Constant capital, the fixed capital of Adam Smith, is thus put on the same level as money and does not enter into the total produce of society, its gross revenue. It does not exist within this total product as an element of value. You cannot get blood out of a stone, and so circulation, the mutual exchange of the total product constituted in this manner, can only lead to realisation of the wages (_v_) and of the surplus value (_s_). However, as it cannot by any means replace the constant capital, continued reproduction evidently must become impossible. Smith indeed knew quite well, and did not dream of denying, that every individual capitalist requires constant capital in addition to his wages fund, his variable capital, in order to run his enterprise. Yet the above analysis of commodity prices, when it comes to take note of capitalist production as a whole, allows constant capital to disappear without a trace in a puzzling way. Thus the problem of the reproduction of capital is completely muddled up. It is plain that if the most elementary premise of the problem, the demonstration of social capital as a whole, were on the rocks, the whole analysis was bound to fail. Ricardo, Say, Sismondi and others took up this erroneous theory of Adam Smith, and they all stumbled in their observations on the problem of reproduction over this most elementary difficulty: the demonstration of social capital. Another difficulty is mixed up with the foregoing from the very outset of scientific analysis. What is the nature of the total capital of a society? As regards the individual producer, the position is clear: his capital consists of the expenses of his enterprise. Assuming capitalist methods of production, the value of his product yields him a surplus over and above his expenses, that surplus value which does not replace his capital but constitutes his net income, which he can consume completely without encroaching upon his capital and which is thus his fund of consumption. It is true that the capitalist may save part of this net income, not consuming it himself but adding it to his capital. But that is another matter, a new step, the formation of a new capital which again must be replaced by subsequent reproduction and must again yield him a surplus. In any case, the capital of an individual always consists of what he requires for production, together with his advances on the running of his enterprise, and his income is what he himself actually consumes or may consume, his fund of consumption. If we ask a capitalist: 'What are the wages you pay your workers?' his answer will be: 'They are obviously part of my working capital.' But if we ask: 'What are these wages for the workers who have received them?'--it is impossible that he should describe them as capital, for wages received are not capital for the workers but income, their fund of consumption.