As the purpose of language is to denote sensations and ideas; to mark them for our own use, or to give indication of them to our fellow men; it is obvious that the names of sensations and ideas are the fundamental parts of language. But as ideas are very numerous, and the limits of the human memory admit the use of only a limited number of marks or names, various contrivances are employed to make one name serve as many purposes as possible.
Of the contrivances for making the use of each word as extensive as possible, we have already adverted to one of great importance; that of arranging ideas in classes, and making one name stand for each individual of the class. When the classes are large, one word or mark serves to name or indicate many individuals.
But when, for the sake of economizing names, those classes have been made as large as possible, we often find occasion for breaking them down into smaller parcels, or sub-classes, and speaking of these sub-classes by themselves.
An example will render what is here expressed sufficiently plain. The term sound, is the name of a large class of ideas or sensations; for it is equally the name of both; the sound of thunder, the sound of a cannon, the whistling of the wind, the voice of a man, the howling of a dog, and so on.
{ 145} Among these sounds I perceive differences; some affect me in one way, and I wish to mark them as doing so; some affect me in another way, and I wish to mark them as affecting me in that particular way.
It is obvious that names might be invented for these subordinate classes, to mark such of them as we have occasion to mark; and the cases are numerous, in which this is the expedient adopted. Thus the term animal is the name of a large class. But we have occasion to speak apart of various portions of this class, to all the more important of which portions, we have given particular names. Horse is the name of one portion, man of another, sheep of another, and so of the rest.
There is, however, another mode of naming subordinate classes; a mode by which the use of names is greatly economized, and of which the utility is therefore conspicuous.
The subordinate class is distinguished from they rest of the greater class by some peculiarity, something in which the individuals of it agree with one another, and do not agree with the rest. Thus to recur to the example of sound. One set of sounds affect me in a certain way, a way peculiar to that set. Wishing to distinguish these sounds from others by a mark, I call them _loud_. Another set of sounds affect me in another way, and I call them _low_; a third set in another way, and I call them _harsh_; a fourth in another way, and I call them _sweet_. By means of those adjectives applied as marks upon the mark of the great class, I have the names of four species, or sub-classes; 1, loud sounds; 2, low sounds; 3, harsh sounds; 4, { 146} sweet sounds; and the number might be greatly enlarged.