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. It thus appears that, as nouns substantive are marks of ideas, or sensations, nouns adjective are marks put upon nouns substantive, or marks upon marks; in order to limit the signification of the noun substantive; and instead of its marking a large class, to make it mark a subdivision of that class. Thus the word, rose, is the mark of a large class: apply to it the adjective _yellow_, that is, put the mark yellow upon the mark rose, and you have the name, yellow rose, which is a sub-division, or species, of the class Rose. This peculiarity of naming, this putting of marks upon marks, in order to modify the meaning of a certain mark, is a contrivance which deserves the greatest attention. It is one of the principal expedients for the great purpose of economizing names, and performing the business of marking with the smallest number of marks; but, like the rest of the contrivances for this purpose, it contributes to obscure the simple process of naming; and when not distinctly known and attended to, operates as a source of confusion and error. The use of adjectives, in economizing names, is most conspicuous, in the case of those subdivisions which apply to the greatest number of classes. There is one distinction which applies to most classes; the distinction between what pleases, and what does not please us, no matter on what account. The first we call good, the second evil. These two terms serve to mark a very great number of subordinate classes, and, of course, save, to a great extent, the multiplication of names.