As neither quality nor relation can exist in abstract, it is natural to suppose that the words which denote them considered in concrete, the way in which we always see them subsist, would be of much earlier invention than those which express them considered in abstract, the way in which we never see them subsist. The words green and blue would, in all probability, be sooner invented than the words greenness and blueness; the words above and below, than the words superiority and inferiority. To invent words of the latter kind requires a much greater effort of abstraction than to invent those of the former. It is probable therefore, that such abstract terms would be of much later institution. Accordingly, their etymologies generally show that they are so, they being generally derived from others that are concrete.
But though the invention of nouns adjective be much more natural than that of the abstract nouns substantive derived from them, it would still, however, require a considerable degree of abstraction and generalization. Those, for example, who first invented the words green, blue, red, and the other names of colours, must have observed and compared together a great number of objects, must have remarked their resemblances and dissimilitudes in respect of the quality of colour, and must have arranged them, in their own minds, into different classes and assortments, according to those resemblances and dissimilitudes. An adjective is by nature a general, and in some measure an abstract word, and necessarily presupposes the idea of a certain species or assortment of things, to all of which it is equally applicable. The word green could not, as we were supposing might be the case of the word cave, have been originally the name of an individual, and afterwards have become, by what grammarians call an antonomasia, the name of a species. The word green denoting, not the name of a substance, but the peculiar quality of a substance, must from the very first have been a general word, and considered as equally applicable to any other substance possessed of the same quality. The man who first distinguished a particular object by the epithet of green, must have observed other objects that were not green, from which he meant to separate it by this appellation. The institution of this name, therefore, supposes comparison. It likewise supposes some degree of abstraction. The person who first invented this appellation must have distinguished the quality from the object to which it belonged, and must have conceived the object as capable of subsisting without the quality. The invention, therefore, even of the simplest nouns adjective must have required more metaphysics than we are apt to be aware of. The different mental operations, of arrangement or classing, of comparison, and of abstraction, must all have been employed, before even the names of the different colours, the least metaphysical of all nouns adjective, could be instituted. From all which I infer, that when languages were beginning to be formed, nouns adjective would by no means be the words of the earliest invention.
There is nothing expedient for denoting the different qualities of different substance, which as it requires no abstraction, nor any conceived separation of the quality from the subject, seems more natural than the invention of nouns adjective, and which, upon this account, could hardly fail, in the first formation of language, to be thought of before them. This expedient is to make some variation upon the noun substantive itself, according to the different qualities which it is endowed with. Thus in many languages, the qualities both of sex and of the want of sex are expressed by different terminations in the nouns substantive, which denote objects so qualified. In Latin, for example, lupus, lupa; equus, equa; juvencus, juvenca; Julius, Julia; Lucretius, Lucretia, etc., denote the qualities of male and female in the animals and persons to whom such appellations belong, without needing the addition of any adjective for this purpose. On the other hand, the words, forum, pratum, plaustrum, denote by their peculiar termination the total absence of sex in the different substances which they stand for. Both sex, and the want of all sex, being naturally considered as qualities modifying and inseparable from the particular substances to which they belong, it was natural to express them rather by a modification in the noun substantive, than by any general and abstract word expressive of this particular species of quality. The expression bears, it is evident, in this way, a much more exact analogy to the idea or object which it denotes than in the other. The quality appears, in nature, as a modification of the substance, and as it is thus expressed in language, by a modification of the noun substantive, which denotes that substance, the quality and the subject are, in this case, blended together, if I may say so, in the expression, in the same manner as they appear to be in the object and in the idea. Hence the origin of the masculine, feminine, and neutral genders, in all the ancient languages. By means of these, the most important of all distinctions, that of substances into animated and inanimated, and that of animals into male and female, seem to have been sufficiently marked without the assistance of adjectives, or of any general names denoting this most extensive species of qualifications.
There are no more than these three genders
