The occasions, however, are perpetual, on which we need marks for sensations, not in clusters, but taken separately. And language is supplied with {136} names of this description. We have the terms, red, green, hot, cold, sweet, bitter, hard, soft, noise, stench, composing in the whole a numerous class. For many sensations, however, we have not names in one word; but make a name out of two or more words: thus, for the sensation of hearing, derived from a trumpet, we have only the name, "sound of a trumpet;" in the same manner, we have "smell of a rose," "taste of an apple," "sight of a tree," "feeling of velvet." Of those names which denote clusters of sensations, it is obvious (but still very necessary) to remark, that some include a greater, some a lesser number of sensations. Thus, stone includes only sensations of touch, and sight. Apple, beside sensations of touch and sight, includes sensations of smell and taste. We not only give names to clusters of sensations, but to clusters of clusters; that is, to a number of minor clusters, united into a greater cluster. Thus we give the name wood to a particular cluster of sensations, the name canvas to another, the name rope to another. To these clusters, and many others, joined together in one great cluster, we give the name ship. To a number of these great clusters united into one, we give the name fleet, and so on. How great a number of clusters are united in the term House? And how many more in the term City? Sensations being infinitely numerous, all cannot receive marks or signs. A selection must be made. Only those which are the most important are named. Names, to be useful, cannot exceed a certain number. They could not otherwise be remembered. It is, therefore, of the greatest importance that each name should accomplish as much as possible. To this end, {137} the greater number of names stand, not for individuals only, but classes. Thus the terms red, sweet, hot, loud, are names, not of one sensation only, but of classes of sensations; that is, every sensation of a particular kind. Thus also the term, rose, is not the name of one single cluster, but of every cluster coming under a certain description. As rose denotes one class, stone denotes another, iron another, ox another, and so on.[42] [Editor's footnote 42: Economy in the use of names is a very small part of the motive leading to the creation of names of classes. If we had a name for every individual object which exists in the universe, and could remember all those names, we should still require names for what those objects or some of them have in common; in other words, we should require classification, and class names. This will be obvious if it is considered that had we no names but names of individuals, we should not have the means of making any affirmation respecting any object; we could not predicate of it any qualities. But of this more largely in a future note.--_Ed._]