[5] The law of diminishing returns of successive units of _capital goods_ is based on the same principle as the law of diminishing returns of _capital_, but it is not identical with it. We shall see, in due time, how a permanent fund of producers' wealth actually grows and why each new unit, as it adds itself to the fund, creates a smaller income than did its predecessor.
_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.
_Universal Economic Truths independent of the Special Facts of Sociology._--This first division of economic science borrows none of its premises from sociology, for the truths which compose it would abide if there were no society in existence. Basic facts it takes from Physics, Biology, Psychology, Chemistry, etc. Facts concerning man, nature, and the relation between them are material for it, but relations between man and man come into view only in the later divisions. There, indeed, they do come into the very foreground with results which immeasurably enrich the science. What we may call the socialization of the economic process we shall have next before us, and we shall find it full of critical problems involving the future well-being of humanity. Industry is carried on by a social organism in which men are atomic parts and to which nature has given a constitution with laws of action and development. We have first to study the nature of this industrial organism and the mode in which it would act if it were not subject to any constitutional change; and later we must study it in its process of growth. The economic action of a society which is undergoing no organic changes is the subject of Social Economic Statics, while such changes with their causes and effects constitute the subject of the science of Social Economic Dynamics.