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 that were withered or blasted.
Prepositions are the words which express relation considered, in the same manner, in concrete with the co-relative object. Thus the prepositions of, to, for, with, by, above, below, &c. denote some relation subsisting between the objects expressed by the words between which the prepositions are placed; and they denote that this relation is considered in concrete with the co-relative object. Words of this kind serve to distinguish particular objects from others of the same species, when those particular objects cannot be so properly marked out by any peculiar qualities of their own. When we say, the green tree of the meadow, for example, we distinguish a particular tree, not only by the quality which belongs to it, but by the relation which it stands in to another object.
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 another expedient for denoting the different qualities of different substances, 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, &c. 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 in any of the languages with which I am acquainted; that is to say, the formation of nouns substantive, can, by itself, and without the accompaniment of adjectives, express no other qualities but those three above-mentioned, the qualities of male, of female, of neither male nor female. I should not, however, be surprised, if, in other languages with which I am unacquainted, the different formations of nouns substantive should be capable of expressing many other different qualities. The different diminutives of the Italian, and of some other languages, do, in reality, sometimes, express a great variety of different modifications in the substances denoted by those nouns which undergo such variations.
It was impossible, however, that nouns substantive could, without losing altogether their original form, undergo so great a number of variations, as would be sufficient to express that almost infinite variety of qualities, by which it might, upon different occasions, be necessary to specify and distinguish them. Though the different formation of nouns substantive, therefore, might, for some time, forestall the necessity of inventing nouns adjective, it was impossible that this necessity could be forestalled altogether. When nouns adjective came to be invented, it was natural that they should be formed with some similarity to the substantives, to which they were to serve as epithets or qualifications. Men would naturally give them the same terminations with the substantives to which they were first applied, and from that love of similarity of sound, from that delight in the returns of the same syllables, which is in the foundation of analogy in all languages, they would be apt to vary the termination of the same adjective, according as they had occasion to apply it to a masculine, to a feminine, or to a neutral substantive. They would say, magnus lupus, magna lupa, magnum pratum, when they meant to express a great he wolf, a great she wolf, a great meadow.
This variation, in the termination of the noun adjective, according to the gender of the substantive, which takes place in all the ancient languages, seems to have been introduced chiefly for the sake of a certain similarity of sound, of a certain species of rhyme, which is naturally so very agreeable to the human ear. Gender, it is to be observed, cannot properly belong to a noun adjective, the signification of which is always precisely the same, to whatever species of substantives it is applied. When we say, a great man, a great woman, the word great has precisely the same meaning in both cases, and the difference of the sex in the subjects to which it may be applied, makes no sort of difference in its signification. Magnus, magna, magnum, in the same manner, are words which express precisely the same quality, and the change of the termination is accompanied with no sort of variation in the meaning. Sex and gender are qualities which belong to substances, but cannot belong to the qualities of substances. In general, no quality, when considered in concrete, or as qualifying some particular subject, can itself be conceived as the subject of any other quality; though when considered in abstract it may. No adjective therefore can qualify any other adjective. A great good man, means a man who is both great and good. Both the adjectives qualify the substantive; they do not qualify one another. On the other hand, when we say, the great goodness of the man, the word goodness denoting a quality considered in abstract, which may itself be the subject of other qualities, is upon that account capable of being qualified by the word, great.
If the original invention of nouns adjective would be attended with so much difficulty, that of prepositions would be accompanied with yet more. Every preposition, as I have already observed, denotes some relation considered in concrete with the co-relative object. The preposition above, for example, denotes the relation of superiority, not in abstract, as it is expressed by the word superiority, but in concrete with some co-relative object. In this phrase, for example, the tree above the cave, the word above, expresses a certain relation between the tree and the cave, and it expresses this relation in concrete with the co-relative object, the cave. A preposition always requires, in order to complete the sense, some other word to come after it; as may be observed in this particular instance. Now, I say, the original invention of such words would require a yet greater effort of abstraction and generalization, than that of nouns adjective. First of all, a relation is, in itself, a more metaphysical object than a quality. Nobody can be at a loss to explain what is meant by a quality; but few people will find themselves able to express, very distinctly, what is understood by a relation. Qualities are almost always the objects of our external senses; relations never are. No wonder, therefore, that the one set of objects should be so much more comprehensible than the other. Secondly, though prepositions always express the relation which they stand for, in concrete with the co-relative object, they could not have originally been formed without a considerable effort of abstraction. A preposition denotes a relation, and nothing but a relation. But before men could institute a word, which signified a relation, and nothing but a relation, they must have been able, in some measure, to consider this relation abstractedly from the related objects; since the idea of those objects does not, in any respect, enter into the signification of the preposition. The invention of such a word, therefore, must have required a considerable degree of abstraction. Thirdly, a preposition is from its nature a general word, which, from its very first institution, must have been considered as equally applicable to denote any other similar relation. The man who first invented the word above, must not only have distinguished, in some measure, the relation of superiority from the objects which were so related, but he must also have distinguished this relation from other relations, such as, from the relation of inferiority denoted by the word below, from the relation of juxtaposition, expressed by the word beside, and the like. He must have conceived this word, therefore, as expressive of a particular sort or species of relation distinct from every other, which could not be done without a considerable effort of comparison and generalization.