Nearly a century and a half after he died in 1883, the German philosopher Karl Max remains one of the best-known and controversial thinkers of the modern world. For many on the left of the political spectrum, he is the preeminent theorist of modern capitalism, a pioneering figure who predicted many of the problems of life under industrial capitalism and identified the need for radical changes to underlying economic structures. For others who know him mainly as the leading voice of communism, he is associated with (if not responsible for) the many atrocities committed throughout the 20th century under communist regimes. Regardless of whether one admires or despises him, Marx changed philosophy by offering an intellectually rich analysis of capitalism and fusing it with a program of political revolution. Throughout his career, he carried on the tradition of German philosophical idealism by seeking to trace the movement of history toward some kind of rational conclusion. But unlike his predecessors such as Kant and Hegel, Marx directly participated in political movements he believed were helping to bring history toward that conclusion.

Marx viewed history as the struggle between rival economic classes. With the advent of industrial capitalism, which was rapidly transforming the world into its own image, all of humanity would eventually fall into one of two classes: the bourgeoisie (that is, the owners of the means of production), or the proletariat, meaning wage laborers.