But, on this simple and, to a certain extent, measurable basis of necessary, universal, and limited wants, we rear a superstructure of other kinds of want. Of the distinctively human wants, there are many that become “necessary” from the individual or social development of intellectual and spiritual beings. Beyond these, again, there are innumerable desires, caprices, and follies. These, however, are not in the least limited in their demands: here “the appetite grows by what it feeds on.” As civilisation and as wealth progress, not only does the old circle of want expand, but new wants awaken. This makes classification of such wants all but impossible. Between the wants of the savage or the child and those of the educated man or delicately nurtured woman, there is a long gradation of almost infinite fineness. How are we to put in one category the hunger and thirst which are satisfied, among members of one class, by bacon and beer, and, among members of another class, by stately dinners and rare vintages; or the “love of dress,” which in one sphere demands “a black silk and a gold brooch,” in another, diamonds and old lace? Yet the fact that goods may be purchased at prices from a farthing upwards, proves that the community _has_ classified its wants in some sort of way. We find exchange existing in all communities, even the simplest, and exchange presupposes that we have already arranged our wants on a scale, and said that the satisfaction of such and such wants confers a high value on the goods which satisfy them, and the satisfaction of such and such a low value. What is the principle of this scale? Adam Smith, and all who have followed him in paraphrasing his text “a diamond has scarce any value in use,” certainly referred to a scale of wants, and considered this scale so important, and so universally recognised, that they had to separate off the value measured by it (use value) from the value measured by money or barter (exchange value). But they did so instinctively, and, if we inquire what this scale is, we have some difficulty in translating the instinctive expression.