Marx, Karl (1818–83), German philosopher and social and economic theorist, founder of modern socialism. Born in Prussia of Jewish parents, Marx studied philosophy in Bonn and Berlin. When the Cologne newspaper he edited the Rheinische Zeitung, was suppressed (1843), he moved with his wife Jenny von Westphalen to Paris, where he met Friedrich Engels in 1844, and later to London, where he spent most of his life in great poverty.
In 1848 Marx and Engels published the Communist Manifesto, which established the theoretical basis for a socialist movement based on class struggle and sociological analysis rather than moral appeals to natural rights. Marx and Engels later cofounded (1864) International Workingmen's Association, the first international revolutionary organization. Marx wrote prolifically on questions of philosophy, history, and politics, but his greatest work was Capital, his analysis of the system of capitalism. Only the first volume was published in his lifetime (1867). After his death, Engels completed the second (1885) and third (1894) volumes. Building on his criticism of the theories of Adam Smith and David Ricardo, Marx developed the theory of surplus-value to explain the exploitation of workers under capitalism. He predicted that the working class, or proletariat, would grow in numbers and power and would eventually overthrow capitalism, and establish socialism. The economic and political analysis of capitalism was integrated into a broader theory called historical materialism, which analyzed human history in terms of a sequence of kinds of society based on different forms of ownership of the means of production. Marx's influence has been widespread, and he is universally regarded as one of the major thinkers of the 19th century.