Logical Universals: Predicables
The logical universal expresses the nature common to many, precisely as it is applicable to many. Our intellect considers the extension of the universal and reflects on the contents of an idea to see how it applies to its subjects precisely as a universal, that is, whether as their complete essence or only as a part of their essence or otherwise.
A logical universal differs from a direct universal. The direct universal expresses the nature of an object in the real order, in its comprehension, without considering how it applies to the individuals and the class. A direct universal is a representation of a things’s essence or nature, as we have seen.
Let’s consider some examples so this is perfectly clear.
Read the following sentence: “John is a human being.” The idea of “human being” is a direct universal because it states his essence or nature as it is found in the real order of things. John is, in fact, a human being. When we take this same sentence and say that the predicate “human being” expresses the complete essence or nature of John, we are comparing the direct universal “human being” with the subject “John” and we state how this predicate applies to the subject.
Read the following sentence: “John is an animal.” Here also, the idea of “animal” is a direct universal. When we state, however, that the predicate “animal” applies to the subject “John” as only a I of his essence or nature, then we again state how the predicate is assigned to the subject. (The predicate “animal” applies only to a part of John’s essence or nature because John is also “rational,” another predicate which also applies.)
Now we can consider the matter of predicables.
Predicables are the different modes or ways in which a universal can be predicated of its subject. There are five, and only, five possible modes. The possible modes are species, genus, differentia, property, and accident.
This is a universal idea which expresses the whole essence or nature of its subject.
Consider the sentence “John is a human being.” We are predicating the idea “human being” of the subject “John.” When we reflect on this we discover that the predicate “human being” expresses not just a part of John’s essence or nature, but the whole of his essence or nature. The idea “human being” represents the species of the idea of “John.”
Whenever we apply the idea “human being” to all human beings as a class or to the individual members of the class, this universal idea “human being” is the species.
Let’s consider another example. “Plants are organized living bodies.” The predicate of this sentence, “organized living bodies,” expresses the whole essence or nature of the idea “plant.” This predicate is its species.
A universal idea which expresses a part of the essence or nature of its subject, that part which the subject has in common with other species in this same class is called a genus.
Consider this sentence. “A dog is a living body.” The idea “living body” expresses only a part of the essence or nature of the idea “dog.” It doesn’t express the whole nature because a dog is also a sentient body. The idea “living body” can also apply to the idea “plants.”
A universal idea which expresses a part of the essence or nature of its subject, that part which distinguishes one species from another under the same genus, is called a differentia.
Consider the genus “animal.” Both “human being” and “dog” are species under this genus since “animal” applies to both. But what distinguishes the “animalness” of human being from the “animalness” of dog so that both belong to different species?
There must be some determining and differentiating essential element to limit it to the species of “human being” and “dog.” The feature which distinguishes these two ideas is the idea of “rationality.” Human beings are “rational animals” and “dogs” are “nonrational animals.”
The whole idea of “dog” is expressed by the idea “nonrational animal,” and “nonrational” is the differentia. The whole idea of “human being” is expressed by the idea “rational animal,” and “rational” is the differentia. While both human beings and dogs belong to the same genus, “animal,” they do not belong to the species, and this is because of the differentia.
The differentia narrows and limits a genus to a species.
A universal idea which expresses something which flows necessarily from the essence, though not of the essence itself, is called a property.
A property will have to be present in every individual member of a class since it is necessarily connected with the essence or nature of a thing, and can never be missing.
Consider the idea “human being.” One of the properties inherent in the essence or nature of a human being is the power of speech. Another is the ability to use written language. Still another is the ability to express oneself in a deliberately artistic manner. These are properties of “human being” necessarily connected with the essence or nature of “human being.”
One warning should be stated here. Because the power of speech or the ability to use written language are properties of the idea “human being,” does not mean that in order to be a human being one must always be able to speak or use written language. It is simply the potential to do so. A stroke victim may not be able to speak but that person still remains a human being of course. A person who has lost both arms in an accident may not be able to write but that person is still a human being. All human beings have the power of speech and the ability to use written language provided that some external or internal factor is not interfering with the capability.
A universal idea which expresses something of its subject which is neither of its essence or nature nor necessarily connected with its essence or nature, but is not necessarily connected with the essence or nature, is called an accident.
An accident is simply a nonessential element. “Being married” is an accidental element of being a human being. It is not essential to being a human being. The fact that my dog has brown eyes is not essential to his being a dog. He could have another eye color. “Brown eyes” is an accident or a nonessential element. The fact that each of us is either male or female is accidental and is not by necessity connected to our essence or nature. We are “human beings” regardless of our gender.
It should be plain now that there must exist a hierarchy of genera and species. A class may be a genus from the viewpoint of certain species below it and a species itself with reference to a class above it.
“Body,” for instance, is a species under the genus “substance” and a genus with regard to the species “living” and “nonliving” bodies below it. We, therefore, arrive at the following classification in this hierarchy. The highest genus has no other genus above it. An intermediate (subaltern) genus has at least one genus above and below it. The lowest genus has species below it, but no genus.
The highest species is the species immediately under the highest genus. The intermediate species has at least one species above and below it. The lowest species (or the species in the strict sense) has no other species, but only individuals below it. A remote genus has species below it, with at least one other genus in between; for instance, “a living body” with regard to “man,” because the genus “animal” lies between the two. A proximate genus is the one immediately above a certain species; thus “animal” is the proximate genus of “man,” since no other genus lies between them.
The direct universal has its categories and the logical universal has its predicables. The categories classify our ideas according to the things which they represent, as these things are in their own essence or nature. The predicables classify our ideas in their relation to one another.
by Jonathan Dolhenty, Ph.D.
Original article: The World of Universals