For Part 6, Marx begins by again approaching The Labor Theory of Value, specifically the question of what determines the price of labor, which comes in the form of wages. For Marx, it is the amount of time it takes a worker to produce a commodity that determines the value of a commodity. Labor itself is “the immanent measure of value, but it has no value itself” (677). This is why Marx challenges the classical economists’ idea that labor does have a value that its price can be determined from. What is being sold is not the act of working itself— labor—but labor power, which is the ability to do work. The distinction matters because “the capitalist always makes labour-power work longer than is necessary for the reproduction of its own value” (679). The value of this labor power is what determines a worker’s wages.

Drawing on The Relationship Between Base Structure and Superstructure, Marx reiterates that this system is different from historical modes of production. In the past, feudalism still had a distinction between the labor workers did for their own subsistence and the labor they did for their overlords. Both the slave and capitalist modes of production, however, do not make this distinction.