as capital, labour presupposes capital, and capital presupposes labour. Money is not in any way something trans-historical or "natural" (which goes for the other categories of the economy as well), and gains its value due to social relations rather than any inherent quality. The individual doesn't exist in some form of vacuum but is rather enmeshed in social relations. For Marx, the capitalist stage of development or "bourgeois society" represented the most advanced form of social organization to date, but he also thought that the working classes would come to power in a worldwide socialist or communist transformation of human society as the end of the series of first aristocratic, then capitalist and finally working class rule was reached. Following Adam Smith, Marx distinguished the use value of commodities from their exchange value in the market. According to Marx, capital is created with the purchase of commodities for the purpose of creating new commodities with an exchange value higher than the sum of the original purchases. For Marx, the use of labor power had itself become a commodity under capitalism because the exchange value of labor power—as reflected in the wage—is less than the value it produces for the capitalist. He argues this difference in values constitutes surplus value, which the capitalists extract and accumulate. In his book Capital, Marx argues that the capitalist mode of production is distinguished by how the owners of capital extract this surplus from workers—all prior class societies had extracted surplus labor, but capitalism was new in doing so via the sale-value of produced commodities. He argues that a core requirement of a capitalist society is that a large portion of the population must not possess sources of self-sustenance that would allow them to be independent and must instead be compelled to survive to sell their labor to manage to survive. In conjunction with his criticism of capitalism was Marx's belief that exploited labor would be the driving force behind a revolution . For Marx, this cycle of the extraction of the surplus value by the owners of capital or the bourgeoisie becomes the basis of class struggle. In Imperialism, the Highest Stage of Capitalism (1916), Vladimir Lenin modified classic Marxist theory and argued that capitalism necessarily induced monopoly capitalism—which he also called "imperialism"—to find new markets and resources, representing the last and highest stage of capitalism. Some 20th-century Marxian economists consider capitalism to be