Karl Marx's contributions significantly influenced the development of socialist thought through his critique of capitalism and focus on class struggle. His seminal work, "The Communist Manifesto," laid out his theories on class relations and the socio-economic conflicts between the bourgeoisie and proletariat. Marx argued that capitalist societies inherently create inequality, advocating for a classless society. His ideas inspired various political movements and revolutions, reshaping global views on economics, social justice, and the nature of work.