[Article] The Logical Terms of Sense Realism

A Thomistic-Aristotelian & Phenomenological Defense

Daniel C. Wagner
Professor and Chair of Philosophy
Aquinas College, Grand Rapids, MI
Editor, Reality

ABSTRACT: At the heart of realist philosophy is the doctrine of univocal predication of definitions or the universal terms genus, species, and difference. This doctrine, first set down by Aristotle in the Categories, was famously rejected in the medieval period by William of Ockham. Ockham’s nominalism consisted in the claim that all that is common when a term is predicated of particular individuals is the term or name (nomen) and not essential meaning or nature. His position was accepted by virtually all the major modern philosophers, and still stands as one of the most formidable obstacles to realism.

After giving a detailed textual presentation of Aristotle’s treatment of definition—the logical terms of sense-realism—in the Topics and Categories, this article offers a critical defense of the doctrine of univocal predication in two stages. First, by analysis of the phenomenon of predication as it is exercised in human language, it shown that the nominalist position is untenable by reductio ad impossibile: nominalism results in contradiction as human knowers do not predicate names and conceptual meaning unless they suppose the truth of the doctrine of univocal predication. Second, looking to key texts in Aristotle, and inspired by Avicenna and St. Thomas Aquinas, a plausible account of the identity between individuals and universal definitions is articulated, which avoids the major criticism of univocal predication offered by nominalists, i.e., that the doctrine reduces to contradiction in equating individuals and universals. Form provides a principle of identity between individuals and universal, as the same form can be conceived in two modes of existence: (i) in the individual and (ii) as a separated universal. The critique of nominalism offered in defense of sense-realism is taken up under the umbrella of the phenomenological method. Beginning from an attitude of neutrality regarding the question of whether or not definitions signify what is real in the particulars of sense-experience, the profound unreasonableness of nominalism is exhibited while the sense-realism of Aristotle and St. Thomas Aquinas is shown to be the most reasonable account of the phenomena.

[read the response by james capehart, “the philosophical implications of sense realism”]

Table of Contents:

  1. Introduction
  2. Primary Terms of Classical Sense-Perceptive Realism: Aristotle’s Topics and Categories
    1. Definition propositions in the Topics
    2. Predication and reality
    3. Primary and secondary being
  3. A Brief History of the Problem of Universals & Nominalism
  4. An Aristotelian-Phenomenological Defense of Secondary Being & Univocal Predication
    1. A reductio ad impossibile argument against nominalism
    2. An Aristotelian account of univocal
  5. Conclusion
  6. References

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1. Introduction

As the introduction to this issue of Reality has explained in some detail, philosophical realism, in the broadest of terms, “means that (i) there is reality—that things actually exist in the world—and (ii) that we can comprehend and express true (or conversely false) statements/propositions about this reality.” So, for example, the realist holds that a buzzing being with a stinger, collecting nectar, really exists over there on the flower and that I express knowledge of this being when I apply the name ‘honey bee’ and its corresponding definition to this buzzing being, distinguishing it from the flower, the pond, the frog, the lily, etc. In answering the question “what is realism” in a manner sensitive to the historical fact that the essential tenets of realism have been, and especially now are, often rejected, it will be helpful to think of realism as a problem in light of this general meaning. Setting out the correct problem is of the utmost import.

Broadly speaking, one might say that the problem lies in explaining how it is that we can know there is reality and how it is that this reality comes to exist in the mind in such a way that the mind can know and express it as it is. So, to stick with our example, the problem would lie in explaining how it is that I come to possess the notion that the buzzing being is over there on the flower and then apply the name ‘honey bee’ to it understanding that what it is in itself is captured by the definition corresponding to the name. Given the formulation of the problem in this manner, one might then immediately attempt to give a genetic account of knowledge, that is explaining the genesis of knowledge of things in the world beginning with sensation through the sense organs and culminating in abstract understanding of things sensed in the world—the move from the buzzing being to the definition of the honey bee and its application in judgement. Given the widely accepted Modern, Cartesian-idealist assertion that what the mind knows is not things in the world but ideas, concepts, impressions, or, as David Hume says, “copies,” of those things which exist only immanently in the mind, the urgency of giving a genetic account of human knowledge seems even greater.[1] If my knowledge that the buzzing being is a honey bee is true because my idea of the honey bee is an accurate “copy” of the honey bee itself, then it seems that I must first give an account of how I came to possess this idea in such a manner as to explain its truthful accuracy in relation to the thing I apply it to in the act of judgment. On this “impression-to-thing-itself” model of knowledge, if one cannot account for accurate concept formation, then, one cannot be sure that what one thinks one knows (that the buzzing being on the flower is a honey bee) is true.

But then, perhaps, the genetic account is not quite the fundamental problem, and we have jumped the gun, as it were. While a comprehensive account of the genesis of the abstract meanings, ideas, or concepts that make knowing possible is important and necessary for a complete explanation and defense of sense realism, moving immediately into this account would be a hasty methodological error. To begin, this approach falsely suggests that, if one could not give a comprehensive account of all the possible details of the genesis of knowledge in physical, psychological, and mental terms, then our natural mode of assuming we know things would be naïve, illegitimate, and false. This is problematic, however, as it is motivated by the uncritical assumption that the mind knows only immanent ideas (which are “copies”) and not things in the world. In my natural attitude and mode of judging things in the world to be honey bees, lilies, ponds, and frogs, I am not even hyper-reflectively focusing on the concepts I use to form these judgments. It is a methodological error to think that the genetic account comes first in the realist approach to knowledge because, objectively speaking, human beings are already regularly engaged in thinking and speaking acts characteristic of a realist attitude using concepts as though they signify what things in the world really are. The priority, then, lies in the problem of giving an account of the terms of human knowing and expression as they present themselves in thought and language. Here, I do not mean “logical terms” in the modern sense of pure meaning abstracted from being or existence. This would, again, be to import an unfounded assumption into my analysis of the phenomena of thought and language—namely, that all logical notions can be conceived in the first place as pure meaning without a relation to being or existence in some sense. As the careful analysis to follow will bring to light, this is false. Aristotle will show us that the essential parts of human language and their syntax cannot be conceived except as through a relation to being and reality.

The methodological priority of an account of the terms of realism over the genetic account becomes even clearer through recognizing that only after one reflectively thinks about the use of terms in thought and language which constitute supposed acts of knowing things in the world can the question and problem of the genesis of such knowledge even be formulated. If, while I sit and read in this garden by this pond, I have not already made the intellectual judgement ‘that buzzing being is a honey bee,’ I cannot yet even ask the question of whether or not my application of this predicate ‘honey bee’ to this subject ‘buzzing being’ constitutes a true expression of the way this thing (the buzzing being) is in itself. Accordingly, the primary goal of this article is the presentation and defense of the fundamental terms of reality and human knowing acts that grasp it. As it turns out, a thorough, systematic, and critical presentation of the phenomenon of human language and the terms and order of human judgement has already been conducted in antiquity by Aristotle. Thus, this article will begin in section 2 by presenting Aristotle’s treatment of logic and grammar in the Topics and Categories. Here, the primary goal will be to understand Aristotle’s division of being/substance (οὐσία/ousia) into two senses: primary, signifying (i) individual subjects existing in the world, and secondary, signifying (ii) the universal meanings by which we know primary beings, i.e., the defining terms of genus, species, and difference. Having an adequate grasp of the basic terms of realism in this manner, its most formidable historical opposition will be presented in section 3 through a historical account of the problem of universals and its culmination in the nominalism of William of Ockham, which was accepted by virtually every modern philosopher. Finally, in section 4, a defense of the logical doctrine of sense realism contra nominalism will be offered in two parts. First, following the approach of Avicenna and St. Thomas Aquinas, an Aristotelian account of the identity between primary and secondary being/substance through the principle of form (εἶδος/species) will show the plausibility of sense realism in the face of the nominalism. By appeal to form, the Aristotelian and the Thomist realist can, in fact, explain an identity and adaequatio between the knowing mind and its object. Second, it will be shown that the denial of sense realism is not reasonable, given the objective phenomenon of human language. Here, a reductio ad impossibile style argument will show that the nominalist rejection of universal meaning and realism (i.e., the denial of secondary being/substance) results in manifest contradiction and is, therefore, untenable. As Aristotle, then, performed a reductio ad vegetabilie on the sophist who would deny the principle of non-contradiction at Metaphysics IV.4, so here a similar reductio ad vegetabile will be performed on the nominalist position.

I do not share David Hume’s naiveté that any one who reflects on knowledge will see that our ideas are mere copies of things in the world.[2] To the contrary, I think, following the post-modern philosopher Edmund Husserl (1859-1938), that Hume himself needed to spend a bit more time in careful philosophical reflection. While this article presents the account of the terms of realism offered by Aristotle in antiquity, it will also operate under the umbrella of the phenomenological method, as formulated by Husserl. In the realist spirit, and in order ‘to get back to the things themselves’ in contradistinction to modern idealism, Husserl proposed using an ἐποχή (epoche), or a suspense of judgement regarding the relation of the mind to what it knows. Rather than taking a Cartesian approach, which naïvely assumes that the mind does not know things but only ideas of things, or what might be called a naïve realist approach, which uncritically takes for granted that the mind knows things in the world as they are, the ἐποχή places one in an attitude of neutrality so that candid analysis of the phenomenon of human knowing can be achieved.[3] By utilizing this methodology, Husserl achieved a necessary apprehension of the fact that human conscious knowing is essentially intentional—that it is always a relation of knower and known (noesisnoema)—thus showing the absurdity of idealist positions that divorce the mind from what is known. If the essential from and structure of human knowing is not thinking in itself without an object, as Descartes and his modern followers held, but thinking of something, the idealist descriptive account of knowing as thought alone is false.

Here, in this article, a similar approach will be taken regarding the basic terms of realism as they are set out by Aristotle. After reflective awareness of the phenomenon of judgement about things in the world through definitions, one may reasonably ask about the nature and meaning of a supposed knowing act, and may even be open to the possibility of a skepticism about whether or not he knows things in the world like honey bees in the way he naturally tends to think he knows them. Of course, I ought also to be open to the converse possibility, that critical enquiry into the matter might verify my natural realist orientation—that that is a honey bee, after all. On the other hand, it would not be reasonable for me to begin an inquiry into this phenomenon by naïvely assuming from the outset that my mind knows only immanent ideas and that these ideas or definitions of things like honey bees are not accurate representations of the things to which I suppose they correspond. By utilizing the ἐποχή, then, this study achieves the phenomenological attitude, initially taking a neutral stance regarding the application of conceptual meaning to things in the world. Indeed, the point already made above that proper methodology requires a critical treatment of the terms of realism prior to the genetic account is in line with this phenomenological method, which has us begin by examining the organic constitution of realism in the objective and publicly given phenomenon of human language, grammar, and logic.

Through an initial suspense of judgement, we hold that perhaps the realist stance described at the outset of this paper is true or perhaps it is not. After such an ἐποχή, however, it will be shown that, in fact, contradiction arises when the realist conception of the terms of defining (genus, species, and difference) is denied. A comprehensive genetic account of human knowledge, though certainly important, is not even necessary for establishing that realism is the most reasonable view of reality and human understanding—that it is absurd and self-contradictory to deny the basic tenets of realism.

2. Primary Terms of Classical Sense-Perceptive Realism: Aristotle’s Topics and Categories[4]

Categories belongs to a group of works in the Aristotelian corpus called the Organon. These works were taken to express the foundational instruments (ὄργανον/organon = instrument) by which knowledge is to be achieved.[5] If the whole of these texts together is taken as the foundational “organ” or “instrument” of knowledge, the Categories must be taken as the very footing of this foundational structure. The Categories’ primary subject matter, as Aristotle clearly indicates in chapter four, pertains to “expressions not one of which is complex,” i.e., the simple concepts which make all human thought through judgment and reasoning possible.[6] These concepts are the categories (κατηγορίαι/kategoriai), which are the simple notions communicated by linguistic terms that may be grammatically predicated of a subject through a connecting verb, forming complex judgments. Literally, and as will be explained in more detail below, they classify the concepts of the mind by which we can “accuse” beings in the world of being in some respect.[7] In what follows in this section, a detailed and rigorous account of the first five chapters of Aristotle’s Categories will be given. The primary goal is an understanding of Aristotle’s doctrine of primary and secondary being/substance, offered in chapter 5, as this doctrine constitutes the essence of the realist approach to reality and our knowledge of it.[8]

2.1. Definitional propositions in the Topics

A brief presentation of the basic terms composing propositions expressing definitions, as Aristotle presents them in his earlier work Topics, will provide a helpful propaedeutic to our treatment of the Categories.[9] Here, treating the topic of defining, Aristotle classifies the manners in which an attribute may be said of something. For this reason, these modes of predicating are often called the “predicables.” Aristotle’s predicables are definition (ὅρος/horos), property (ἴδιον/idion), genus (γένος/genos), difference (διαφορά/diaphora), and accident (συμβεβηκὸς/sumbebekos).[10] Aristotle defines definition as “the account (λόγος/logos) signifying the essence (τὸ τί ἦν εἶναι/to ti en einai) (e.g., a human being is an animal with the capacities of reason and language.”[11] “Property” is defined as “that which does not manifest the essence of a thing, but belongs to the thing alone and is convertible with the thing,”[12] which is to say that, wherever you find the thing, you will find the property (e.g., ‘having interior angles equal to two right angles’ is a property of triangle). “Genus” is defined as “what is predicated in reference to what a thing is (ἐν τῷ τί ἐστι/en to ti esti) of several things also differing in species” (e.g., shape is the genus to which triangle, circle, etc., belong).[13] “Difference” is an essential attribute added to the genus and constituting the species (e.g., ‘with three equal sides’ differentiates the equilateral from the isosceles and the scalene).[14] Finally, an accident is neither definition, property, genus, nor difference, but it is an attribute which can belong or not belong to a thing (e.g., the tringle is blue or red or black, etc.).[15]

Most importantly, in stating the essence of a thing, the proper differences must be connected to the things’ genus. Thus, in order to define what something is through genus and specific difference one must make use of various manners of characterization. This is precisely where the categories come to the fore in the Topics, as they logically classify the various manners of characterization. Not yet distinguishing between what something is (definition) and its existence as an atomic, individual whole, separate from other things in the world—as we will see him do presently in Categories 4 and 5—Aristotle here lists 10 categories giving the first as τί ἐστι (ti esti), i.e., the ‘what it is’ or ‘definition.’[16] The other nine categories are stated in identical form to those we will treat presently in more detail in the Categories itself: quantity, quality, relation, place, time, position, possession, action, and passion.[17] Here, then, by identifying these categories, we have clearly transcended first order predication of concepts (as when one says, ‘the frog is green’) to second order predication, where concepts themselves are classified by concepts (as when I say that ‘green is a quality’). We are, then, properly in the realm of logic.

Importantly, Aristotle explains the relation between these categories and the four predicables. When a category is applied so as to signify what something is and what kind of thing it is, as in its genus or through its differentia and species, it is taken as a predicable precisely in the sense that it defines the thing. Otherwise, the predicated categorial term is merely an accident.[18] The point, then, is that while the quality ‘animal’ is predicable of a cat and a dog as a genus, ‘being in the backyard’ (place) or ‘being shaved’ (affection/quality) are predicated merely as accidents. The former generic attribute tells us what a cat and a dog are in common and essentially (living organisms in possession of nutritive and sensitive capacities), while the latter attributes are merely accidental—they could not be and then be denied of these subjects and these subjects would still be the same beings. So, knowledge pursued in rational discourse is a matter of determining how various categorial predicates are connected to the subject of inquiry, either as definitive (genus, species, difference), or as accidental (accident). Aristotle’s realism is already incipient: he believes that by appealing to the terms classified by the categories, we can know what things are essentially. To see this approach to the language and terms of realism further developed, let us turn now to Aristotle’s mature treatment of the topic in the Categories.

2.2. Predication and reality

Making it clear that the Categories is a work about knowing things in the world by definition at the very outset, Aristotle begins chapter one by distinguishing things said that are equivocal and things said that are univocal. “Things are said to be equivocal,” he says, “when only the name is common, but the account of the being [i.e., the definition] in accord with the name is different.”[19] The term ‘animal,’ for example, is predicated equivocally when it is said of the particular man and also of the picture, i.e., of a man or some other animal. The reason for this, Aristotle explains is that the definition (τί ἐστιν) of each thing termed ‘animal’ will be different (one is actually an animal, while the other is a picture).[20] On the other hand, “Something is said univocally,” he says, “when both the name is common along with the account of the being itself in accordance with the name, as in the case of both the human and the ox being animals.”[21] Aristotle further explains:

For each of these is called by the name ‘animal,’ and the account of the being of each is also the same; for, if it were demanded of one to set down what the account of the definition (τὸν λόγον τί ἐστιν) of each of these themselves is—with respect to each being an ‘animal’—one would set down the same account (τὸν αὐτὸν λόγον).[22]

Univocal predication occurs, then, when a term and the content of the definition attached to it are applied identically to a set of individual existing beings.[23] Univocal predication constitutes the foundation of realism: if univocal predication of the term ‘honey bee’ to particular buzzing beings is not possible, the realist conception of reality and knowledge is false. If all predication is equivocal, so that all that would be common to a multiplicity of buzzing beings in the garden is the name ‘honey bee’ and not an essential meaning, then my natural mode of thinking that I know such a multiplicity through an identical essential meaning is false.

Chapter two of the Categories begins by drawing a further distinction in the manner that things are said, which was already implied by the treatment of equivocal and univocal predication. When things are said equivocally or univocally there is a complex expression or, rather, expressions. Knowing the term ‘animal’ to be univocal, for example, follows on the statements, ‘The human is an animal’ and ‘The ox is an animal,’ along with the understanding that ‘animal’ means precisely the same thing in both propositions. Having these kinds of expressions as data, a further distinction may be drawn, since they can be analyzed into simple components.

1) First, there is a subject, which is that which “under-lies” (the literal meaning of ὑποκείμενον) and receives some predicable categorization of its being. ‘Subject’ can refer to an existing individual in the world and the grammatical subject of a sentence. Sometimes a grammatical subject refers to an individual being in the world, e.g., ‘Willis’ in the statement, ‘Willis is a K-9.’ ‘Subject’ may also refer, however, to a grammatical subject, which refers to a generic or specific feature, not an individual in the world, e.g., ‘animal’ in the statement ‘animal is a living organism, etc.’ 2) Second, there is the simple predicate said of the subject in order to categorize it in some manner, e.g., ‘golden’ in the statement ‘Willis is a golden.’ And, 3) third, there is some kind of connecting verb (is/belongs) linking the predicate to the subject, e.g., ‘Willis is a dog’ or ‘It belongs to Willis to have non-retractable claws.’ So, Aristotle begins by noting that, “Of things said, some are said in accord with complexity, while other things are without complexity.”[24] He then explains by way of examples. Complex sayings include a subject and a predicate, e.g., ‘the man runs’ or ‘the man wins.’ The simple sayings include the subjects, i.e., ‘man’ or ‘ox,’ along with the predicates applied to them in complex sayings, i.e., ‘runs’ or ‘wins.’[25] Definitions applied to beings, then, will be complex sayings which connect a subject to a predicate signifying what the subject is essentially. The categories will be the modes of predicating an attribute of a subject.

In the remainder of chapter two, Aristotle sets down four syntactic modes in which things can be said in relation to the subject of predication. These modes are highly relevant to the realist approach to definition, as they capture the grammatical manner in which predicates may be applied to existing things in the world depending upon whether they signify the meaning of an individual essentially and its corresponding class, or some part or accidental feature. 1) First, Aristotle notes that,

Some things are said of beings with respect to some subject, which are not in a subject, as is the case with ‘human’ being said of the subject of some [particular] human, though it is not said to be in the subject.[26]

Here, then, the mode of predication is ‘predicated of, but not present in’ a subject.

2) Second, “some things are in a subject, but are not said of a subject,” for example, a single point of grammatical knowledge is in a subject, i.e., the soul of the grammarian, but not predicable of a subject.[27] Immediately prior to giving the example, Aristotle explains what he means by ‘present in,’ shedding light on the meaning of these modes of predication, generally:

Saying ‘in a subject,’ [I refer] not to that which belongs to something as a part, but to that which in it [i.e., the subject] is incapable of separate existence.[28]

Thus, by ‘present in’ Aristotle means something which is accidental to the subject—a feature that exists only in the subject and not separately. In the first mode of predication, i.e., ‘predicated of, but not present in,’ ‘human’ is predicable of the subject ‘Socrates,’ because it signifies what he is as a human being. It is not ‘present in’ any subject precisely because it not an accidental feature of any subject that has it—it is again, precisely, what it is. On the other hand, and returning back to the second mode of predication, accidental features ‘present in’ a subject cannot be ‘predicated of’ a subject because they are not the subject—i.e., they do not belong to it as its being and what it is, but only inhere in it in such a manner as to be incapable of existence without it. Thus, we would not say ‘Socrates is grammar,’ as this would reduce Socrates to one of his accidental parts. He happens to be in possession of grammar here and now, but he was Socrates prior to possessing this attribute and he would remain Socrates also after losing it.

3) Third, Aristotle notes that, “Some things are both said of a subject and are in subject, as science is in a subject, i.e., the soul, and it is also said of a subject, e.g., grammar.”[29] 4) Fourth and finally, Aristotle states that,

Some things are neither in a subject, nor said of a subject, such as an individual human or an individual horse—for none of these types of things is in a subject or said of a subject.[30]

This mode of predication, then, pertains to the expression of individual separately existing beings. Aristotle immediately notes that, “Without qualification, things indivisible and one with respect to number are not said of a subject…”[31] Since an individual man or horse is not another individual thing, but has its own separate existence in reality, it is not predicable of any such other thing in speech. Most importantly, this rule of grammar and logic flows immediately from the nature of being and reality. Thus, for Aristotle, the logic of terms which allows for the expression of being results and is inextricable from the nature of being. The Categories is simultaneously logical and ontological in its content.[32] Without the experiential notion of an ‘individual being,’ the grammatical concept of a subject and the rules that apply to it could not be formed.[33] The nature of being is determinative of the nature of language expressing being.

Looking forward, note that the first and fourth modes of predication, i.e., (i) ‘predicated of but not present in a subject’ and (iv) ‘neither in a subject, nor said of a subject,’ will be immensely important in the Aristotelian account of definition, as will be seen in the treatment of chapter 5, where Aristotle appeal to them to in order to define the first category, “being” or οὐσία (ousia).

After a brief discussion of the rules of relation between genus, species, and subject in Categories 3, which is beyond our scope, Aristotle sets out the list of the categories by which definitions through these predicables would be obtained in chapter 4. The verb κατηγορέω (kategoreo) and its derivatives literally mean ‘to speak against’ (κατὰ + ἀγορεύω) or ‘to accuse.’ In its origins, it is a legal term. Indeed, Socrates refers to his own “accusers” in the very opening lines of his trial as κατηγοροῖ (kategoroi).[34] Thus, Aristotle’s goal is to set out the various modes of categorizing or of ‘accusing’ things of experience. He explains that he is treating simple notions or concepts and then he sets out a list of 10 such categories without delay:

Concerning expressions not one of which is complex, we signify each of the following: being (οὐσία/ousia), quantity (πόσον/poson), quality (ποιὸν/poion), relation (πρός τι/pros ti), place (ποὺ/pou), time (ποτὲ/pote), position (κεῖσθαι/keisthai), possession (ἔχειν/ekein), action (ποιεῖν/poien), and passion (πάσχειν/paskein).[35]

As is seen in the Greek, quantity, quality, place, and time are actually interrogatives or question phrases. Quantity is literally, ‘how much?’ quality, ‘of what sort?’ place, ‘where?’ and time, ‘when?’ Position, possession, action, and passion are all the infinitive forms of verbs. Position is literally, ‘to lie;’ possession, ‘to possess;’ action, ‘to act;’ and passion, ‘to be acted upon.’ Relation, which takes Aristotle some work to define in the end, is literally the prepositional phrase, ‘toward something.’ ‘Being’ or οὐσία (ousia), the first category, is an abstractive noun formed from the feminine present participle of the Greek verb to be, εἰμί (eimi).[36] Its core etymological meaning is ‘that which is one’s own,’ or ‘one’s property/belonging.’ Be aware that, while “substance” has become the standard translation of the term, as a result of Boethius’ Latin rendering (substantia) in his translation of the Categories, I will consistently use “being” here.[37]

To return to the text at hand, Aristotle proceeds to give examples for each category, and in the remainder of the work he takes up the task of defining each in itself. Aristotle provides “human” and “horse” as a “vague sketch” of what is meant by being. He does not restrict the meaning of the terms to an individual human and an individual horse.[38] This is because, as will be seen presently, he will divide the meaning of being as the first category to capture both individuals and the proper universals by which they are defined, in chapter 5. Accordingly, “human” and “horse” could here refer either to individuals or to universal meanings or definitions signifying what the individuals are as members of kinds—thus, the indication that it is a “vague and general sketch.” Aristotle gives a similar sketch of examples for the other nine categories. Examples of quantity are ‘2 or 3 cubits;’ of quality, ‘white’ or ‘grammatical;’ of relation, ‘double,’ ‘half,’ or ‘larger;’ of place, ‘in the Lyceum’ or ‘in the marketplace;’ of time, ‘yesterday,’ or ‘last year;’ of position, ‘lying’ or ‘sitting;’ of possession, ‘having shoes on’ or ‘being armed;’ of action, ‘to cut’ or ‘to burn;’ of passion, ‘to be cut’ or ‘to be burned.’[39]

When these predicates are brought into combination with each other in complex thought or propositions, an affirmation is made which, in turn, may be true or false. In and of itself “human” is not true or false, nor is “white,” “three,” or “wins.” These are simple notions of things that come to be through concept formation. Once a particular categorical term is composed with another, e.g., ‘the human is white,’ or the ‘human wins,’ i.e., where a subject is connected through a verb to a predicate, an affirmative judgment which can be characterized as true or false comes into being.[40] In general, each of the nine categories after being may be called accidents or attributes. These are sayings sayable of beings taking the role of the subject in the sentence. On the other hand, it is also true that these categories will be said of individuals at times, when the proper methodology has been used, in such a manner as to signify what they are as in their essence and definition. This point becomes clear in Categories 5, to which we must now turn in our exposition.

2.3. Primary and secondary being

Aristotle begins chapter five by explicitly drawing a distinction between being in a primary and a secondary sense, only implicit to this point. First, being in its primary sense refers to individual existing things in the world. The fourth mode of predication from chapter two provides the grammatical and logical sense of primary being:

Being (Οὐσία) is said most properly, primarily, and to the highest degree, of that which is neither said of a subject nor is it in any subject, as for example ‘this individual human’ or ‘this individual horse.’[41]

Οὐσία, thus, is a universal notion—the first of the categories to which the rest belong as predicaments—which signifies in its primary meaning the individual existing being. It is not said of a subject, because this would entail the contradiction that one individual in the world is identical with another, e.g., in the statement ‘Willis the dog is the oak tree.’ Further, such a predication would also entail the absurdity that “the oak tree, “an individual, is a universal. It is not ‘present’ in a subject, because that would entail that it be accidental, e.g., holding that ‘Willis is an accidental feature of his dog house,’ which is false, since the latter need not exist for Willis to exist as the individual he is. Primary being, then, refers to the reality of individual existing things in the world of experience as distinct from accidents.

Aristotle then sets down, however, the second sense of being. The universal terms species and genus, which are used to define primary beings by expressing what they are, are also called beings in a secondary manner:

Those things are called secondary beings (δεύτεραι οὐσίαι), however, under which as species (εἴδεσιν) the primary beings are said to belong—these and also the genera (τὰ γένη) of these species (τῶν εἰδῶν); for example, this individual human belongs under the species ‘human,’ and the species is [under] the genus ‘animal;’ therefore, these are also called secondary beings, namely, both ‘human’ and ‘animal.’[42]

Aristotle then appeals back to chapter 2, expressing that both the name and the account or definition constituting the secondary being are ‘said of a subject’—because they signify what the individual subject is. For this same reason, they cannot be present in a subject as accidents. Thus, and in line with the first mode of syntactical predication, ‘human’ and its definition, which is a secondary being, is predicated of the individual human, because “the individual human is ‘human.’”[43]

Having drawn the initial distinction between primary and secondary being in this manner, Aristotle proceeds to spell out the distinct characteristics of each, along with their commonalities and differences, in the remainder of chapter 5. The presentation that follows proceeds analytically, for the sake of clarity and concision, presenting first Aristotle’s full treatment of primary beings, and then secondary beings. However, it needs to be noted that this is not Aristotle’s procedure. Rather, he circles back and forth presenting distinctive and common features of primary and secondary beings. The reason for this lies in the reciprocal ontological and epistemological dependence of these notions upon one another, which should be kept in mind.[44]

Aristotle gives primary being absolute ontological priority over secondary being and the other nine categories. “All other things” he says, “are either said of primary beings as subjects,” i.e., as species or genus, “or are in subjects themselves,” i.e., as accidental features expressed through the other nine categories.[45] He defends this claim, here, in a manner that clearly maps onto the view of the generation of concepts (universals) that he gives in other texts (e.g., Posterior Analytics II.19, and Metaphysics I.1). Since universals are formed in the intellect by a collection of what is common to a set of individual primary beings given first to sensation, it follows that the non-existence of an essential feature in the primary beings will result in its non-existence as a secondary being, i.e., as genus or species. Simply said, were there no primary beings possessing the features meant by ‘human’ and ‘animality,’ for example, there would be no such secondary beings. Similarly, an accident cannot be said of a generic subject, except that it actually exists in the primary beings which the generic term signifies. Without individual colored bodies, for example, ‘body’ in general cannot be called ‘colored’—the accident will not exist in connection to the generic subject because it would not actually be present in any individual body.[46] Because of this, Aristotle can repeat his initial claim and conclude emphatically that primary beings are the ground of all being, i.e., secondary being and the accidents:

Thus, all other things are either said of primary beings as subjects or are in subjects themselves. Therefore, except that there have been primary beings it is not possible that any other type of beings be.[47]

Here, then, the Aristotelian logic of the terms of realism clearly holds that the primary sense of being—what is, or reality—is individual things in the world of experience. The concepts by which we know these beings are then real only to the extent that the signify what is essentially present and real in primary beings. Finally, there is the accidental type of being in the world (of which we can also form corresponding concepts through the other nine categories), which exists as dependent ontologically on primary beings.

Indicating further characteristics of primary being, Aristotle notes also that primary beings are always a ‘this one’ or individuals,[48] and for this reason they are the proper subjects, ontologically and predicatively.[49] Further, as individuals they have no contraries in themselves (e.g., there is no contrary state of being ‘a human’),[50] and they do not admit of degrees in the individual, which is to say that something either is or is not a particular primary being—the same as any other member of its species—and not more or less so.[51] Finally, primary beings are capable, while remaining numerically one and the same, of receiving contrary predicates (e.g., the same primary being can receive the contrary predicates ‘hot’ and ‘cold,’ though not in the same respect at the same time).[52] This point, of course, allows for a logical expression of change and, thus, for the possibility of a science of natural beings (one of Aristotle’s primary goals in composing the Categories, along with the other works of the Organon).

Aristotle’s treatment of secondary being occurs with constant reference to primary being as its ontological ground. Aristotle first explains that, regarding the secondary beings of species and genus, species has ontological priority, i.e., it is ‘more being,’ as it signifies most properly what a primary being is:

Of secondary beings, species is more being than genus, for it is nearest to primary being; for, if one were to state the definition (τί ἐστι) of some primary being, he will state more informatively and properly the species, rather than stating the genus.[53]

It is more informative, for example, to state that an individual is a human or a tree, than to say that it is an animal or a plant. This is because these species signify more properly what the things are in distinction from other things and, of course, they also imply and entail the generic attributes. Because of this ontological priority of species, Aristotle can further explain that just as primary beings are most properly called ‘being’ because all things are either present in them or said of them, so too species holds an analogous relationship to genera as the subject of their predication:[54]

Further, because primary beings are the subjects for all other things, and all other things are either predicated of them or are in them, they are called being especially. Nevertheless, as primary beings possess this relation to all other things, so also species holds a relation to genus; for the species is the subject for the genus; this is because the genera are predicated of the species, but the species are not conversely predicable of the genera. Therefore, from this point also, it follows that the species is more being than the genus.”[55]

With respect to species themselves, as was also the case with primary beings, no one species is more properly being than another.[56] In other words, a secondary being as signifying what a primary being is, does not admit of difference of degree. The account of the Socrates as ‘human,’ we might say, is thus equal to an account of Otis as ‘horse.’ This, again, is apparent from the relation of primary beings themselves, which secondary beings (species) signify, for “In a similar manner,” says Aristotle, “no one of the primary beings is more a being than another; for this individual man is not more a being than this individual ox.”[57] Since all the other features are accidents, they are irrelevant to the definition so that only species and genus are to be called secondary beings.

Having expressed the ontological priority of primary being to secondary, and of species to genus in this manner, Aristotle then focuses on the meaning of secondary being in relation to the logical or syntactical notions of being ‘present in’ and ‘said of.’ First, a commonality between primary and secondary being is to be noted in regard to predication: “It is common to all beings not to be in a subject.”[58] Primary beings cannot be ‘in a subject’ for they are the individual subjects—both ontologically and logically—providing the ontological and predicative foundation for all things. Secondary beings, again, cannot be ‘in a subject’ because they signify what the subject is essentially, and not accidental features.[59]

Most importantly for Aristotelian realism, not being ‘in a subject,’ secondary beings are predicated of subjects univocally:

It properly belongs to [secondary] beings and differentia to be said univocally of the things themselves of which they are said.[60]

This means that secondary beings define what primary beings are—they are, to use Aristotle’s expression from chapter 1, ὁ λόγος τῆς οὐσίας καί τί ἐστι (ho logos tes ousias kai ti esti) or “the account of the being/essence and the definition.” Defining, then, must be a matter of sorting out which attributes of a subject of enquiry belong to it essentially, and which belong to it only accidentally. Genus, species, and difference, thus, will make use of the nine categories under primary being to define it, but they will do this by signifying what properly belongs—being. So, Aristotle says,

They [i.e., secondary beings] do not simply signify any quality, such as ‘white;’ for white signifies nothing but another quality, but species and genus define (ἀφορίζει) the quality or ‘what kind’ in accord with being (περὶ οὐσίαν)—they signify the quality or ‘what kind’ (ποιὰν) with respect to being/essence.[61]

Finally, contrasting it with primary being as signifying what is individual, Aristotle further explains that secondary being is not individual itself as it is predicated of the many primary individual beings. In other words, and while it might seem that secondary beings are individuals, they are, in fact, universal meanings, common to many:

It seems that all being signifies a ‘this one’ [i.e., an individual]. In the case of primary beings it is indisputable and true that it signifies an individual, for it is signifying what is indivisible and one numerically. In the case of secondary beings, it seems similarly that they signify the individual (τόδε τι) with respect to the form of the term, when [for example] ‘human’ or ‘animal’ is said; however, this is not strictly true, but they signify quality [or ‘what kind’] (ποιόν τι)—for as a subject [of predication] a secondary being is not one as a primary being, but ‘human’ and ‘animal’ are said of many.[62]

The reason, thus, that a secondary being can be confused with a primary being as an individual is that, as Aristotle has already explained, it may be the grammatical subject of a predicate. The genus, ‘animal,’ for example may have ‘organic,’ ‘living, etc., predicated of it, and this may give the impression that it itself is an individual. The reason that this is false, Aristotle explains, is that the secondary being itself signifies a qualitative difference that is predicable of many—it cannot be an individual and serve this function qua universal at the same time.[63] Secondary beings, then, are universals apprehended in the mind, and predicated of individuals in acts of judgment and understanding.

In the Categories, Aristotle has provided the technical, i.e., logical and grammatical, foundation for a realist conception of definition. He has explained the nature of equivocal and univocal predication and expressed the logical relations of genus, species, and difference through which various subjects can be defined. The logical terms of realism and their essential connection to reality have now been set out in their locus classicus. There is reality. There are actually existing things in the world, which we are aware of and can point out in language and through sense-perceptive experience. Aristotle refers to these constituents of reality, in technical terms, as primary beings. He defines primary beings logically and grammatically, given the role that they play in human language, as ‘what is neither predicated of nor present in a subject,’ which means ontologically speaking, what is one and individuated. The conceptions of the mind which, when predicated of primary beings, constitute knowledge through propositional judgements, i.e., genus, species, and difference, though they do not exist without qualification in themselves, are real—they are being—precisely to the extent that they universally signify the essential features of primary beings and, thus, can be predicated of them univocally. Without delving into a genetic account of how human beings come into mental possession of the secondary beings that make univocal prediction possible in human knowing acts, a concise and decisive argument can be given, showing that it is entirely unreasonable to deny univocal predication and sense-realism. Such an argument is a necessary task for the realist, given the fact that, historically speaking, univocal predication as conceived by Aristotle has been seriously called into question.

3. A Brief History of the Problem of Universals & Nominalism

The position commonly called “nominalism,” which rejects univocal predication, has its focal source in the Medieval period in the thought of the logician, William of Ockham, although the question of the ontological status and reality of universals goes back at least as far as Porphyry (233-305ad). In his famous Isogoge (Εἰσαγωγή), which is an introduction to Aristotle’s Categories, Porphyry’s purpose is to help the student of Aristotle’s logic grasp the meanings of genus (γένος/genos), species (εἶδος/eidos), difference (διαφορά/diaphora), property (ἴδιον/idion), and accident (συμβεβηχός/sumbebekos). This knowledge is useful, he explains, in three ways: (1) For giving definitions; (2) for division (διαίρεσις); and (3) demonstration (ἁπόδειξις), as definitions provide the principle premises of syllogistic demonstrations. Before explaining the terms, however, Porphyry famously expresses that he will avoid certain “profound” questions, of which he lists three: (1) “Whether genera and species exist in themselves or reside in mere concepts alone.” (2) “Whether, if they exist, they are corporeal or incorporeal.” And, (3) “Whether they exist apart or in sense objects and in dependence on them.”[64]

Of course, depending on how one answers these questions, one will go in an Aristotelian, Platonic, or nominalist and anti-realist direction. In abstract logical contemplation of these questions, i.e., without thinking about the organic connection between being and the logical terms that signify it, several prominent medieval thinkers began to deny the existence of secondary being or to reduce it to mere concept. Peter of Abelard (1079-1142) followed his first teacher Jean Roscelin (1050-1125), who reduced the universal (secondary being) to a mere vocal utterance (flatus vocis, or ‘breath of the voice’). Rejecting the medieval realism of his teacher William of Champeaux (1070-1121), who held that there is something in the particular things themselves corresponding to predicated universal, Abelard famously held that universals are mere concepts, existing only in the mind. He argued from a simple disjunctive premise: either the universal (human) is partly in the particular (Socrates and Plato), or is wholly in the particular. If it is only partly present, the particulars cannot be said to be ‘human,’ and univocal predication is impossible. If it is wholly present, then it can only be present in one particular, and it cannot also be the universal. Thus, univocal predication is impossible.[65]

William of Ockham picked up and developed Abelard’s approach, and his view was accepted by virtually every modern thinker after Descartes.[66] On Ockham’s view, there are no common natures or universals at all, i.e., there are no secondary beings in the sense of conceptions that signify a common identity between a multiplicity of individuals. Ockham gives logical reasons for his denial of secondary being, similar to the argumentation of Abelard. Essentially, he deems that universals signifying a common identical essence cannot exist because the doctrine entails a contradiction: what is universal will also be individual. Thus, and with respect to the definition of the human being, at Summa Logicae I, ch. 64, Ockham notes, “‘man’ is not established except for signifying these men; it does not signify something common to them.”[67] The definition exists only conceptually, and does not have an ontological foundation in the individuals themselves since each is in fact other than each. Thus, predication of a definition over a plurality of individuals will always be equivocal. Definitions might be applied to individuals in virtue of some perceived resemblance, but are not ontologically grounded in what the individuals are. Secondary beings, then, on Ockham’s view, are not real or being in the sense that Aristotle held them to be, as they do not signify what is really common and identical among a set of particulars.

4. An Aristotelian-Phenomenological Defense of Secondary Being & Univocal Predication

In defending Aristotle’s conception of univocal predication, it is first necessary to note that his approach in the Categories is analytic: the act of disclosing the categories by which we divide and define being is itself a form of division[68] presupposing the whole or general phenomenon of the objective experience of human language and the acts of defining that occur in language. In fact, Aristotle’s approach can be treated as phenomenological. Aristotle is not arbitrarily contriving rules about the nature of human speech, communication, and the constitution of knowledge of reality by the application of definitions to primary beings. Rather, the whole of thought and language is public and already there for us to break down into its parts and syntactical order. It is a phenomenological datum. As we saw in the treatment of Categories 2, what is given is the linguistic sentence, statement, or proposition composed of subject, copula, and predicate. Aristotle does not fabricate these terms as a post hoc justification for some empirical epistemology that he has already constructed. Rather, he discovers them through the analysis of language.

This does not mean, of course, that there cannot be a development in human language and defining—indeed, Aristotle provides us with just such a development, as did Plato and Socrates, and many in the history of philosophy. Rather, the point is that human action in thought and speech already takes for granted that secondary beings are univocally predicated of primary beings. Because of this, any nominalist theory which works from abstract a priori asserted logical principles should already be highly suspect. Nominalism means that, when I predicate ‘honey bee’ of the buzzing being on the flower, and then later of another buzzing being in my window, I am not actually predicating as a result of the fact that I apprehend as ontologically present in both individuals the essential meaning of ‘honey bee.’ This, I am afraid, is quite a bizarre and absurd consequence, and it should lead us to enquire as to whether or not we might reject nominalism and find some principle for showing the identity between the universal (secondary being) and the individual (primary being) that allows us to avoid the contradiction. After all, I understand the meaning I apply to these bees and I also ‘see’ empirically that it belongs to each of them. Here, joining Aristotle in his enquiry into the categories with the post-modern phenomenological method of Husserl, we exercise an ἐποχή regarding the apparent existence of secondary being and its supposed univocal relation to primary being in acts of predication. In this attitude of neutrality, neither assuming that secondary being exists nor denying it existence, we will now discover that, in fact, human thought and language make no sense where secondary being is denied. In this attitude, by analyzing the phenomenon of defining in human language and thought, a reductio ad impossibile, or retorsive, argument can be preformed on the nominalist position, like that which Aristotle famously performed on the sophist that would deny the principle of non-contradiction at Metaphysics, IV.4.

4.1. A reductio ad impossibile argument against nominalism

In his defense of the axiomatic principle of non-contradiction, at Metaphysics, IV.4, Aristotle has shown us that one way to defend a first principle is to show the impossibility of its denial. Aristotle gives three formulations of the principle of non-contradiction, shifting from the perspective of being itself to our beliefs and propositions about being:

(1) “It is impossible for the same attribute to belong and not to belong to the same being and in the same manner at one and the same time…”[69]

(2) “For it is impossible to understand the same thing both to be and not to be…”[70]

(3) “…opposite statements are not true at the same time…”[71]

Aristotle shows that, while the sophist might signify a denial of the principle, he could not practically function in thought, speech, or action, while consistently maintaining such a denial. This is because for the denial of the principle to be true, i.e., say, that “it is false that opposite assertion are not true at the same time,” the principle must necessarily be true. The sophist then, engages in a performative contradiction, assuming the truth of what he denies. Further, and to be consistent, the sophist would have to stop thinking, speaking judgements, and acting: he could not think, e.g., ‘this is bread’ for it would also not be bread; he could not state, similarly, to himself or his friend that ‘this is bread’ because it would also not be bread; and then, he could not form an intentional desire to consume this judged to be bread, because it would also not be bread, preventing him from acting. Thus, to stay consistent, he would be reduced to the state of the vegetable—which, of course, is absurd and impossible for a human being who must think and speak presupposing the principle in order to act. In a similar manner, we can also perform a reductio ad vegetabile on the nominalist position that rejects univocal predication in denial of secondary being.[72] The predication of a singular definition over a plurality of individuals by human beings—from mundane activities like purchasing an apple at the store, all the way to the highest forms of scientific understanding regarding things like semen, ovum, elements, atoms, etc.,—is impossible and absurd to deny.

A puzzle does legitimately arise from reflection on this phenomenon as to the relation between definition (secondary being) and the individual subject of its predication (primary being). In attempting an answer to this puzzle, the nominalist may formulate the denial that the definition signifies what an individual primary being is in itself. Such a claim, however, is necessarily limited to the order of signification (ut significata). This is because, in the order of exercise (ut exercita), predication of the term is only intelligible because the one predicating believes that the attached definition signifies features that are ontologically immanent in the individual to which the definition is applied. In other words, whenever we predicate a meaning of an individual, we do so precisely because we believe that the meaning signifies what the individual is. Without this belief, it will be in principle impossible to predicate the definition at all, because a contradiction will follow: one will both have to believe that the definition signifies what the individuals are, and not believe that the definition signifies what the individuals are. In this case, of course, predication is impossible and meaningless, as are all the human activities presupposing and following on such predication.

Let us return to the honey bee example to make our point. With some study (and or a good Oxford dictionary) I could come to know in a fairly rigorous manner that a honey bee is defined as “a stinging, winged insect that collects nectar and pollen, produces wax and honey, and lives in large communities/colonies.” In this definition, the genus is insect meaning an arthropod with six legs and one or two pairs of wings. An arthropod is an invertebrate with segmented body, an exoskeleton, and jointed limbs. ‘Stinging, ‘winged,’ ‘collecting nectar and pollen,’ ‘producing wax and honey,’ and ‘living in large colonies,’ are differentia which distinguish the honey bee from other members of the same genus, and are taken from the categories of action, quality, and possession/habit.[73] Having these attributes (secondary beings) is the cause of some individuals (primary beings) in nature being honey bees. When I run into such primary buzzing beings, I know them with a very high degree of accuracy, through these secondary beings. What is key is that, any time a one has predicated a definition of a honey bee in the field, which is an expression (λόγος/logos) of his understanding it in itself and as distinct from other animals and species of its own genus, he does so precisely because he believes that the individual (primary being) displays those characteristics that are universally understood to apply to all such individuals through the relevant secondary beings (genus, species, and differentia).

This point is universalizable: predicating a definition of an individual is intelligible because the one predicating assumes that a relation of identity actually exists between the meaning of the term defining what the individual in the field is and the individual in itself. Without this belief, predication of the definition will not be possible. This is true, not only in the case of discerning honey bees in the garden, but it applies to activities as mundane as picking up trash (one must know what trash is and univocally predicate its meaning of individual pieces of trash in order to pick it up), and as complex as scientific research into things like light, the stars and the planets, animals, atoms and quarks, and so on. The only way to explain the phenomenon that natural scientists formulate their subject matter through formally defining characteristics, is to accept the Aristotelian account of secondary being and univocal predication. That scientists actually disclose the specifying characteristics of a particular subject allowing for demonstrative conclusions, is only possible because they determine those characteristics shared in common by the individuals who are members of the subject genus being studied. Without univocal predication, what scientists do when they define animals, elements, forces, etc., would be impossible. The nominalist might signify a denial of univocal predication of definitions. However, candid analysis of the phenomenon of the predication of definitions over individuals shows that such a denial is, in practice, absurd and impossible. Like the sophist that would deny the principle of non-contradiction, therefore, the nominalist is reduced in his position to the state of the vegetable.[74] If the nominalist needs to purchase an apple at the store, to be consistent, he will not be able to do so, since he will not be able to distinguish the apple from anything else. Examples such as this showing the impossibility of nominalism in human action are as infinite as the circumstances surrounding human existence. The state of neutrality with which we began this enquiry, then, must be abandoned: we can be as certain that secondary beings exist and allow for univocal predication as we are (with Aristotle) that the principle of non-contradiction must be true, since absurdity follows from denying its reality.

4.2. An Aristotelian account of univocal predication

While it is clear that univocal predication must be accepted as valid given the impossibility of nominalism, it is also the case that the principles necessary for explaining how univocal predication is possible need to be set out in some detail. Mainly, we must give some account of how there can be an identity between primary (individual) and secondary (universal) being without out the kind of contradiction following, which was identified by thinkers such as Ockham. Though he himself did not directly counter the nominalist position, Aristotle did provide us with such an account.

These principles are ready at hand by supplementing the treatment of Categories 5, with key texts from Metaphysics and the Physics. As has already been shown, secondary being is derivative from primary being, which is to say that its existential status is entirely dependent upon the individual primary beings it allows us to define. Holding that definitions fall under the category of being, albeit, in a secondary sense, the foundation for univocal predication of a definition is already laid. A definition is predicated univocally of each individual primary being because there is a relation of identity between the two terms: both are being (οὐσία/ousia). This Aristotelian account of definition already indicates a twofold relation of primary and secondary being. First, there must be some kind of relation of identity between the secondary being in the understanding and the primary beings of which it is predicated. Second, there must be a relation of primary beings to one another understood as having the same essence, the account of which is the definition. The appropriate question now becomes: what principle could provide the basis for an identity between primary and secondary being, which also allows us to classify individuals as being the same kinds of things?

Metaphysics, V.8, indicates the basis for this relation of identity between first and second being. “The essence (τὸ τί ἦν εἶναι), the account (λόγος) of which is a definition (ὁρισμός),” Aristotle tells us, is “called the being (οὐσία) of each thing.”[75] Even though Aristotle is clear that matter is an element of the essential subject of a physical being,[76] he nonetheless gives a special role to form as essence in the most proper sense at Physics II.3, saying that cause is said to be “the species/form and the model, which is to say the account of the essence.”[77] In the final lines of Metaphysics V.8, he then relates that being “is also separable”, we must understand, ‘from the primary being,’ “and of this nature is the shape or the species/form of each thing.”[78] The definition of a primary being is attainable through apprehension of the species/form of each thing, which though in the individual is also separable in the understanding. Species/form as such, then, can be taken to provide the basis for second being, along with the basis of the unity of the individuals making up a defined class. Essence as species/form (εἶδος) extends from primary being to secondary being and is the intelligible unity of both: εἶδος extends to both οὐσία taken in its primary sense as the particular individual[s] of sense experience and taken in its secondary sense as essence in the understanding and definition (genus, species, and difference).[79] The identity between primary and secondary being is the principle of form. This allows us to explain the phenomenon of defining, already given to us in common experience. Univocal predication is possible because 1) the form captured by the definition in the intellect is identical to that existing in the individual—though we must say, following Avicenna and St. Thomas Aquinas, in a different mode of being[80]—and, 2) because each particular primary being that is defined possesses a species/form identical to that of the other members of its class.

5. Conclusion

This article has presented a detailed account of the basic terms of sense-perceptive realism, as they were first set down by Aristotle in the Categories. Primary beings exist in the world as individuals possessing a myriad of attributes, and we can know these beings through the categories by sorting their attributes into those that are essential and those that are accidental. In the former case, we do this through the univocal predication of concepts that are generic, specific, or differentiating, which Aristotle calls secondary beings precisely because they signify what individual members of a class really are in themselves. In the latter case, we apply concepts falling under the nine categories after being, that belong to primary beings, but which do not make them to be what they are essentially. The realist doctrine of primary and secondary being was then defended against the nominalist critique through a reductio ad impossibile style argument coupled with an appeal to the phenomenological method. Understanding that the basic terms of realism are given to us as a phenomenological datum in human language, namely, the subject, copula, and predicate composing propositions expressing judgmental understanding, we first took a stance of neutrality regarding the question of whether or not predicates taken as defining subjects of experience really captured universal and essential attributes.

It was then shown, however, by appeal to examples of the practical exercise of univocal predication in human language that the nominalist denial of secondary being is not tenable. This is because it would not be possible for us to predicate a term like ‘honey bee’ of multiple individual beings in the world, when we do predicate the term, if we did not believe or suppose that the definition (secondary being) corresponding to the term actually signified immanently possessed ontological features (species/form) of the individuals. Therefore, just as Aristotle has shown us that the denial of the principle of non-contradiction is not tenable because it results in a contradiction, so also the nominalist denial of secondary beings is not tenable, as it would have the consequence that one could not predicate a secondary being of a primary being when one actually does so in exercise or practice.

Finally, key texts of Aristotle were appealed to in order to show that, in fact, it is possible to explain the identity between universal, secondary beings and the particular individuals of which they are predicated. A singular form, species, or essence is capable of two modes of existence, one in the primary being, making it to be what it is, and one separated or abstracted in the human intellect. Thus, there is an identity and an adaequatio between the intellect and the thing/being/reality known when one, sitting in the garden, says ‘that is a honey bee.’ The form making the honey bee to be what it is in itself is identical to the species/form in the intellect which, abstracted, becomes universally predicable of all individual honey bees sharing the form. The next major task in giving an account of and defending realist philosophy will be a more complete genetic account of the formation of secondary beings in the intellect starting with sense-perception of the primary beings. This, however, is a task for another article.

[read the response by james capehart, “the philosophical implications of sense realism”]

[additional online-only response by seth kreeger, “aquinas on suppositum, essence & universals”]

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References Historically Layered

ARISTOTLE (384-322bc).

i.360-330bc. Aristotelis categoriae et liber de interpretatione, edited by L. Minio–Paluello (Oxford: Clarendon Press, 1949; reprinted in 1966).

c.348-47bc. Aristotelis analytica priora et posteriora, edited by W. D. Ross (New York: Oxford University Press, 1949).

i.348-30bc. Aristotlelis metaphysica, 2 vols, edited by W. D. Ross (Oxford: Clarendon Press, 1924; 1953 corrected edition, reprinted in 1970).

c.330bc. Aristote: Les parties des animaux, edited by P. Louis (Paris: Les Belles Lettres, 1956).

c.330bc. Aristoteles et Corpus Aristotelicum Phil., De anima “Aristotle. De anima”, edited by W. D. Ross, (Oxford: Clarendon Press 1961, reprinted in 1967).

Translations Consulted

c.360bc. Κατηγορίαι in the Basic Works of Aristotle prepared by Richard McKeon, in the English translation by E.M. Edghill, Categories (New York: Basic Books, 1941): 1-37 (complete).

Κατηγορίαι in the Loeb edition, English translation by Harold P. Cook, The Categories (Cambridge MA: Harvard University Press, 1938): 12-109.

Κατηγορίαι in the Complete Works (Aristotle) edited by Jonathan Barnes, in the English translation by J.J. Ackrill, Categories (Princeton, N.J.: Princeton University Press, 1991).

c.348-47bc. Ἀναλυτικὰ Ὕστερα in the Basic Works of Aristotle prepared by Richard McKeon, in the English translation by G.R.G. Mure, Posterior Analytics (New York: Random House, 1941): 110-186 (complete).

Ἀναλυτικὰ Ὕστερα in the Loeb edition, English translation by Hugh Tredennick, Posterior Analytics (Cambridge MA: Harvard University Press, 1960): 24-261.

Ἀναλυτικὰ Ὕστερα in the translation by Hippocrates G. Apostle, Posterior Analytics (Grinell, IA: The Peripatetic Press, 1981).

c.353bc. Τοπικά, in the Basic Works of Aristotle prepared by Richard McKeon, English translation by W. A. Pickard-Cambridge, Topics (New York: Random House, 1941).

Τοπικά, in the Loeb edition, English translation by E.S. Forster, Topics (Cambridge MA: Harvard University Press, 1960): 272-739.

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[1] Descartes commits himself to this epistemology through his mind body dualism in 1641: Meditations on First Philosophy. See, especially, Meditations I, II, and VI. David Hume describes the mind and its concepts in relation to things in the world in this manner in 1748: An Enquiry Concerning Human Understanding, §12.

[2] See, again, 1748: An Enquiry Concerning Human Understanding, §12.

[3] For Husserl’s account of the phenomenological method and the natural and phenomenological attitudes to which I have appealed throughout this introduction, see 1907: The Idea of Phenomenology and 1913: Ideas Pertaining to a Pure Phenomenology and to a Phenomenological Philosophy. For the most helpful general presentation of Husserlian phenomenology, see Robert Sokolowski’s 2000: Introduction to Phenomenology. For a general account of Husserl’s method and epistemological accomplishments in contrast to the Cartesian approach, and for an account of the compatibility of Aristotelian and Thomistic sense-perceptive realism with phenomenology, see also, Daniel C. Wagner 2019: “On the Foundational Compatibility of Phenomenology & Thomism,” in Studia Gilsoniana (forthcoming).

[4] Significant portions of the treatment of Topics and Categories, here, along with the argument in defense of Aristotle’s realist conception of definition are taken from chapter 2 of my dissertation, 2018: φύσις καὶ τὸ ἀνθρώπινον ἀγαθόν: The Aristotelian Foundations of the Human Good, 83-117, available through ProQuest. Hereafter, the work will simply be referred to as The Aristotelian Foundations of the Human Good.

[5] This follows the organization of the Aristotelian corpus by Andronicus of Rhodes in the 1st century B.C. See, E.S. Forster’s 1960 introductory essay to the Loeb edition of the Topics, 266.

[6] Aristotle i.360-330bc: Categories, 4 (1b25): “Τῶν κατὰ μηδεμίαν συμπλοκὴν λεγομένων…” This passage will be treated in more detail below. Aristotle’s Greek is taken from Aristoteles et Corpus Aristotelicum Phil., ed. by W.D. Ross (Oxford: Clarendon Press, 1950, Repr. 1966). All translations are my own, unless indicated otherwise.

[7] Though it is beyond the scope of the current study, it must be acknowledged that Aristotle develops and contributes to a tradition on categories going back through his teacher, Plato, to Socrates and the pre-Socratic traditions on oratory, mathematics, and medicine. For a recent treatment of definition, division, and classification in Socrates, Plato, and the pre-Socrates, and for comparison and contrast of Aristotle’s approach to his predecessors, see chapters 1 and 2 of The Aristotelian Foundations of the Human Good.

[8] I am much indebted to Michael W. Tkacz, who first made this fact known to me in his treatment of the problem of universals in Medieval philosophy.

[9] Following Jonathan J. Sanford 2004: “Categories and Metaphysics: Aristotle’s Science of Being”, 6, and contra the view of Michael Frede 1981: “Categories in Aristotle”, it is not necessary to give a full treatment of Topics in order to grasp the Categories. The appeal here is limited to the extent that it is helpful for understanding the Categories. In point of fact, the Topics is a less mature work of Aristotle, often reflecting Platonic accounts of division (thus, the primary concern is “dialectic”). One should give priority to Categories in treating Aristotle’s approach to definition (along with Posterior Analytics, and De partibus animalium). On this latter claim, see E.S. Forester’s introduction to his 1960 translation of the Topics, in the Loeb edition, 265-269. For an analysis showing that the Topics represents an earlier, less developed stage of Aristotelian logic in comparison to the Categories and the Analytics, see C.M. Gillespie 1925: “The Aristotelian Categories”, 77-79. Regarding the claim that the Topics reflects Platonic division, c.f., again, Gillespie’s 1925: “The Aristotelian Categories,” 76-77. One fairly obvious indication of this fact is that when Aristotle gives a complete list of the categories in c.353bc: Topics, I.9 (103b20-24), he lists the first category as τί ἐστι, i.e., “definition” and not οὐσία, i.e., being/substance. This suggests that his interest was largely in the quiddative meaning of things, like his teacher Plato, as it does not manifest the radical break of the Categories by making concrete existing individuals of experience the basis of reality and knowledge. For more on the topic of definition and division and the relation of the Topics to the Categories, see, The Aristotelian Foundations of the Human Good, chapter 2, sec. A.

[10] See c.353bc: Topics, I.4 (101b17023): “Now, every premise and problem manifests either property, genus, or accident; for one must also arrange difference—being generic—together with genus. However, since one sense of property signifies essence, and another does not signify essence, let property be divided into both the priorly mentioned parts, and let that sense called the essence signify the definition, and the remaining sense let us call property according to commonly rendered language.” Or, πᾶσα δὲ πρότασις καὶ πᾶν πρόβλημα ἢ ἴδιον ἢ γένος ἢ συμβεβηκὸς δηλοῖ· καὶ γὰρ τὴν διαφορὰν ὡς οὖσαν γενικὴν ὁμοῦ τῷ γένει τακτέον. ἐπεὶ δὲ τοῦ ἰδίου τὸ μὲν τὸ τί ἦν εἶναι σημαίνει, τὸ δ’ οὐ σημαίνει, διῃρήσθω τὸ ἴδιον εἰς ἄμφω τὰ προειρημένα μέρη, καὶ καλείσθω τὸ μὲν τὸ τί ἦν εἶναι σημαῖνον ὅρος, τὸ δὲ λοιπὸν κατὰ τὴν κοινὴν περὶ αὐτῶν ἀποδοθεῖσαν ὀνομασίαν προσαγορευέσθω ἴδιον.

[11] See c.353bc: Topics, I.5 (101b38-102a): ἔστι δ᾿ ὅρος μὲν λόγος ὁ τὸ τί ἦν εἶναι σημαίνων.

[12] c.353bc: Topics, I.5(102a18-19): Ἴδιον δ’ ἐστὶν ὃ μὴ δηλοῖ μὲν τὸ τί ἦν εἶναι, μόνῳ δ’ ὑπάρχει καὶ ἀντικατηγορεῖται τοῦ πράγματος. Aristotle’s example here is that a human has the property of being grammatical.

[13] c.353bc: Topics, I.5 (102a31-32): Γένος δ’ ἐστὶ τὸ κατὰ πλειόνων καὶ διαφερόντων τῷ εἴδει ἐν τῷ τί ἐστι κατηγορούμενον.

[14] c.353bc: Topics, I.9 (103b15-16): …ἐπειδὴ ὁ ὁρισμὸς ἐκ γένους καὶ διαφορῶν ἐστιν· Or, “…since the definition is [formed] from the genera and differentia.” See also, Topics VI.1 (139a28-29) δεῖ γὰρ τὸν ὁριζόμενον εἰς τὸ γένος θέντα τὰς διαφορὰς προσάπτειν· Or, “For the one defining must have set it [i.e., the defined] into a genus to then ascribe differences.”

[15] c.353bc: Topics, I.5 (102b4-7): Συμβεβηκὸς δέ ἐστιν ὃ μηδὲν μὲν τούτων ἐστί, μήτε ὅρος μήτε ἴδιον μήτε γένος, ὑπάρχει δὲ τῷ πράγματι, καὶ ὃ ἐνδέχεται ὑπάρχειν ὁτῳοῦν ἑνὶ καὶ τῷ αὐτῷ καὶ μὴ ὑπάρχειν· Or, “An accident is that which is not one of these things, neither the definition, nor a property, nor genus, but still belongs to a thing, and it is also that which can belong to any one and self-same thing whatsoever and not belong [to it].”

[16] c.353bc: Topics, I.9 (103b22).

[17] c.353bc: Topics, I.9 (103b22-23): … ποσόν, ποιόν, πρός τι, ποῦ, ποτέ, κεῖσθαι, ἔχειν, ποιεῖν, πάσχειν.

[18] Cf. Sanford 2004: “Categories and Metaphysics: Aristotle’s Science of Being”, 6-12.

[19] i.360-330bc: Categories, 1 (1a1-3): Ὁμώνυμα λέγεται ὧν ὄνομα μόνον κοινόν, ὁ δὲ κατὰ τοὔνομα λόγος τῆς οὐσίας ἕτερος, οἷον ζῷον ὅ τε ἄνθρωπος καὶ τὸ γεγραμμένον·

[20] i.360-330bc: Categories, 1 (1a4-6): ἐὰν γὰρ ἀποδιδῷ τις τί ἐστιν αὐτῶν ἑκατέρῳ τὸ ζῴῳ εἶναι, ἴδιον ἑκατέρου λόγον ἀποδώσει. Or, “For, if one were to set down the definition of these with respect to each being called an ‘animal,’ one will set down a different account of each.”

[21] i.360-330bc: Categories, 1 (1a6-8): συνώνυμα δὲ λέγεται ὧν τό τε ὄνομα κοινὸν καὶ ὁ κατὰ τοὔνομα λόγος τῆς οὐσίας ὁ αὐτός, οἷον ζῷον ὅ τε ἄνθρωπος καὶ ὁ βοῦς· Following Harold P. Cooke, E.M. Edghill and Fr. Owens, I have rendered ὁμώνῠμος and συνώνῠμος ‘equivocal’ and ‘univocal,’ not giving the literal equivalents of ‘homonymous’ and ‘synonymous.’ As Owens points out, the definitions given at Categories, 1 are not of terms, to which ‘homonymous’ and ‘synonymous’ refer alone in English, but to the things denoted by the terms. This is clear immediately in the definition of things that are ὁμώνῠμος. The name or term is, in fact, common to the things, which differ in what they are in their being. See Owens 1978: The Doctrine of Being in the Aristotelian Metaphysics, 112. For the alternative translation, see J.J. Ackrill’s translation of Categories in the Complete Works (Aristotle), 2.

[22] i.360-330bc: Categories, 1 (1a8-12): τούτων γὰρ ἑκάτερον κοινῷ ὀνόματι προσαγορεύεται ζῷον, καὶ ὁ λόγος δὲ τῆς οὐσίας ὁ αὐτός· ἐὰν γὰρ ἀποδιδῷ τις τὸν ἑκατέρου λόγον τί ἐστιν αὐτῶν ἑκατέρῳ τὸ ζῴῳ εἶναι, τὸν αὐτὸν λόγον ἀποδώσει.

[23] Aristotle concludes chapter 1 by distinguishing a third manner in which things may be said, which is beyond our scope. Things may also be said as ‘derivatives’ or ‘paronyms’ (παρώνῠμος). In this case, a thing derives its name from some other name, but is different in its object than the source, as for example, says Aristotle, when ‘grammarian’ (the one who does grammar) is derived from ‘grammar,’ or the man is called ‘courageous’ by derivation from the term ‘courage.’

[24] i.360-330bc: Categories, 2 (1a16-17): Τῶν λεγομένων τὰ μὲν κατὰ συμπλοκὴν λέγεται, τὰ δὲ ἄνευ συμπλοκῆς.

[25] i.360-330bc: Categories, 2 (1a17-19).

[26] i.360-330bc: Categories, 2 (1a20-22): Τῶν ὄντων τὰ μὲν καθ’ ὑποκειμένου τινὸς λέγεται, ἐν ὑποκειμένῳ δὲ οὐδενί ἐστιν, οἷον ἄνθρωπος καθ’ ὑποκειμένου μὲν λέγεται τοῦ τινὸς ἀνθρώπου, ἐν ὑποκειμένῳ δὲ οὐδενί ἐστιν·

[27] i.360-330bc: Categories, 2 (1a23-24): τὰ δὲ ἐν ὑποκειμένῳ μέν ἐστι, καθ’ ὑποκειμένου δὲ οὐδενὸς λέγεται. Aristotle also uses the attribute ‘white’ as an example. See 1a25-29: οἷον ἡ τὶς γραμματικὴ ἐν ὑποκειμένῳ μέν ἐστι τῇ ψυχῇ, καθ’ ὑποκειμένου δὲ οὐδενὸς λέγεται, καὶ τὸ τὶ λευκὸν ἐν ὑποκειμένῳ μέν ἐστι τῷ σώματι, – ἅπαν γὰρ χρῶμα ἐν σώματι, – καθ’ ὑποκειμένου δὲ οὐδενὸς λέγεται· Or, “As, for example, a certain point of grammar is in a subject of the soul, but it is not predicated of a subject, and white is in the subject of a body—for it is from color in a body—but it is not said of a subject.”

[28] i.360-330bc: Categories, 2 (1a24-25): ἐν ὑποκειμένῳ δὲ λέγω ὃ ἔν τινι μὴ ὡς μέρος ὑπάρχον ἀδύνατον χωρὶς εἶναι τοῦ ἐν ᾧ ἐστίν

[29] i.360-330bc: Categories, 2 (1a29-1b3): τὰ δὲ καθ’ ὑποκειμένου τε λέγεται καὶ ἐν ὑποκειμένῳ ἐστίν, οἷον ἡ ἐπιστήμη ἐν ὑποκειμένῳ μέν ἐστι τῇ ψυχῇ, καθ’ ὑποκειμένου δὲ λέγεται τῆς γραμματικῆς·

[30] i.360-330bc: Categories, 2 (1b3-6): τὰ δὲ οὔτε ἐν ὑποκειμένῳ ἐστὶν οὔτε καθ’ ὑποκειμένου λέγεται, οἷον ὁ τὶς ἄνθρωπος ἢ ὁ τὶς ἵππος, – οὐδὲν γὰρ τῶν τοιούτων οὔτε ἐν ὑποκειμένῳ ἐστὶν οὔτε καθ’ ὑποκειμένου λέγεται· By the combination of the indefinite pronoun “τὶς” (tis) and the definite article “ὁ” (ho) in “ὁ τὶς ἄνθρωπος ἢ ὁ τὶς ἵππος” Aristotle is emphatically designating an individual and not a common feature predicable of an individual.

[31] i.360-330bc: Categories, 2 (1b6-9) ἁπλῶς δὲ τὰ ἄτομα καὶ ἓν ἀριθμῷ κατ’ οὐδενὸς ὑποκειμένου λέγεται, ἐν ὑποκειμένῳ δὲ ἔνια οὐδὲν κωλύει εἶναι· ἡ γὰρ τὶς γραμματικὴ τῶν ἐν ὑποκειμένῳ ἐστίν. Or, “Without qualification, things indivisible (ἄτομα) and one (ἓν) with respect to number are not said of a subject, although nothing prevents some [sorts of things] from being in subject. For, a certain point of grammar belongs to such things as are in a subject.”

[32] This interpretation mirrors that of Owens, Sanford, and also Grene. See Owens 1978: The Doctrine of Being in the Aristotelian Metaphysics, Ch. 3; Sanford 2004: “Categories and Metaphysics: Aristotle’s Science of Being;” and, Marjorie Grene 1963: A Portrait of Aristotle, 73. It is at odds with that of David Sachs, G.E.L. Owen, Michael Frede, C.M. Gillespie, Walter E. Wehrle. Sachs opts for reading Categories as merely a work in logic (David Sachs 1948: “Does Aristotle have a Doctrine of Secondary Substance?” 221-225). G.E.L. Owen sees Categories as fundamentally metaphysical in its content in 1986: “Logic and Metaphysics in Some Earlier Works of Aristotle”, 180-199; cf. Michael Frede holds a similar view. C.M. Gillespie, and Walter E. Wehrle, hold that Categories is logical in its contents in 1925: “The Aristotelian Categories” and 2000: The Myth of Aristotle’s Development and Betrayal of Metaphysics, respectively (again, cf., Sanford). There is also the erroneous and modernistic view that Aristotle “invented” the categories, grounded in epistemological relativism and subjectivism. See, e.g., Fredrick J.E. Woodbridge 1965: Aristotle’s Vision of Nature, 7. Ackrill articulates the correct position extremely well, in his introductory remarks to the Categories. The primary goal of Aristotle is to provide a logical structure for the sciences of φυσις (nature) and τὰ ὄντα (existing things) in general. Thus, Categories is not just about names and their relations, but it is about the things that names signify. Categories is not merely a linguistic and logical work: “Aristotle relies greatly on linguistic facts and test, but his aim is to discover truths about non-linguistic items.” We can add to this point the fact that for Aristotle, a treatment of language which is to express what is true of beings in the sciences is in principle inseparable from being. This is because being determines the structure and meaning of language whenever it expresses what is true. i.348-30bc: Metaphysics, IX.10 (1051b1-10): οὐ γὰρ διὰ τὸ ἡμᾶς οἴεσθαι ἀληθῶς σε λευκὸν εἶναι εἶ σὺ λευκός, ἀλλὰ διὰ τὸ σὲ εἶναι λευκὸν ἡμεῖς οἱ φάντες τοῦτο ἀληθεύομεν. Or, “For it is not because we think truly that you are white that you are white, but rather it is because you are white that we are speaking this assertion truly.” Cf. Owens 1978: Doctrine of Being, 138.

[33] John Herman Randall, Jr. has suggested that Aristotle held that “the structure of Greek language and the structure of the world are ultimately the same…” Charitably, Randall does point out that Aristotle’s view would be no more naïve than the modern view that mathematics and the structure of the world are the same. See 1960: Aristotle, 7. However, we can see that the Categories constitutes a careful analysis of language as it follows on and is expressive of being. Aristotle is, in fact, on extremely solid ground following extremely critical analysis. If there is a human language at all, capable of conveying meaningful (i.e., true or false) statements/propositions, it will be factually the same in its basic structures as Aristotle has expressed. The fact that, perhaps, some human beings are unable to communicate being in language at the level of the Greeks, Latins, Germans, English, etc., is, of course, no evidence at all that language is not as Aristotle says it is at it base. It merely shows that there may be some cultures lacking the more complete expression of being.

[34] Plato, Apology (17a1-2): Ὅτι μὲν ὑμεῖς, ὦ ἄνδρες Ἀθηναῖοι, πεπόνθατε ὑπὸ τῶν ἐμῶν κατηγόρων, οὐκ οἶδα· Or, “What you, oh Athenian men, have experienced at the hands of my accusers, I have no idea.”

[35] i.360-330bc: Categories, 4 (1b25-27): Τῶν κατὰ μηδεμίαν συμπλοκὴν λεγομένων ἕκαστον ἤτοι οὐσίαν σημαίνει ἢ ποσὸν ἢ ποιὸν ἢ πρός τι ἢ ποὺ ἢ ποτὲ ἢ κεῖσθαι ἢ ἔχειν ἢ ποιεῖν ἢ πάσχειν.

[36] For a helpful treatment of the term οὐσία and the history of its various translations in Latin and English, see Fr. Joseph Owens, The Doctrine of Being in the Aristotelian Metaphysics, 139. See Also, R.E. Houser, “The Language of Being and the Nature of God in the Aristotelian Tradition,” in Proceedings of the ACPA, Vol. 84., 2011, 117.

[37] See, for example, Boethius c.509-11: Aristoteles Latinus: Aristoteles: Categoriae, c.5: “Substantia [οὐσία] autem est, quae proprie et principaliter et maxime dicitur, quae neque de subiecto praedicatur neque in subiecto est, ut aliqui homo vel aliqui equus.” Or, “Now, substance is, which is said properly, primarily, and in the highest degree, that which is neither predicated of a subject, nor is it in a subject, as for example a particular human or a particular horse.” For my argument as to why, though it is not a perfect translation, “being” is still the best translation of οὐσία over and above the alternatives, including the standard “substance,” see Wagner 2018: The Aristotelian Foundations of the Human Good, Chapter 2, 104-109.

[38] i.360-330bc: Categories, 4 (1b27-28): ἔστι δὲ οὐσία μὲν ὡς τύπῳ εἰπεῖν οἷον ἄνθρωπος, ἵππος· Or, “To speak in the manner of a vague or general sketch, being is, for example, human or horse.”

[39] i.360-330bc: Categories, 4 (1b28-2a4): ποσὸν δὲ οἷον δίπηχυ, τρίπηχυ· ποιὸν δὲ οἷον λευκόν, γραμματικόν· πρός τι δὲ οἷον διπλάσιον, ἥμισυ, μεῖζον· ποὺ δὲ οἷον ἐν Λυκείῳ, ἐν ἀγορᾷ· ποτὲ δὲ οἷον χθές, πέρυσιν· κεῖσθαι δὲ οἷον ἀνάκειται, κάθηται· ἔχειν δὲ οἷον ὑποδέδεται, ὥπλισται· ποιεῖν δὲ οἷον τέμνειν, καίειν· πάσχειν δὲ οἷον τέμνεσθαι, καίεσθαι.

[40] i.360-330bc: Categories, 4 (2a4-10): ἕκαστον δὲ τῶν εἰρημένων αὐτὸ μὲν καθ’ αὑτὸ ἐν οὐδεμιᾷ καταφάσει λέγεται, τῇ δὲ πρὸς ἄλληλα τούτων συμπλοκῇ κατάφασις γίγνεται· ἅπασα γὰρ δοκεῖ κατάφασις ἤτοι ἀληθὴς ἢ ψευδὴς εἶναι, τῶν δὲ κατὰ μηδεμίαν συμπλοκὴν λεγομένων οὐδὲν οὔτε ἀληθὲς οὔτε ψεῦδός ἐστιν, οἷον ἄνθρωπος, λευκόν, τρέχει, νικᾷ. Or, “Each of these predicates itself by itself is not said in the manner of affirmation, but by the combination of these in relation to one another affirmation comes to be; for every affirmation seems to be either true or false, but of things said in which there is no composition, neither is there truth nor falsity, such as is the case with ‘human,’ ‘white,’ ‘three,’ or ‘wins.’

[41] i.360-330bc: Categories, 5 (2a11-14): Οὐσία δέ ἐστιν ἡ κυριώτατά τε καὶ πρώτως καὶ μάλιστα λεγομένη, ἣ μήτε καθ’ ὑποκειμένου τινὸς λέγεται μήτε ἐν ὑποκειμένῳ τινί ἐστιν, οἷον ὁ τὶς ἄνθρωπος ἢ ὁ τὶς ἵππος.

[42] i.360-330bc: Categories, 5 (2a14-19): δεύτεραι δὲ οὐσίαι λέγονται, ἐν οἷς εἴδεσιν αἱ πρώτως οὐσίαι λεγόμεναι ὑπάρχουσιν, ταῦτά τε καὶ τὰ τῶν εἰδῶν τούτων γένη· οἷον ὁ τὶς ἄνθρωπος ἐν εἴδει μὲν ὑπάρχει τῷ ἀνθρώπῳ, γένος δὲ τοῦ εἴδους ἐστὶ τὸ ζῷον· δεύτεραι οὖν αὗται λέγονται οὐσίαι, οἷον ὅ τε ἄνθρωπος καὶ τὸ ζῷον.

[43] i.360-330bc: Categories, 5 (2a19-27): – φανερὸν δὲ ἐκ τῶν εἰρημένων ὅτι τῶν καθ’ ὑποκειμένου λεγομένων ἀναγκαῖον καὶ τοὔνομα καὶ τὸν λόγον κατηγορεῖσθαι τοῦ ὑποκειμένου· οἷον ἄνθρωπος καθ’ ὑποκειμένου λέγεται τοῦ τινὸς ἀνθρώπου, καὶ κατηγορεῖταί γε τοὔνομα, – τὸν γὰρ ἄνθρωπον κατὰ τοῦ τινὸς ἀνθρώπου κατηγορήσεις· – καὶ δὲ τοῦ ἀνθρώπου κατὰ τοῦ τινὸς ἀνθρώπου κατηγορηθήσεται, – ὁ γὰρ τὶς ἄνθρωπος καὶ ἄνθρωπός ἐστιν· – ὥστε καὶ τοὔνομα καὶ ὁ λόγος κατὰ τοῦ ὑποκειμένου κατηγορηθήσεται. Or, “It is manifest from what has been said that, regarding what is said of a subject, both the name and the account (τὸν λόγον) are predicated (κατηγορεῖσθαι) of the subject; this is the case when ‘human’ is said of an individual human, and the name is certainly predicated (for you will predicate ‘human’ of the individual human); and the account (ὁ λόγος) of ‘human’ will be predicated of the individual human—for the individual human is human. Therefore, both the name and the account will be predicated of the subject.” In contrast, and properly speaking, the definition or account of what is present in a subject, like the accidental quality, ‘white,’ cannot be predicated of the subject—even though loosely speaking the term may sometimes be predicated of the subject, as when Socrates is called white. See i.360-330bc: Categories, 5 (2a27-34). As an accidental feature, ‘white’ cannot be equated with the whole of Socrates, which is why it cannot properly be predicated of Socrates in its meaning. Here, what is meant is that Socrates is white, in his skin, not that Socrates is ‘whiteness,’ since he is not this accidental attribute.

[44] Here, in the Categories, the ontological dependence of secondary οὐσίαι on primary οὐσίαι is emphasized, and the role of secondary οὐσίαι as that by which we know the primary οὐσίαι as what they are is shown. At the same time, it is already clear that the essential forms which secondary οὐσίαι signify and are, in a way, have an ontological role to play, as Aristotle will say that primary οὐσίαι do not differ by degree. This claim is only intelligible because the primary οὐσίαι are defined by the secondary οὐσίαι, which signify or mean what they are. In Metaphysics VII, where Aristotle sets out to explain what makes primary οὐσίαι to be primary οὐσίαι, he in fact appeals to the principle of form, which makes the primary οὐσίαι to be what they are essentially and is ultimately the cause of their being the individuals that they are. The definition, of course, is an account of the form, so that now second οὐσία expresses the ontological principle making primary οὐσίαι to be the unitary things that they are. See, Michael V. Wedin, Aristotle’s Theory of Substance: The Categories and Metaphysics Zeta (Oxford: Oxford University Press, 2002). The circular dependence of these terms is benign and can be explained in terms of the order of knowledge. Sense-perception and consequent concept formation gives us a vague and better-known idea of individuals and of what they are. I do not need a rigorous definition of a pig to know that it is an individual of a certain type. This is clear from sense experience, which discloses the pig as a single organism, separated from other beings in the world, and experiment, since when the pig is cut into pieces it ceases to be a pig so that I know that it is, qua pig, an indivisible unit. When I ask, however, what makes the pig to be an individual pig, I must then appeal to the form making it to be what it is as a unity, which will require a more rigorous definition of the animal.

[45] i.360-330bc: Categories, 5 (2a34-35): τὰ δ’ ἄλλα πάντα ἤτοι καθ’ ὑποκειμένων λέγεται τῶν πρώτων οὐσιῶν ἢ ἐν ὑποκειμέναις αὐταῖς ἐστίν.

[46] i.360-330bc: Categories, 5 (2a35-2b3): τοῦτο δὲ φανερὸν ἐκ τῶν καθ’ ἕκαστα προχειριζομένων· οἷον τὸ ζῷον κατὰ τοῦ ἀνθρώπου κατηγορεῖται, οὐκοῦν καὶ κατὰ τοῦ τινὸς ἀνθρώπου, – εἰ γὰρ κατὰ μηδενὸς τῶν τινῶν ἀνθρώπων, οὐδὲ κατὰ ἀνθρώπου ὅλως· – πάλιν τὸ χρῶμα ἐν σώματι, οὐκοῦν καὶ ἐν τινὶ σώματι· εἰ γὰρ μὴ ἐν τινὶ τῶν καθ’ ἕκαστα, οὐδὲ ἐν σώματι ὅλως· Or, “This is manifest by examining the particulars; for example, ‘animal’ is predicated of ‘human,’ and therefore also of the individual human—for, if it were not predicated of individual humans, it would not be predicated of the whole of ‘human.’ Again, color is in ‘body,’ and therefore also in an individual body; for, if it were not in a particular individual, neither would it be in ‘body’ as a whole.

[47] i.360-330bc: Categories, 5 (2b3-6): ὥστε τὰ ἄλλα πάντα ἤτοι καθ’ ὑποκειμένων τῶν πρώτων οὐσιῶν λέγεται ἢ ἐν ὑποκειμέναις αὐταῖς ἐστίν. μὴ οὐσῶν οὖν τῶν πρώτων οὐσιῶν ἀδύνατον τῶν ἄλλων τι εἶναι·

[48] i.360-330bc: Categories, 5: Πᾶσα δὲ οὐσία δοκεῖ τόδε τι σημαίνειν. ἐπὶ μὲν οὖν τῶν πρώτων οὐσιῶν ἀναμφισβήτητον καὶ ἀληθές ἐστιν ὅτι τόδε τι σημαίνει· ἄτομον γὰρ καὶ ἓν ἀριθμῷ τὸ δηλούμενόν ἐστιν. Or, “It seems that all being signifies a ‘this one’ [i.e., an individual]. In the case of primary beings, it is indisputable and true that it signifies an individual, for it is signifying what is indivisible and one numerically.”

[49] i.360-330bc: Categories, 5 (2b37-3a1): ἔτι αἱ πρῶται οὐσίαι διὰ τὸ τοῖς ἄλλοις ἅπασιν ὑποκεῖσθαι κυριώτατα οὐσίαι λέγονται· Or, “Moreover, primary beings are most properly called beings because they are the subjects for all other things.”

[50] i.360-330bc: Categories, 5 (3b25).

[51] i.360-330bc: Categories, 5 (3b33-4a9), especially 4a5-8: ἡ δέ γε οὐσία οὐδὲν λέγεται, – οὐδὲ γὰρ ἄνθρωπος μᾶλλον νῦν ἄνθρωπος ἢ πρότερον λέγεται, οὐδὲ τῶν ἄλλων οὐδέν, ὅσα ἐστὶν οὐσία· Or, “ For being is not spoken of in this manner; for a human is not said to be more human now than before, nor is any other thing which is being.” This claim is not defended in the Categories. In fact, its validity is founded on the concept of φύσις (phusis) or nature. Unless primary beings have a static natural form and essential intrinsic principle of motion and rest making them to be what they are regardless of where they stand in the process of generation and corruption, they will necessarily admit of differing degrees of the species to which they belong. Of course, without the notion of nature, it would also be unintelligible to talk of such individuals as members of a species at all—which is one reason nature must be posited as a first principle in the natural sciences. In the end, without the ontological ground of nature, the concept of species itself would be nearly meaningless.

[52] i.360-330bc: Categories, 5 (4a10).

[53] i.360-330bc: Categories, 5 (2b7-10): Τῶν δὲ δευτέρων οὐσιῶν μᾶλλον οὐσία τὸ εἶδος τοῦ γένους· ἔγγιον γὰρ τῆς πρώτης οὐσίας ἐστίν. ἐὰν γὰρ ἀποδιδῷ τις τὴν πρώτην οὐσίαν τί ἐστι, γνωριμώτερον καὶ οἰκειότερον ἀποδώσει τὸ εἶδος ἀποδιδοὺς ἢ τὸ γένος·

[54] For an interesting discussion showing that primary and secondary being/substance are both the valid subject of demonstrative predication for Aristotle, see, Mary Catherine Sommers 1987: “Substance and Predication in Aristotle: A Medieval View”, 61.

[55] i.360-330bc: Categories, 5 (2b15-22): ἔτι αἱ πρῶται οὐσίαι διὰ τὸ τοῖς ἄλλοις ἅπασιν ὑποκεῖσθαι καὶ πάντα τὰ ἄλλα κατὰ τούτων κατηγορεῖσθαι ἢ ἐν ταύταις εἶναι διὰ τοῦτο μάλιστα οὐσίαι λέγονται· ὡς δέ γε αἱ πρῶται οὐσίαι πρὸς τὰ ἄλλα ἔχουσιν, οὕτω καὶ τὸ εἶδος πρὸς τὸ γένος ἔχει· – ὑπόκειται γὰρ τὸ εἶδος τῷ γένει· τὰ μὲν γὰρ γένη κατὰ τῶν εἰδῶν κατηγορεῖται, τὰ δὲ εἴδη κατὰ τῶν γενῶν οὐκ ἀντιστρέφει· – ὥστε καὶ ἐκ τούτων τὸ εἶδος τοῦ γένους μᾶλλον οὐσία. Aristotle repeats this conclusion again, at 2b29-34: Εἰκότως δὲ μετὰ τὰς πρώτας οὐσίας μόνα τῶν ἄλλων τὰ εἴδη καὶ τὰ γένη δεύτεραι οὐσίαι λέγονται· μόνα γὰρ δηλοῖ τὴν πρώτην οὐσίαν τῶν κατηγορουμένων· τὸν γὰρ τινὰ ἄνθρωπον ἐὰν ἀποδιδῷ τις τί ἐστιν, τὸ μὲν εἶδος ἢ τὸ γένος ἀποδιδοὺς οἰκείως ἀποδώσει, – καὶ γνωριμώτερον ποιήσει ἄνθρωπον ἢ ζῷον ἀποδιδούς· Or, “For good reason, thus, after primary beings, of all others, species and genera are alone called secondary being; for it is manifest that these alone are predicated of primary being; for if one were to state the definition (τί ἐστιν) of some individual human, he will more properly render a statement of the species or the genus—and more informatively, he will produce a the statement of ‘human,’ rather than ‘animal.’”

[56] i.360-330bc: Categories, 5 (2b22-24): αὐτῶν δὲ τῶν εἰδῶν ὅσα μή ἐστι γένη, οὐδὲν μᾶλλον ἕτερον ἑτέρου οὐσία ἐστίν· Or, “Of species themselves, which are not genera, no one is more a being than another.”

[57] i.360-330bc: Categories, 5 (2b26-28): ὡσαύτως δὲ καὶ τῶν πρώτων οὐσιῶν οὐδὲν μᾶλλον ἕτερον ἑτέρου οὐσία ἐστίν· οὐδὲν γὰρ μᾶλλον ὁ τὶς ἄνθρωπος οὐσία ἢ ὁ τὶς βοῦς.

[58] i.360-330bc: Categories, 5 (3a7-8): Κοινὸν δὲ κατὰ πάσης οὐσίας τὸ μὴ ἐν ὑποκειμένῳ εἶναι.

[59] i.360-330bc: Categories, 5 (3a10-21). At Categories, 5 (3a22-32), Aristotle notes also that this point applies to difference.

[60] i.360-330bc: Categories, 5 (3a33-34): Ὑπάρχει δὲ ταῖς οὐσίαις καὶ ταῖς διαφοραῖς τὸ πάντα συνωνύμως ἀπ’ αὐτῶν λέγεσθαι·

[61] i.360-330bc: Categories, 5 (3b18-21): οὐχ ἁπλῶς δὲ ποιόν τι σημαίνει, ὥσπερ τὸ λευκόν· οὐδὲν γὰρ ἄλλο σημαίνει τὸ λευκὸν ἀλλ’ ἢ ποιόν, τὸ δὲ εἶδος καὶ τὸ γένος περὶ οὐσίαν τὸ ποιὸν ἀφορίζει, – ποιὰν γάρ τινα οὐσίαν σημαίνει.

[62] i.360-330bc: Categories, 5 (3b10-18): Πᾶσα δὲ οὐσία δοκεῖ τόδε τι σημαίνειν. ἐπὶ μὲν οὖν τῶν πρώτων οὐσιῶν ἀναμφισβήτητον καὶ ἀληθές ἐστιν ὅτι τόδε τι σημαίνει· ἄτομον γὰρ καὶ ἓν ἀριθμῷ τὸ δηλούμενόν ἐστιν. ἐπὶ δὲ τῶν δευτέρων οὐσιῶν φαίνεται μὲν ὁμοίως τῷ σχήματι τῆς προσηγορίας τόδε τι σημαίνειν, ὅταν εἴπῃ ἄνθρωπον ἢ ζῷον· οὐ μὴν ἀληθές γε, ἀλλὰ μᾶλλον ποιόν τι σημαίνει, – οὐ γὰρ ἕν ἐστι τὸ ὑποκείμενον ὥσπερ ἡ πρώτη οὐσία, ἀλλὰ κατὰ πολλῶν ὁ ἄνθρωπος λέγεται καὶ τὸ ζῷον· –

[63] This concisely stated argument constitutes Aristotle rejection of a Platonic theory of Forms. Secondary beings by which we know primary beings cannot, in principle, be separately existing individuals—as Plato at times claimed they were—lest they would not be predicable of the many primary beings. This is the foundation of Aristotle’s famous 3rd man argument. The consequence of making genus and species individuals is that they no longer explain how we define members of the class; rather, they become more members of the class being defined, which results in an infinite regress. For further discussion, see Wagner 2018: The Aristotelian Foundations of the Human Good, especially 102-103.

[64] See, Edward W. Warren’s 1975 translation of the i.268-70: Isogoge, 1.

[65] See Julius R. Weinburg 1964: A Short History of Medieval Philosophy, 72-91.

[66] See John Deely’s article 2013: “Modern Epistemology and Solipsism”. Nominalism becomes severely pronounced and apparently necessary after Descartes’ ontological separation of the mind from its object[s], or perhaps better said, the things that correspond to its objects, through his reduction to the cogito and his subsequent substance or mind-body dualism. Descrates’ nominalism is captured in the following passage: “…[N]umber, when it is considered simply in the abstract or in general, and not in any created things, is merely a mode of thinking; and the same applies to all the other universals, as we call them…These universals arise solely from the fact that we make use of one and the same idea for thinking of all individual items which resemble each other: we apply one and the same term [nomen] to all the things which are represented by the idea in question, and this is the universal term. Descartes 1644: Principles of Philosophy, I.58-59, I.212, AT VIIIA.27)” This passage is taken from “Descartes Theory of Ideas,” in the Stanford Encyclopedia of Philosophy, where there is also a helpful treatment of his nominalism. Following Julius R. Weinburg, Deely has traced the modern problem of solipsism, which is first explicitly manifest in Descartes cogito ergo sum, to Ockham’s nominalist view on the category of relation. On the Ockhamist view, relations have no being independent of immanent mental awareness. They are limited to the order of ens rationis and do not extend to the order of ens reale. If this is the case, then a problem of the bridge (problema pontis) immediately presents itself, wherein we will not be able to explain how the cognitive contents of our own subjectivity (ens rationis) are related to mind independent being (ens reale) in such a manner as to account for proper knowledge of such beings. We will be left with concepts as objects of thought which have no real relation to the things of experience to which we commonly take them to correspond. Univocal predication will be impossible. See, Julius R. Weinburg 1965: Abstraction, Relation, and Induction: three essays in the history of thought. Also, for a similar discussion, see Deely’s 2001: Four Ages of Understanding: The first postmodern survey of philosophy from ancient times to the turn of the 20th century, 542-544. Finally, see Brian Kemple’s article in this issue of Reality, 2019: “Signs and Reality.”

[67] See c.1323: Summa Logicae I, ch. 64, in Opera Philosophica, vol. 1, 195: “‘homo’ non imponitur nisi ad significandum istos homines; non enim significat proprie aliquid commune eis.” The translation here is taken from Steven Striby’s dissertation 2007: Against the Principles of Nominalism. I am most grateful to Steven for his helpful guidance on the nominalism of Ockham. As he explains in his dissertation, a distinction was drawn among Scholastic logicians like Peter of Spain, William of Sherwood, and Walter Burley, between the significatum, i.e., the meaning, of a general term and its supposita, i.e., the individuals to which the term refers. The significatum corresponds to the universal form or essence, which we have seen Aristotle refer to as second being. The supposita were the particular beings which fall under the second beings. Ockham identified significatum and supposita. In this case, predication of a single term over many individuals is always equivocal. See also c.1323: Summa Logicae I, chs. 5-10, and again in chapters 33. Also, for a helpful summary of Ockham’s nominalism, see Julius R. Weinburg 1964: A Short History of Medieval Philosophy, 235-266.

[68] Cf. c.353-47bc: Physics I.1, where Aristotle explains that this is the method for obtaining knowledge of the first principles of the study of nature.

[69] i.348-30bc: Metaphysics, IV.3 (1005b19-20): τὸ γὰρ αὐτὸ ἅμα ὑπάρχειν τε καὶ μὴ ὑπάρχειν ἀδύνατον τῷ αὐτῷ καὶ κατὰ τὸ αὐτό…

[70] i.348-30bc: Metaphysics, IV.3 (1005b23-24): ἀδύνατον γὰρ ὁντινοῦν ταὐτὸν ὑπολαμβάνειν εἶναι καὶ μὴ εἶναι…

[71] i.348-30bc: Metaphysics, IV.6 (1005b23): …μὴ εἶναι ἀληθεῖς ἅμα τὰς ἀντικειμένας φάσεις…

[72] The gist of the argument given here was first given in my paper, “Definition and the Reductio ad Vegetabilium: Comments on Professor Tkacz’s Treatment of Albertus Magnus and the Error Ptolemaei,” at the Society for Thomistic Natural Philosophy Satellite session, during the National Meeting of the ACPA, Los Angeles, 2012. Professor Tkacz, inspired the phrase “reductio ad vegetabile.” Subsequently, it appeared in chapter 2 of The Aristotelian Foundations of the Human Good.

[73] I was inspired to choose this example by Plato’s treatment of definition in the Meno (72b-c). It is an interesting example, as some of the essential attributes that belong to the whole, like stinging and collecting nectar and producing honey do not belong to each individual member. So, Drones lack these attributes, which belong to the workers. Of course, the queen simply reproduces. In any case, I am not worried about this fact, here, as the definition is sufficient for identifying the worker bees, which are the ones that I am worried about getting stung by in the garden!

[74] Etienne Gilson makes a similar critique of the nominalist position in 1937: The Unity of Philosophical Experience, 4. Maritain employs the distinction between ut significata ut exercita in his critique of Husserl’s phenomenology. See Jacques Maritain 1959: Distinguer Pour Unir ou Les Degrés du Savoir, 205. Finally, in the very opening lines of his New List of Categories, Charles Sanders Peirce gives a brief argument similar to that given here for the validity of the concept/universal from the functionally fitted role that it must actually play in the unification of the sensuous manifold expressed in a proposition. Either the universal exists, or human knowledge cannot experience a unity from the sensuous manifold, which is actually expressed in the connection of a predicate to a subject through the copula. Since we do experience such a unity, thus, and express it linguistically, the universal or the concept must necessarily exist.

[75] i.348-30bc: Metaphysics, V.8 (1017b21-22): ἔτι τὸ τί ἦν εἶναι, οὗ ὁ λόγος ὁρισμός, καὶ τοῦτο οὐσία λέγεται ἑκάστου.

[76] See c.353-47bc: Physics, II.2 (193b37-194a8). Seeking to distinguish physics as an autonomous and proper science distinct from mathematics, he conveys that while mathematical objects are completely separable (χωριστὸν) in thought from matter and motion, natural subjects are separable (χωριστὸν), but to a lesser degree. This is because a complete definition of any natural subject must include its material cause.

[77] c.353-47bc: Physics, II.3 “…ἄλλον δὲ τὸ εἶδος καὶ τὸ παράδειγμα, τοῦτο δ’ ἐστὶν ὁ λόγος ὁ τοῦ τί ἦν εἶναι…” In Aristotle, it is necessary to understand that εἶδος/eidos has a twofold sense, precisely because it can signify what makes ontologically makes and individual primary being to be what it is and the definition that captures this essence. In the former case, the best way to signify its meaning in English is with the term ‘form.’ In the latter case, and given his use of the term as we have seen it in categories, the best way to signify its meaning in English is with the term ‘species.’ Often, Aristotle would like us to think of both at the same time—precisely because he is a realist, believing that the mind knows the forms making things to be what they are ontological through species.

[78] i.348-30bc: Metaphysics, V.8 (1017b24-26): ..καὶ ὃ ἂν τόδε τι ὂν καὶ χωριστὸν ᾖ· τοιοῦτον δὲ ἑκάστου ἡ μορφὴ καὶ τὸ εἶδος. Or, “…and that which, being ‘this here,’ is also separable; and such is the shape and the form of each thing.” Cf., also, De Anima, III.4 (429b10-23), where Aristotle argues that the intellect must be separate since its object, species/form, is separate. A materially individuated form, of course, cannot exist “in” the intellect.

[79] While Aristotle clearly grasps the distinction between the apprehension of essence in the understanding and its expressed definition, he appears to somewhat ambiguously apply the term second substance to both.

[80] Avicenna must be credited as the first philosopher to distinguish between two modes of existence of essence along these lines. See, The Metaphysics of the Healing, V, 1. Distinguishing between essence in the things themselves and in the intellect allows for a full resolution of the problem universals at the heart of the nominalist critique. It is the identical form and essence, though it exists in two different modes, which is how knowledge is possible. Following Avicenna, St. Thomas similarly utilizes the notion of modes of existence of essence in his dealing with universals in De ente et essentia, III.

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