It is wrong to speak of labor in so far as it is applied to the production of use-values as of _the only_ source of wealth, namely, the material wealth produced by it. Being an activity intended to adapt materials to this or that purpose, it requires matter as a prerequisite. In different use-values the proportion between labor and raw material varies greatly, but use-value always has a natural substratum. Labor, as an activity, directed to the adaptation of raw material in one form or another, is a natural condition of human existence, a condition of exchange of matter between man and nature, independent of all social forms. On the contrary, labor producing exchange value is a specifically social form of labor. Tailoring, e. g., in its material manifestation as a distinct productive activity, produces a coat, but not the exchange value of the coat. The latter is produced not by the labor of the tailor as such, but by abstract universal labor, and that belongs to a certain organization of society which has not been brought about by the tailor. Thus, the women under the ancient system of house industry made coats without producing the exchange value of the coats. Labor as a source of material wealth was known to Moses, the legislator, as well as to Adam Smith, the customs official.[9] Let us consider now some propositions which follow from the determination of exchange value by labor-time. As a use-value, every commodity owes its usefulness to itself. Wheat, e. g., serves as an article of food. A machine saves labor to a certain extent. This function of a commodity by virtue of which it serves only as use-value, as an article of consumption, may be called its service, the service which it renders as use-value. But as an exchange value, a commodity is always regarded as a result; the question in this case is not as to the service which it renders, but as to the service[10] which it has been rendered in its production. Thus, the exchange value of a machine is determined not by the quantity of labor-time which it saves, but by the quantity of labor-time which has been expended on its own production and which is, therefore, required to produce a new machine of the same kind.