And about the consumers of interest and ground rent as buyers, Marx says: 'Now, if that portion of the surplus-value of commodities, which the industrial capitalist yields in the form of ground rent or interest to other shareholders in the surplus-value, cannot be in the long run converted into money by the sale of the commodities, then there is an end to the payment of rent and interest, and the landowners or recipients of interest can no longer serve in the role of miraculous interlopers, who convert aliquot portions of the annual reproduction into money by spending their revenue. The same is true of the expenditure of all so-called unproductive labourers, State officials, physicians, lawyers, etc., and others who serve economists as an excuse for explaining inexplicable things, in the role of the 'general public'.[108] Seeing that we cannot discover within capitalist society any buyers whatever for the commodities in which the accumulated part of the surplus value is embodied, only one thing is left: foreign trade. But there are a great many objections to a method that conceives of foreign trade as a convenient dumping ground for commodities which cannot be found any proper place in the reproductive process. Recourse to foreign trade really begs the question: the difficulties implicit in the analysis are simply shifted--quite unresolved--from one country to another. Yet if the analysis of the reproductive process actually intends not any single capitalist country but the capitalist world market, there can be no foreign trade: all countries are 'home'. This point is made by Marx already in the first volume of _Capital_, in connection with accumulation: 'We here take no account of export trade, by means of which a nation can change articles of luxury either into means of production or means of subsistence, and _vice versa_. In order to examine the object of our investigation in its integrity, free from all disturbing subsidiary circumstances, we must treat the whole world as one nation and assume that capitalist production is everywhere established and has possessed itself of every branch of industry.'[109] The same difficulty presents itself if we consider the matter from yet another aspect. In Marx's diagram of accumulation we assumed that the portion of the social surplus value intended for accumulation exists from the first in a natural form which demands it to be used for capitalisation. 'In one word, surplus-value is convertible into capital solely because the surplus-product, whose value it is, already comprises the material elements of new capital.'[110] In the figures of our diagram: I. _5,000c + 1,000v + 1,000s = 7,000_ means of production II. _1,430c + 285v + 285s = 2,000_ means of consumption