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 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, or 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 correlative 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 correlative 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 correlative 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, the 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 correlative 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
