process of circulation as well as of reproduction. Thus the fact is clear and unequivocal--so long as we remain within the bounds of simple reproduction. Here the problem is solved by the premises themselves; in fact, the solution is already anticipated by the very concept of simple reproduction which indeed is based on the entire surplus value being consumed by the capitalist class. This implies that it must also be the latter who buy it, that is to say, individual capitalists must buy it from each other. 'In the present case', Marx says himself, 'we had assumed, that the sum of money which the capitalist throws into circulation until the first surplus-value flows back to him, is exactly equal to the surplus-value which he is going to produce and monetise. This is obviously an arbitrary assumption, so far as, the individual capitalist is concerned. But it must be correct when applied to the entire capitalist class, when simple reproduction is assumed. It expresses the same thing that this assumption does, namely, that the entire surplus-value is consumed unproductively, but it only, not any portion of the original capital stock.'[140] But simple reproduction on a capitalist basis is after all an imaginary quantity in economic theory: no more and no less legitimate, and quite as unavoidable as [sqrt](-1) in mathematics. What is worse, it cannot offer any help at all with the problem of realising the surplus value in real life, i.e. with regard to enlarged reproduction or accumulation. Marx himself says so for a second time in the further development of his analysis. Where does the money for realising the surplus value come from if there is accumulation, i.e. not consumption but capitalisation of part of the surplus value? Marx's first answer is as follows: 'In the first place, the additional money-capital required for the function of the increasing productive capital is supplied by that portion of the realised surplus-value which is thrown into circulation by the capitalists as money-capital, not as the money form of their revenue. The money is already present in the hands of the capitalists. Only its employment is different.'[141]