Functionalism and conflict theory are two major perspectives on how society works. The two take very different approaches to understanding what society is like.
Functionalism holds that all parts of a society play a role in keeping society stable and relatively harmonious. To functionalists, even bad things like crime and deviance actually help to keep our society stable. They say that crime and deviance help to ensure that the rest of us (those who do not act in criminal or deviant ways) feel connected to one another. We see people who act in bad ways and we feel that we all have something in common because we follow society’s rules and do not act wrongly. Thus, functionalists believe that even bad aspects of society help to bind us together.
By contrast, conflict theorists believe that all aspects of our society do not create harmony. Instead, the various aspects of our society come about through conflict. Society is not made up of parts that work together to bring stability. Instead, it is made up of parts that compete with each other for dominance. In this view, even things that we might think of as good (family, religion, schools) are actually created by the dominant forces in society as a way to keep the other parts of society down. Families are created by men to dominate women. Religion is created by the powerful to keep the poor and weak from rebelling. Schools are created to teach the values of our society so that even the poor think that we have a great society that is basically fair.
In these ways, functionalism and conflict theory are essentially polar opposites in terms of their views of how the various parts of society interact.