The characteristic feature of the _régime_ of capital, or, as Marx usually calls it, the capitalistic method of production, is, that industrial operations are carried on by individual capitalists employing free labourers, whose sole dependence is the wage they receive. Those free labourers perform the function fulfilled in other states of society by the slave and the serf. In the development of the capitalistic system is involved the growth of the two classes,—the capitalist class, enriching itself on the profits of industry, which they control in their own interest, and the class of workers, nominally free, but without land or capital, divorced, therefore, from the means of production, and dependent on their wages—the modern proletariat. The great aim of the capitalist is the increase of wealth through the accumulation of his profits. This accumulation is secured by the appropriation of what the socialists call surplus value. The history of the capitalistic method of production is the history of the appropriation and accumulation of surplus value. To understand the capitalistic system is to understand surplus value. With the analysis of value, therefore, the great work of Marx begins. The wealth of the societies in which the capitalistic method of production prevails appears as an enormous collection of commodities. A commodity is in the first place an external object adapted to satisfy human wants; and this usefulness gives it value in use, makes it a use value. These use values form the material of wealth, whatever its social form may be. In modern societies, where the business of production is carried on to meet the demands of the market, for exchange, these use values appear as exchange values. Exchange value is the proportion in which use values of different kinds exchange for each other. But the enormous mass of things that circulate in the world market exchange for each other in the most different proportion. They must, however, have a common quality, or they could not be compared. This common quality cannot be any of the natural properties of the commodities. In the business of exchange one thing is as good as another, provided you have it in sufficient quantity.