Iván Szelényi, teaching Foundations of Modern Social Theory at Yale, walks through Marx's move from a theory of alienation to a theory of exploitation. Drawing on the Communist Manifesto, the Grundrisse, and Das Kapital, he explains how the capitalist mode of production turns labor power itself into a commodity, with the worker paid enough to reproduce that labor power while the surplus value it generates goes to the owner. Szelényi lays out Marx's claim that capitalism sorts people into two classes, bourgeoisie and proletariat, then tests that model against history, pointing to artisans and agricultural workers who control their own labor and products as evidence the two-class scheme does not hold up empirically. The lecture runs through four chapters, ending with a direct question about how many classes actually exist in capitalist society.