These observations show that the problem of the reproduction of total capital is not so crude as it often appears to those who approach it merely from the point of view of crises. The central problem might be formulated as follows: how is it possible that, in an unplanned economy, the aggregate production of innumerable individual capitalists can satisfy all the needs of society? One answer that suggests itself points to the continual fluctuations in the level of production in accordance with the fluctuating demand, i.e. the periodical changes in the market. This point of view, which regards the aggregate product of society as an undifferentiated mass of commodities, and treats social demand in an equally absurd way, overlooks the most important element, the _differentia specifica_ of the capitalist mode of production. We have seen that the problem of capitalist reproduction contains quite a number of precisely defined relations referring to specific capitalist categories and also, _mutatis mutandis_, to the general categories of human labour. The real problem consists in their inherent tendencies towards both conflict and harmony. Marx's diagram is the scientific formulation of the problem. Inquiry must now be made into the implications of this diagram analytic of the process of production. Has it any real bearing on the problems of actual life? According to the diagram, circulation absorbs the entire social product; all consumers' needs are satisfied, and reproduction takes place without friction. The circulation of money succeeds the circulation of commodities, completing the cycle of social capital. But what is the position in real life? The relations outlined in the diagram lay down a precise first principle for the division of social labour in a planned production--always providing a system of simple reproduction, i.e. no changes in the volume of production. But no such planned organisation of the total process exists in a capitalist economy, and things do not run smoothly, along a mathematical formula, as suggested by the diagram. On the contrary, the course of reproduction shows continual deviations from the proportions of the diagram which become manifest (_a_) in the fluctuations of prices from day to day; (_b_) in the continual fluctuations of profits; (_c_) in the ceaseless flow of capital from one branch of production to another, and finally in the periodical and cyclical swings of reproduction between over-production and crisis. And yet, apart from all these deviations, the diagram presents a socially necessary average level in which all these movements must centre, to which they are always striving to return, once they have left it. That is why the fluctuating movements of the individual capitalists do not degenerate into chaos but are reduced to a certain order which ensures the prolonged existence of society in spite of its lack of a plan.