Now, if we consider the result of C—M—C, it comes down to mere interchange of matter, C—C. A commodity has been exchanged for a commodity, a use-value for a use-value, and the transformation of the commodity into money, or the commodity in its form of money, serves merely as a means of effecting this interchange of matter. Money thus appears merely as a medium of exchange of commodities; not as a medium of exchange in general, but as a means of exchange in the sphere of circulation, i. e., a medium of circulation.69
We have seen that the process of circulation of commodities comes to a completion in C—C, appearing as mere barter carried on by means of money; further, that C—M—C represents in general not only two isolated processes, but their dynamic union as well; but to draw from that the conclusion that purchase and sale form an indivisible unit, is a mode of thinking the criticism of which belongs to the domain of logic, and not to that of economics. The separation of purchase and sale in the process of exchange destroys all local, primitive, patriarchal and naively genial barriers to interchange of matter in society. It is, moreover, the general form of the separation of the points of coincidence and opposition in this interchange, carrying within it the possibility of commercial crises, because the antagonism of commodity and money is the abstract and general form of all antagonisms with which the capitalistic system of labor is pregnant. Hence, circulation of money is possible without crises, but crises can not occur without money circulation. In other words, where labor based on the system of private exchange has not reached the stage marked by the existence of money, it is less capable of producing those phenomena which presuppose the full development of the capitalistic mode of production. Bearing this in