Precisely what is rendered, then, in all cases of Personal Services in each of their three loose kinds, is _muscular motion conjoined with mental effort and both these assisted by habit and by some form of what we call Capital_. The Services are therefore _Personal_ in the highest sense. The Mind and Body of the Laborer conspire to render them. The most sagacious animal can never be trained to render one of them. They are wholly _human_. Nevertheless the muscular part in the rendering--motion and resistance to motion--is just what tools and machinery can be made to take the place of in large measure but never in whole measure, because tools may not be taught _to think_. It may seem sometimes as if machinery were about to take the place of human hands in some classes of Production; but it will be found in the ultimate issue, as it has been found in every stage of the process, that human hands and human minds in action are absolutely essential at every point of the Exchanges among men. Men are so made and Society is so organized, that they need increasingly for their comfort and progress the personal services of their fellow-men, and can render their own in exchange for these; and consequently, there never can fail (under freedom) a MARKET for Personal Services of the three kinds. Having now seen as closely as possible what that is which is rendered in personal services, let us pass to the principles which determine their remuneration. That is, we will now inquire carefully into the Value of personal services. We have learned already, that Demand and Supply in their action and reaction upon each other determine in all cases the value of Commodities for the time being; and we shall find it to be equally the dictate of all reason, and the outcome of all experience, that Demand and Supply decide too in all cases on the value of all Services and all Credits then and there. Shall we look first at the considerations that issue in the Demand for personal services, and then at those other considerations that limit the Supply of them? 1. Demand is never the mere desire for anything, but desire coupled with the ability to pay for it at rates satisfactory to the present holder. The Demand for Services, therefore, is made by the prospective purchasers of them; and the purchasers, of course, are those who desire them and are willing to pay for them at current rates. It will be easiest and surest for us to study the Demand for Services in each of the three classes of them in succession.