_The Foregoing Truths Universal._--All the general facts which have been thus far stated hold true wherever wealth is produced. They do not presuppose the facts of a division of labor and a system of exchanges, and they do not even require that there should be any social organization. Men in the most primitive tribes and even men living in Crusoe-like isolation would create wealth by labor aided by capital. The essence of that wealth would be effective utility, and the measure of this, which is value, would be made in the specific way that we have described. The varieties of capital, the distinction between capital and capital goods, and the law of diminishing productivity of such goods would appear in the most primitive economics as well as in the most advanced. These are by no means all of the facts and principles which are thus of universal application. They are merely a few of the more important and may serve as a foundation or a "Grundlegung," for further study. If we should extend our list of general and basic truths, it would quickly appear that the incomes that have been treated as rent and the various surplus gains which are analogous to rent are universal economic phenomena which it would be not illogical to discuss in the preliminary part of this treatise. What has been stated, however, concerning the laws of diminishing productivity of successive units of producers' wealth, concerning the diminishing utility of successive units of consumers' wealth, and also concerning the increasing burdensomeness of continuous hours of labor, presents the essential principles on which all rents and quasi-rents rest. It is best to study the applications of these principles as they are made in a civilized state.