But to return more particularly to Mr. Mill. After asserting that the supply is the demand, and the demand is the supply, so frequently, that the unwary reader must feel quite at a loss to know which is which, he comes to a distinct conclusion, which is so directly contradicted both by theory and experience, as to show either that his premises must have been false, or that what he calls his indissoluble train of reasoning consists of mere unconnected links. He says, “It is therefore universally true, that as the aggregate demand and aggregate supply of a nation never can be unequal to one another, so there never can be a superabundant supply in particular instances, and hence a fall in exchangeable value below the cost of production, without a corresponding deficiency of supply, and hence a rise in exchangeable value beyond cost of production in other instances. The doctrine of the glut, therefore, seems to be disproved by a chain of reasoning perfectly indissoluble.”[26] While commodities are merely compared with each other, it is unquestionably true that they cannot all fall together, or all rise together. But when they are compared with the costs of production, as they are in the above passage, it is evident that, consistently with the justest theory, they may all fall or rise at the same time. For what are the costs of production? They are either the quantity of _money_ necessary to pay the labour worked up in the commodity, and in the tools and materials consumed in its production, with the ordinary profits upon the advances for the time that they have been advanced; or they are the quantity of labour in kind required to be worked up in the commodity, and in the tools and materials consumed in its production with such an additional quantity as is equivalent to the ordinary profits upon the advances for the time that they have been advanced. Now it surely cannot be denied theoretically, that all commodities produced in this country may fall in comparison with a commodity produced in Mexico. As little can it be denied theoretically that all commodities produced by British labour may fall as compared with that labour, either from an unusually increased supply of such commodities, or a diminution of demand for them. And when, from these theoretical concessions, required by the universally acknowledged laws of demand and supply, we turn to the facts, we see with our own eyes, and learn from authority which there is no reason whatever for doubting, that a very large mass of commodities does at times fall below the costs of production, whether those costs be estimated in money or labour, without the slightest shadow of pretence for saying that any other equally large mass is raised proportionally above the costs of production.