Pluralist argues that power is fragmented and fluid, shifting between different coalitions on different issues. No single power elite controls the system. Marxist/Elitist argues that an educated upper-class elite controls groups through resources and communication, and the political system favors middle- and upper-class interests. Social capital and civil society theorists argue that voluntary organizations build social networks and trust that encourage civic engagement and democratic skills, but some organizations may generate "bad" social capital. Criticisms note vague definitions of social capital and little evidence organizations strongly influence politics.