At first glance, only one detail might strike us: if the capitalists themselves have set in motion all the money which circulates in society, they must also advance the money needed for the realisation of their own surplus value. Thus it seems that the capitalists as a class ought to buy their own surplus value with their own money. As the capitalist class has possession of this money resulting from previous periods of production, even prior to the realisation of the product of each working period, the appropriation of surplus value at first sight does not seem to be based upon the unpaid labour of the wage labourer--as it in fact is--but merely the result of an exchange of commodities against an equivalent quantity of money both supplied by the capitalist class itself. A little reflection, however, dispels this illusion. After the general completion of circulation, the capitalists, now as before, possess their money funds which either reverted to them or remained in their hands. Further, they acquired consumer goods for the same amount which they have consumed. (Note that we are still confining ourselves to simple reproduction as the prime condition of our diagram of reproduction: the renewal of production on the old scale and the use of all surplus value produced for the personal consumption of the capitalist class.) Moreover, the illusion vanishes completely if we do not confine ourselves to one period of production but observe a number of successive periods in their mutual interconnections. The value the capitalist puts into circulation to-day in the form of money for the purpose of realising his own surplus value, is in fact nothing but his surplus value resulting from the preceding period of production in form of money. The capitalist must advance money out of his own pocket in order to buy his goods for consumption. On the one hand, the surplus value which he produces each year either exists in a natural form which renders it unfit for consumption, or, if it takes a consumable form, it is temporarily in the hands of another person. On the other hand, he (the capitalist) has regained possession of the money, and he is now making his advances by realising his surplus value from the preceding period. As soon as he has realised his new surplus value, which is still embodied in the commodity-form, this money will return to him. Consequently, in the course of several periods of production, the capitalist class draws its consumer goods from the pool, as well as the other natural forms of its capital. The quantity of money originally in its possession, however, remains unaffected by this process.