These three laws are the cornerstone of economic theory. They are the framework into which all analysis of special, detailed problems must be fitted. Their scope is very wide. I have purposely refrained from introducing into my statement of them any reference to commodities; for they extend far beyond commodities. Subject to an important qualification, they apply to capital, the price paid for the use of capital being what we call the rate of interest. They apply hardly less to "services," to the remuneration of labor of every kind and grade. People sometimes protest warmly against the idea of treating labor "like a commodity." If this indignation expresses no more than a belief that in matters concerning conditions of work, and relations between employees and the management, the sensibilities of human nature should be taken into due account, it is based on elementary decency and commonsense. But if, as sometimes appears, it is directed against the fact that the remuneration of labor is controlled by the laws of supply and demand, it is a mere baying at the moon, with singularly little provocation. For these laws are in no way peculiar to commodities, and it is no one's fault that they include commodities too within their scope. But let us go back to the laws themselves, and probe them and dissect them, and turn them this way and that, so that we may perceive their full content, and grasp it firmly in our minds. The third law implies a prevailing tendency for demand to be equal to supply. This tendency, as was suggested in Chapter I, can be verified by anyone from his experience and observation (provided he is a reasonable person, and not the tiresome kind who would dispute the law of gravitation because he sees that a feather falls to the ground more slowly than a stone). But it can also be deduced as a corollary from the two preceding laws; and to regard it in this way will help us to appreciate its significance. Start, for instance, by supposing that demand is in excess of supply. Then the price will tend to rise. After the price has risen, the supply will become larger, while the demand will fall away. The excess of demand with which we started will thus clearly be diminished. But if there remains any portion of this excess, the same reactions will continue; the price will rise further, and for the same reason; demand will be further checked and supply further stimulated. In other words, these forces must persist until the entire excess of demand over supply is eliminated. If we start by supposing supply to exceed demand, the converse chain of sequences will operate. Now these very simple steps of reasoning illuminate the nature of the normal equilibrium of demand and supply. They reveal that the equilibrium is established and maintained by the agency of _changes in price_, and they enable us to lay it down as perhaps the most important thing that can be said about the price of anything that