In the context of the capital social relation, C-M-C describes the characteristic participation of the working class in circulation, while M-C-M describes the characteristic participation of the capitalist in circulation. One begins the circuit C-M-C just in case he needs or wants something he does not already have. In a society in which all the products of labor appear as commodities, the majority of people begin from a position in which they do not have what they need. Therefore, they have to exchange what they have—their labor-power—for money, and with that money they thereby gain access to social wealth. M-C-M is the characteristic mode of participation of the capitalist in circulation. He is already in possession of enough money to purchase labor-power and constant capital. He then uses these to create more commodities which he then sells for a profit.
This is not to say that the capitalist never participates in the circuit C-M-C. On the contrary, the division of labor ensures that no one is in control of the entire means of production of all commodities. Even the capitalist must use some of his profit to procure his means of existence, although this is ridiculously easier for him than for the vast majority of humankind. But M-C-M is the circuit in which the capitalist participates insofar as he is a capitalist, that is, insofar as he imposes the commodity-form on labor. He may comport himself toward people in other ways, but he does not do so qua capitalist. It is for this reason that Marx calls M-C-M the “general formula of capital”. It is capital’s most primitive and general description.
Neither is this to say that the working class never participates in M-C-M. A working couple may purchase a house in order to provide themselves and their children a home. This is an example of C-M-C in which one works for money in order to use that money to buy something useful (a home). But they may also “invest” in the home in the hopes of selling it for more money in coming years. This is a form of M-C-M. Yet just as C-M-C was a process favoring the capitalist when he participated in it owing to his immense wealth, so is M-C-M a process disfavoring the working class when they participate in it. This is clear in the case of the current housing market collapse—a “crisis” disproportionately deeper and further reaching for the working class than for the capitalist class.
The two classes in the capital social relation each relate to money in their own characteristic ways, and this is also reflected in their characteristic processes of circulation. Insofar as money determines a person’s access to social wealth under the capitalist mode of production, workers fight for increases in wages (amongst other things). They want a greater share of social wealth in exchange for less work. They want to spend more time enjoying life and enriching themselves and less time serving another person. In the circuit C-M-C, M is a barrier between the working class and the fulfillment of its needs and wants. The lower that barrier, the more wealth accrues to the working class. The higher that barrier, the more wealth accrues to capital.
The capitalist by contrast pursues the circuit M-C-M’. In this circuit, C consists in (amongst other things) the labor-power the working class sells to him. The more effectively he imposes the commodity-form on labor, the greater the difference between M and M’. This means getting workers to spend more time working and to spend less time enjoying themselves. Whereas time spent working is dead time to the working class, it is living time to the capitalist. And time the working class spends enriching itself and not producing for the capitalist is dead time the capitalist wishes to eliminate. Therefore, M + ΔM is not only an increase in the capitalist’s wealth; it is also an increase in capital’s ability to impose the commodity-form on labor and to continue the general condition of forced work. The two circuits feed into and contradict one another. This contradiction is equivalent to the class struggle between worker and capitalist.
Next: the different roles of money and commodities in the two circuits