According to Marxian theory, class conflict arises in capitalist societies due to contradictions between the material interests of the oppressed proletariat—a class of wage labourers employed by the bourgeoisie to produce goods and services—and the bourgeoisie—the ruling class that owns the means of production and extract their wealth through appropriation of the surplus product (profit) produced by the proletariat.
This class struggle that is commonly expressed as the revolt of a society's productive forces against its relations of production, results in a period of short-term crises as the bourgeoisie struggle to manage the intensifying alienation of labor experienced by the proletariat, albeit with varying degrees of class consciousness. This crisis culminates in a proletarian revolution and eventually leads to the establishment of socialism—a socioeconomic system based on social ownership of the means of production, distribution based on one's contribution and production organized directly for use. As the productive forces continued to advance, Marx hypothesized that socialism would ultimately transform into a communist society; a classless, stateless, humane society based on common ownership and the underlying principle: "From each according to his ability, to each according to his needs".
Marxism has developed into many different branches and schools of thought, though now there is no single definitive Marxist theory. Different Marxian schools place a greater emphasis on certain aspects of classical Marxism while rejecting or modifying other aspects. Many schools of thought have sought to combine Marxian concepts and non-Marxian concepts, which has then lead to contradictory conclusions. However, lately there is movement toward the recognition that historical materialism and dialectical materialism remains the fundamental aspect of all Marxist schools of thought, which should result in more agreement between different schools.
Marxism has had a profound and influential impact on global academia and has expanded into many fields such as archaeology, anthropology, media studies, political science, theater, history, sociology, art history and theory, cultural studies, education, economics, ethics, criminology, geography, literary criticism, aesthetics, film theory, critical psychology and philosophy.