The greater number of such crises are doubtless special; that is, it is only in some branches of trade that supply outweighs demand. Most theorists deny the possibility of a general glut, although many practitioners stubbornly maintain it.[216-1] J. B. Say relies upon the principle that in the sale of products, as contradistinguished from gifts, inheritances, etc., payment can always be made only in other products. If, therefore, in one branch there be so much supplied that the price declines; as a matter of course, the commodity wanted in exchange will command all the more, and, therefore, have a better vent. In the years 1812 and 1813, for instance, it was almost impossible to find a market for dry goods and other similar products. Merchants everywhere complained that nothing could be sold. At the same time, however, corn, meat and colonial products were very dear, and, therefore, paid a large profit to those who supplied them.[216-2] Every producer who wants to sell anything brings a demand into the market exactly corresponding to his supply. (_J. Mill._) Every seller is _ex vi termini_ also a buyer; if, therefore production is doubled, purchasing power is also doubled. (_J. S. Mill._) Supply and demand are in the last analysis, really, only two different sides of one and the same transaction. And as long as we see men badly fed, badly clothed, etc., so long, strictly speaking, shall we be scarcely able to say that too much food or too much clothing has been produced.[216-3] [Footnote 216-1: When those engaged in industrial pursuits speak of a lasting and ever-growing over-production, they have generally no other reason for their complaints than the declining of the rate of interest and of the undertaker's profit which always accompany an advance in civilization. Compare _J. S. Mill_, Principles, III, ch. 14, 4. However, the same author, I, 403, admits the possibility of something similar to a general over-production.] [Footnote 216-2: _Say's_ celebrated Théorie des Débouchés, called by McCulloch his chief merit, Traité, I, ch. 15. At about the same time the same theory was developed by _J. Mill_, Commerce defended, 1808. _Ricardo's_ express adhesion, Principles, ch. 21. Important germs of the theory may be traced much farther back: _Mélon_, Essai politique sur le Commerce, 1734, ch. 2; _Tucker_, On the Naturalization Bill, 13; Sketch of the Advance and Decline of Nations, 1795, 182.] [Footnote 216-3: Precisely the same commercial crisis, that of 1817 seq., which more than anything else led _Sismondi_ to the conclusion that too much had been produced in all branches of trade, may most readily be reduced to _Say's_ theory.