Final answer:
Karl Marx believed that capitalism would eventually collapse and be replaced by socialism and, ultimately, communism, as he detailed in his works with Friedrich Engels.
Step-by-step explanation:
The thinker who believed capitalism would ultimately collapse upon itself and that socialism was the pathway towards a prosperous society was Karl Marx. Marx, along with his collaborator Friedrich Engels, developed a comprehensive theory on the dynamics of societal structures and economies, known as Marxism. Marx viewed the history of society as a history of class struggles and predicted that the conflicts between the bourgeoisie, who owned the means of production, and the proletariat, who were the workers, would lead to the fall of capitalism and the rise of socialism and eventually communism. This revolutionary thought process was detailed in the influential works authored by Marx and Engels, such as the Communist Manifesto published in 1848. Their ideas remain a significant part of the discourse on economic systems and social theory.