We arrange those ideas, also, in classes; to the end that every name may serve the purpose of marking, as extensively as possible. Thus the term fear is {141} applicable to a state of mind, of which the instances form a class. In like manner, courage is the name of a class; temperance, ignorance, piety, and so on, names of classes. Republic, aristocracy, monarchy, are names, each of them, not of an individual government, a government at one time and place, but of a class, a sort of government, at any time and place. The names of the ideas which are thus mentally clustered, are exempt from that ambiguity which we saw belonged to the names of both classes of sensible ideas. The names of sensible ideas generally stand for the sensations as well as the ideas. The names of the mental ideas are not transferable to sensations. But they are subject to another uncertainty, still more fertile in confusion, and embarrassment. As the combinations are formed arbitrarily, or in other words, as the ideas of which they are composed, are more or less numerous, according to pleasure, and each man of necessity forms his own combination, it very often happens, that one man includes something more or something less than another man in the combination to which they both give the same name. Using the same words, they have not exactly the same ideas. In the term piety, for example, a good catholic includes many things which are not included in it by a good protestant. In the term good manners, an Englishman of the present day does not include the same ideas which were included in it by an Englishman two centuries ago; still less those which are included in it by foreigners of habits and usages dissimilar to our own. Prudence, in the mind of a man of rank and fortune, has a very different meaning from what it bears in the minds of the {142} frugal and industrious poor. Under this uncertainty in language, it not only happens that men are often using the same expressions when they have different ideas; but different, when they have the same ideas.[44]