its abstraction from individuating notes and its predicability to the mind. These are true of it insofar as it is known by us. They are incidentally true of the nature. That means that "to be predicated of many" is not part of the essence of man. If it were, the argument we constructed on [11] would work and [11b] would be true. But it is false. The argument seeks to predicate of the individual something that is only incidentally true of the nature as it is known.

If we should say that words like "universal," "genus," "species" and the like are second-order words, whereas words like "Socrates," "man" and "seated" are first order terms, we would know what we mean. First order terms stand for things as they are: they are, Thomas would accordingly say, first intentional. The second-order terms mentioned do not stand directly for things as they exist, but only as they are known, talked of, predicated, and the like. In the light of this, we can see why Thomas Aquinas sums up Aristotle's complaint against Plato by saying that the latter confused the order of being with our order of understanding.

Such considerations as these are part of the effort to understand substance as it is found in compound things. The point of the analysis, again, is to arrive at knowledge of separated substances. Such knowledge is said to be acquired on analogy with material substances. It is to that claim that we must now turn.

Suggested Reading Assignment

Read all of On being and essence which is Selection 3 in the Penguin Selected Writings of Thomas Aquinas.

Suggested Writing Assignment

What is the "problem of universals" and what is Thomas's solution to it?


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