Cursus Philosophicus Thomisticus, Secunda Pars Artis Logicae

Logical genus is defined by Porphyry: “That which is predicated of many things differing in species in answer to ‘what?’” In this definition three points are explained:

FIRST is the character common to every predicable, in the words “that which is predicated of many”; for this is common to every predicable. Hence you will understand that the universal is not defined here materially, as a substrate, but according to the very character of universality, because that common predicate, namely “being predicated of many,” is not a nature but universality.

SECOND, what is explained in the definition, is what belongs specifically to the character of genus on the side of the term to which it is related; for relations are specified by their term. Thus the phrase “of many things distinct in species” is included, since generic universality regards these as its term.

THIRD, finally, what is explained in this definition is the mode or character of predicating, namely “in answer to what.”

As to the FIRST PHRASE: what it is to be predicated of many has been sufficiently explained above, for it belongs to the character of universality. What it is for something to be predicated of many as an essential defined thing, to which this definition belongs essentially, we will say in the next article. Hence, to explain this definition exactly, it is enough here to explain the two phrases “of many things differing in species” and “in answer to what.”

Accordingly, concerning the first phrase, “of many things differing in species,” we must say that although other predicables can be said of many things differing in species—for example, some generic differences and even generic properties are said of subjects differing in species—this is material to those predicables. Only genus, however, is predicated formally and per se of many things differing in species. For although other predicables can be predicated of many things differing in species, they are also preserved without being predicated of many things differing in species, as is clear in specific differences and properties. Thus the inferiors of such predicables need not differ in species merely because they are their inferiors. Genus, however, simply by being genus, has inferiors that differ in species, because the intrinsic character of genus expresses something contractible and divisible through specifically diverse differences. These differences are contained potentially in the genus itself and originate from it, as Cajetan rightly noted, following Albert the Great, in his commentary on this chapter on Genus¹. Hence, by its very formal character, genus requires inferiors distinct in species.

The SECOND PHRASE, namely “to be predicated in answer to what,” explains the mode and formal character of the predication of genus, insofar as it is genus.

To understand this, one must note that the phrase “in answer to what,” as St. Thomas often teaches, can ask either about a supposit or about a nature. For example, if someone asks what swims in the sea, we answer “a fish”; if someone asks what a human being is, we answer “a rational animal.” Here, when it is said that genus is predicated “in answer to what,” the second sense is meant, not the first.

Second, one must see how predication in answer to what differs from predication “as a what-sort,” not only when the latter is accidental, which is obvious, but also when it is essential, as when difference is predicated. We should not say absolutely that difference is predicated “in answer to what,” as some recent authors allow. Rather, genus is predicated “in answer to what,” and difference “as a what-sort”—that is, genus is predicated in a substantive, quidditative mode, while difference is predicated even essentially in an adjectival mode, as St. Thomas notes at the end of his treatise on Genus, chapter 2 of opusculum 48². Therefore difference is said to be predicated as an essential what-sort, or a quidditative what-sort. For although difference is essential, it nevertheless performs the office and predication of difference by way of inherence, not in the mode of a substantive, which pertains to “what.”

The reason is that the office of difference is not to provide the first foundation of quiddity, but to come to the genus and determine it so that a species is constituted. Hence it never functions as the first foundation and first character of quiddity, but as a character that contracts and comes to something else, determining it. Its mode, therefore, is to determine and actualize something previously presupposed and contractible, as genus is. Thus the substantive mode belongs to genus, while the qualificative or inhering mode belongs to difference: the former is called “what,” the latter “what-sort.” When the Philosopher said in Topics VII, ch. 3³ that both parts of a definition are predicated in answer to what a thing is, the sense is that both parts are predicated essentially, but in different modes: genus in answer to what, and difference as a what-sort.

A third distinction is considered in the very mode of predicating in answer to what: the way genus is predicated in answer to what differs from the way species is. Species is predicated in answer to what completely, because it predicates the entire and complete character of quiddity; genus is predicated in answer to what incompletely, because it predicates a constitutive part of the essence, which is potential and prior, as the foundation of the contracting difference. Both modes of signifying, however, are substantive and in answer to what.

The reason for this is that substance is signified as a whole and a complete being, since it belongs to substance to have the character of a whole and supposit. Likewise, it belongs to the mode of substance to be, as it were, underlying or foundational to other things, and to have the character of what is first in some order. From this comes the likeness by which things signified as a whole or as the foundation and first in some order are said to signify in a substantive mode. Species signifies in the mode of “what,” or in a substantive mode, because it signifies what is integral and complete in the character of quiddity. Genus, too, signifies in the mode of “what” and in a substantive mode, because it signifies in the mode of the first predicate, which is the foundation and root of the others. The definition itself explains all this when it says that genus “is predicated in answer to what of many things differing in species,” that is, as something contractible through specific differences. What is contractible is the first predicate, containing those differences potentially. The definition of species, however, says “in answer to what of many things differing in number,” thereby designating the integral character of quiddity, no longer contractible through formal and specific differences, but multiplicable through singular differences, which are material.

IF YOU ASK whether this definition of genus is essential or descriptive, the reply is that, as Porphyry presents it, it is descriptive, as he himself indicates, and St. Thomas calls it so in opusculum 48, chapter 2⁴. For the essence of genus consists in the character of universality, which regards its inferiors in such a way that they are distinct in species and are related in the mode of “what.” Its definition, however, is given through predicability, which is a property of the universal. Therefore it explains the nature of genus through a property, which makes it descriptive. It can nevertheless be reduced to an essential definition by saying: “Genus is a universal that regards (or is apt to regard, if it is defined fundamentally) many things distinct in species in answer to what.” Here the definition is given through a higher or generic predicate, namely, “universal,” and through an intrinsic difference, namely, to regard in such a way—that is, in answer to what—and to have such a term, namely, many things distinct in species.

THE ARGUMENTS ARE ANSWERED.

Against the phrase “in answer to what” it is argued: it belongs to things other than what is defined, even if predication in answer to what of many things differing in species is taken into account; and predication as a what-sort can belong to genus. Therefore the phrase is wrongly included.

The antecedent, as to its first part, is proved as follows. Being is predicated in answer to what of many things differing in species, for it is a quidditative predicate, being imbibed in the very quiddities; yet it is not a genus, since it is analogical. Definition itself is also predicated in answer to what of the defined thing; for to someone asking what a human being is, one rightly answers “a rational animal.” Difference itself, too, since it is nobler than genus, ought to be predicated in a nobler mode. But the nobler mode is predicating in answer to what—that is, predicating substantively rather than as a what-sort, which is adjectival predication in the mode of an accident. Therefore this mode ought to belong to difference as well, and not only to genus.

The second part is proved because, in the category of substance, genera and species are called secondary substances. In the chapter on Substance⁵, however, the Philosopher says that these signify a “what-sort,” and adds that genus and species determine quality with respect to substance. Therefore genus is predicated as a what-sort. Further, this predication of genus—such as “Whiteness is a color”—is nevertheless predicated through “colored,” which is predicated as inhering and consequently as a what-sort. Therefore predication in answer to what is not of the character of genus.

THE REPLY: The antecedent is denied.

To the first part the reply is that being is not a quidditative predicate, but a transcendent one, imbibed in every thing, whether or not it pertains to quiddity. Hence what is common to quiddity and non-quiddity cannot constitute a quidditative concept. The transcendent concept is therefore presupposed to the concept of quiddity; it does not constitute it, nor does it pertain more to “what” than to “what-sort.” For just as when we say “What is a human being?” and the answer is “a being,” so too, when we say “What sort is a human being?” one can answer “a being.” Moreover, because being is analogical, it is not predicated in answer to what simply and according to one character, but according to several, and only according to one proportionally; genus, by contrast, is predicated in answer to what simply and as one.

As for what is said about definition, the reply is that a definition is a complex “what” and contains not only the character of “what,” but also that of “what-sort.” For it consists of genus and difference, and is not predicated in answer to what as genus is, but in the mode of species, as an integral quiddity that it explains.

As for what is said about difference, the reply is that although it is nobler than genus on the side of the thing signified, on the side of the mode of predication it is not predicated in answer to what, because the mode of predication does not follow precisely the mode of being in the thing, but the mode of conceiving. St. Thomas teaches this in Metaphysics VII, lecture 1⁶ and opusculum 42, chapter 19⁷. Difference is conceived in the mode of what determines and actualizes, while genus is conceived as determinable and contractible. Thus genus grounds predication in answer to what in the explained mode, while difference grounds predication as a what-sort.

To the second part of the argument the reply is that the Philosopher calls secondary substances a “what-sort,” and says that they determine quality, not with respect to nature and quiddity, but in comparison with primary substances, which signify a supposit that supports them. For in relation to a supposit, species, genus, and the other higher grades all have the character of a predicate and of a form supported by the supposit. But in comparison with the nature and essence they constitute, one constitutive part, namely genus, is said in answer to what, and the other, namely difference, as a what-sort. On this solution see Cajetan on chapter 5 of the Categories.

Hence the other objection is also resolved: genus functions as a form in relation to the inferior of which it is predicated; therefore it is not predicated in answer to what, but as informing. The reply is that genus functions as a form not on the side of the thing it explains, nor in comparison with the nature it constitutes, but on the side of its mode of being a predicate, which takes on the mode of a form in relation to its subject, and in comparison with the primary substance by which it is supported. In this sense St. Thomas says in Summa theologiae I–II, q. 18, art. 7, ad 3, that genus is compared to species as something more formal, insofar as it is less contracted.

To the final proof the reply is that in the predication “White is colored,” the word “colored” is taken substantively in relation to white, although it is an adjective in relation to a body or subject of color. Hence, in relation to the subject, the predication is denominative and adjectival; in relation, however, to white, which is its inferior, it is a quidditative predication by reason of the form it signifies.

Second it is argued against the phrase “of many things differing in species.” Genus is also predicated of many things differing in number, as “animal” is of Peter and Paul; therefore the adequate term of genus is not explained in the definition.

If you say that only the immediate term is explained, which is species, an objection is raised against the predication of genus of generic individuals. For example, when “animal” is predicated of this animal and that animal, it is then predicated immediately of individuals, not of species; therefore the definition is incomplete. Also, genus can be predicated of many things differing not only in species but also in genus, as the highest genus is predicated of many intermediate genera, which are subordinate species. Therefore the phrase “of many things differing in species” does not sufficiently explain the character of genus in general.

THE REPLY is that genus is predicated of many things differing in number mediately, namely, precisely because it is predicated of many things differing in species. For since individuals are contained under a species, and whatever is predicated universally of something is predicated of everything contained under it by the principle “said of all,” genus is consequently also predicated of many things differing in number, though not as the lowest species, which is predicated immediately of them.

To the objection about generic individuals, the reply is that genus is also predicated of them mediately, whether they are contained in the same lowest species or in different ones. Generic individuals express a generic grade individualized, without expressing the specific grade through which they are contained under the generic grade. Because they do not express the specific grade but nevertheless include it, and through it belong under the generic grade, they are said to be contained mediately, although it is possible for such generic individuals to belong to different species by reason of including those species. The generic grade is always predicated of them, insofar as they are individuals, only mediately, because it is contracted and belongs to individuals mediately, even if sometimes only the generic grade is expressed and the specific grade is omitted; in this way those generic individuals are predicated.

To the second part of the argument, it is said that the highest genus is predicated of many things differing in genus, not insofar as they are genera, but insofar as they are subordinate. A genus subordinated to another, higher genus is subject to it insofar as it is a certain species, because it is subject to it insofar as it consists of that genus and a difference, which is to be a species. Hence genus is predicated of many insofar as they differ in species, because they are subject to it as species. Therefore only things that differ in category are said to differ in genus. For things within the same category differ through contracting differences and consequently constitute some species; every difference, in fact, constitutes a species.

Finally it is argued to prove that this definition is essential, because the intention of predicability is included in the character of this intention, which is genus, as St. Thomas says at the end of chapter 4 of On Being and Essence⁸. There he also adds that being predicated belongs to genus per se, since it is placed in its definition. Therefore he thinks predicability belongs essentially to the essence of genus, especially since this treatise deals per se with predicables. Thus things, insofar as they pertain to this treatise, are essentially defined when they are defined through predicability.

THE REPLY is that the meaning of St. Thomas is clear: predicability belongs to the nature of genus and belongs to it per se—either essentially, when predicability is taken as its root rather than as its own formal intention. The root of predicability, however, is universality. Or, if predicability is taken formally, it is understood to belong to genus per se and to be included in its character through per se predication in the second mode, as a property, not through per se predication in the first mode, as an essential predicate. In this treatise Porphyry deals with predicables not insofar as they are distinguished from the universal, but insofar as they are rooted in it, including the very character of universal rather than excluding it. Hence their essential definitions must also be given through the very character of universal.