Karl Marx and Emile Durkheim developed two major sociological theories: conflict theory and functionalism. Conflict theory, developed by Marx, views society as consisting of groups that compete for limited resources, which leads to conflict and struggle between social classes. Functionalism, developed by Durkheim, views society as a system of interconnected parts that work together to maintain stability and social equilibrium. When one part of society changes, other parts must adapt to accommodate the change and restore balance.