Ludwig Andreas von Feuerbach was a German anthropologist and philosopher, best known for his book The Essence of Christianity, which provided a critique of Christianity that strongly influenced generations of later thinkers, including Charles Darwin, Karl Marx, Sigmund Freud, Friedrich Engels, Mikhail Bakunin, Richard Wagner, and Friedrich Nietzsche.

Karl Marx was a German-born philosopher, economist, political theorist, historian, sociologist, journalist, and revolutionary socialist. His best-known works are the 1848 pamphlet The Communist Manifesto and the three-volume Das Kapital (1867–1894); the latter employs his critical approach of historical materialism in an analysis of capitalism and is the culmination of his intellectual efforts. Marx's ideas and theories and their subsequent development, collectively known as Marxism, have exerted enormous influence on modern intellectual, economic and political history.