For labor-power $1000 For materials 1000 For repairs and replacement of machinery 100 ----- He receives, for the gross product 3100 $2100 The surplus-value is, therefore 1000 and this sum is the fund from which rent, interests, and profits must be paid. It will be observed that there is no moral condemnation of the capitalist involved in this illustration. He simply buys the commodity, labor-power, at its full market price, as in the case of all other commodities. No ethical argument enters into it at all. It is very evident, however, that the interest of the capitalist will be to get as much surplus-value as possible, by buying labor-power at the lowest price possible, prolonging the working day, and intensifying the productivity of the labor-power he buys, while the interest of the workman will be equally against these things. Here we have the cause of class antagonism--not in the speeches of agitators, but in the facts of industrial life. This is the Marxian theory of surplus-value in a nutshell. Rent, interest, and profit, the three great divisions of capitalist income into which this surplus-value is divided, are thus traced to the exploitation of labor, resting fundamentally upon the ownership by the exploiting class of the means of production. Other economists, both before and since Marx, have tried to explain the source of capitalist income in very different ways. An early theory was that profit originates in exchange, through "buying cheap and selling dear." That this is so in the case of individual traders is obvious. If A sells to B commodities above their value, or buys commodities from him below their value, it is plain that he gains by it. But it is equally plain that B loses. If one group of capitalists gains what another group loses, the gains and losses balance each other; there is no gain to the capitalist class as a whole. Yet that is precisely what occurs--the capitalist class as a whole does gain, and gain enormously, despite the losses of individual members of that class. It is that gain to the great body of capitalists, that general increase in their wealth, which must be accounted for, and which exchange cannot explain. Only when we think of the capitalist class buying labor-power from outside its own ranks, generally at its natural value, and using it, is the problem solved. The commodity which the capitalist buys creates a value greater than its own in being used up.