Karl Marx was a German philosopher, social and political theorist, economist, journalist, and revolutionary socialist. He developed the theory of historical materialism, analyzing class struggle under capitalism and predicting the system's overthrow by the proletariat in favour of communism. Marx co-authored The Communist Manifesto (1848) with his lifelong friend Friedrich Engels, and undertook a critique of classical political economy in his magnum opus, Das Kapital (1867–1894). Marx's ideas and their subsequent development, collectively known as Marxism, have had enormous influence and have influenced revolutions and uprisings in many countries.