  Luxemburg’s study of the dynamic structure of capital accumulation begins with a critique of Volume II of Capital.  More specifically, it starts with Marx’s analysis of capitalism as a “closed system” based on a simplified model of relations of production between capitalists and workers, which abstracts from the existence of non-capitalist economies. As Marx had put it in chapter 24 of Capital, “we must treat the whole world of trade as one nation, and assume that capitalist production is established everywhere and has taken possession of every branch of industry” (Marx 1887 [1990: 727]). The problem with this analysis, Luxemburg pointed out, consists in a mistaken understanding of capital accumulation as a mere question of “the sources of money when the real issue is the effective demand, the use made of goods, not the source of money which is paid for them” (Luxemburg 1913 [AK: 128]). The closed-system analysis, she suggested, made it difficult to explain how capital could be reproduced and valorized in a capitalist society based only on the exploitation of workers, and related extraction of surplus value.