Review of Video #6 of Crash Course Sociology.
Marx was concerned with the question: how could people be free? This led to Marx developing a model of history as a matter of struggling classes, each aligned with either the forces or relations of production. Modes of production, composed of forces and relations of production, develop together until they eventually come into conflict, leading to a revolution of the oppressed class and the institution of a totally new set of relations, where the workers benefit from the efforts of their labour.
To Marx, the economy (i.e. the organisation of labour and resources) was the foundation of society, with everything else the superstructure. Humans must cooperate around labour in order to free ourselves from natural constraints, thus entangling ourselves in social constraints. Thus the organistion of labour (who benefits and how it changes) is central to the question of freedom. This gave rise to the perspective of historical materialism.
In developing this model, Marx laid the foundation for the paradigm of conflict theory in sociology. Marx’s ideas gave rise to a host of conflict theories in sociology.