Their substance is indestructible. Man can no more destroy an atom of the physical universe than he can create one. His powers in Consumption as in Production are limited to _altering_ Natural Resources in location and form. The essential Economic difference between Production and Consumption is that Production alters natural objects so as to adapt them to the satisfaction of human wants, whereas Consumption alters Artificial Objects in the process of satisfying those wants. Production is the drawing forth by Man of Artificial Objects from and upon Natural Resources; Consumption is the passing back by Man of Artificial Objects to Natural Resources. With the processes of Consumption the science of Economics has nothing to do. Its functions end with delivery to final consumers. Whenever Consumption is declared to be a phase of Economics, thoughtful consideration will ascribe the declaration, not to the processes of Consumption but to the preceding demand for Artificial Objects to consume. The human demand for Artificial Objects to consume is the incentive to the Productive Process. Production, therefore, and demand for Consumption, are Economic correlatives, Production having Consumption for its object, demand for Consumption depending upon Production for satisfaction. Without Production by Man, there could be no Artificial Objects to consume; without Consumption by Man, there would be no incentive to produce. Production must, of course, precede Consumption. No Artificial Object can be consumed before it has been produced. But demand for Consumption as certainly precedes Production. An opposite inference might be drawn from the fact that particular Artificial Objects are often produced in advance of specific demand for them. In fact, however, the output is always in response to demand, either actual or probable--like the outflow from a reservoir of water which follows the inflow but to which there would be no inflow were it not for anticipated demand. Production in advance of actual demand indicates nothing more than that the producers are confident that such demand exists in embryo. If they err, the Products have no market; if they have guessed aright, the volume of Products increases to meet the demand. By and large, then, demand for Consumption regulates Production; or, in Economic phrasing, supply in Production is determined by demand for Consumption. Being continuous, the human demand for Artificial Objects to consume stimulates continuous Production; being progressive, it promotes improvement in Productive methods and accomplishments. I. HUMAN FACTORS The Productive Process is accomplished by Man’s exertions, mental and physical, each of those forms of exertion being dependent upon the other.