Iván Szelényi, teaching Yale's Foundations of Modern Social Theory (SOCY 151), examines Marx's Grundrisse, written between The German Ideology and Das Kapital. He traces how Marx's earlier account, a uni-linear rise in the division of labor and class struggle driving successive modes of production from slavery through feudalism to capitalism and Communism, gets revised. In the Grundrisse, Marx shifts focus to property relations and ownership, and sketches a more multi-linear picture of historical development rather than a single fixed sequence. The lecture moves chapter by chapter through the major themes of the Grundrisse, the centrality of the division of labor in the earlier German Ideology, the concept of modes of production, and the new, less commonly remembered contributions Marx makes regarding multiple historical trajectories. The aim is to show why this less-known facet of Marx is necessary for a full understanding of his theory of history.