The Theory of Moral Sentiments - Adam Smith [231]
It is this application of the name of an individual to a great multitude of objects, whose resemblance naturally recalls the idea of that individual, and of the name which expresses it, that seems originally to have given occasion to the formation of those classes and assortments, which, in the schools, are called genera and species, and of which the ingenious and eloquent M. Rousseau of Genevaad finds himself so much at a loss to account for the origin.3 What constitutes a species is merely a number of objects, bearing a certain degree of resemblance to one another, and on that account denominated by a single appellation, which may be applied to express any one of them.
When the greater part of objects had thus been arranged under their proper classes and assortments, distinguished by such general names, it was impossible that the greater part of that almost infinite number of individuals, comprehended under each particular assortment or species, could have any peculiar or proper names of their own, distinct from the general name of the species. When there was occasion, therefore, to mention any particular object, it often became necessary to distinguish it from the other objects comprehended under the same general name, either, first, by its peculiar qualities; or, secondly, by the peculiar relation which it stood in to some other things. Hence the necessary origin of two other sets of words, of which the one should express quality; the other, relation.
Nouns adjective are the words which express quality considered as qualifying, or, as the schoolmen say, in concrete with, some particular subject. Thus the word green expresses a certain quality considered as qualifying, or as in concrete with, the particular subject to which it may be applied. Words of this kind, it is evident, may serve to distinguish particular objects from others comprehended under the same general appellation. The words green tree, for example, might serve to distinguish a particular tree from others