The purposes of language are two. We have occasion to mark sensations or ideas singly; and we have occasion to mark them in trains; in other words, we have need of contrivances to mark not only sensations and ideas; but also the order of them. The contrivances which are necessary to mark this order are the main cause of the complexity of language. If all names were names of one sort, there would be no difficulty in marking a train of the feelings which they serve to denote. Thus, if all names were names of individuals, as John, James, Peter, we should have no difficulty in marking a train of the ideas of these individuals; all that would be necessary would be to set down the marks, one after another, in the same order in which, one after another, the ideas occurred. If all names were names of Species, as man, horse, eagle, the facility of marking the order of the ideas which they represent would be the same. If the idea man occurred first, the idea horse second, the idea eagle third; all that would be necessary would be to put down the name or mark man the first, the name or mark horse the second, and the order of marks would represent the order of ideas. But we have already seen, that the facility of communication requires names of different degrees of {160} comprehensiveness; names of individuals, names of classes, and names both of the larger and the smaller classes. For the younger and less instructed part of my readers, it may be necessary to mention, that the names of the smaller classes, are called names of Species, or specific names; the names of the larger classes, names of Genera, or generic names. Thus, the term animal, denotes a large class; a class which contains the smaller classes, man, horse, dog, &c. The name animal, therefore, is called a Genus, or a generic name; the name man, a Species, or a specific name.