Wisdom Vault — onlinknow.co.za

meaning: it means the things to which it is applied,... it also means, in a totally different way, the qualities and peculiarities implied as being in the things. Logicians say that the number of things to which a term applies is the extension of the term; while the number of qualities or peculiarities implied is the intension.”

The extension and intension of terms has been referred to in the previous chapter. The general classification of the degrees of extension of a general term is expressed by the two terms, Genus and Species, respectively. The classification of the character of the intension of a term is expressed by the term, Difference, Property and Accident, respectively.

Genus is a term indicating: “a class of objects containing several species; a class more extensive than a species; a universal which is predicable of several things of different species.” Species is a term denoting: “a smaller class of objects than a genus, and of two or more of which a genus is composed; a predicable that expresses the whole essence of its subject in so far as any common term can express it An authority says: “The names species and genus are merely relative and the same common term may, in one case, be the species which is predicated of an individual, and in another case the individual of which a species is predicated.

Thus the individual, George, belongs to the logical species Man, while Man is an individual of the logical species Animal.” Jevons says: “It is desirable to have names by which to show that one class is contained in another, and accordingly we call the class which is divided into two or more smaller ones, the genus, and the smaller ones into which it is divided, the species.”

Animal is a genus of which man is a species; while man, in turn, is a genus of which Caucasian is a species; and Caucasian, in turn, becomes a genus of which Socrates becomes a species. The student must avoid confusing the logical meaning of the terms genus and species with the use of the same terms in Natural History.

Each class is a “genus” to the class below it in extension; and each class is a “species” to the class above it in extension. At the lowest extreme of the scale we reach what is called the infima species, which cannot be further subdivided, as for instance “Socrates”—this lowest species must always be an individual object, person or thing.

At the highest extreme of the scale we reach what is summum genus, or highest genus, which is never a species of anything, for there is no class higher than it, as for instance, “being, existence, reality, truth, the absolute, the infinite, the ultimate,” etc.

Hyslop says: “In reality there is but one summum genus, while there may be an indefinite number of infimae species. All intermediate terms between these extremes are sometimes called subalterns, as being either genera or species, according to the relation in which they are viewed.”

Passing on to the classification of the character of the intension of terms, we find: Difference, a term denoting: “The mark or marks by which the species is distinguished from the rest of the genus; the specific characteristic.” Thus the color of the skin is a difference between the Negro and the Caucasian; the number of feet the difference between the biped and the quadruped; the form and shape of leaves the difference between the oak and the elm trees, etc.

Hyslop says: “Whatever distinguishes one object from another can be called the differentia. It is some characteristic in addition to the common qualities and determines the species or individual under the genus.” Property, a term denoting: “A peculiar quality of anything; that which is inherent in or naturally essential to anything.”