The immune system is a network of cells that recognize and attack foreign invaders. The system asks one profound question: What is self, and what is not self?.... The community needs an immune response, to determine what is self and not self. The community needs to ask, for instance, if a certain action continues, whether it will enhance the mission of the congregation or detract from it. Does an individual's or a group's behavior contradict or serve the congregation's purpose? Is there clarity about who is responsible for what and accountable to whom?

- Peter Steinke, Healthy Congregations: A Systems Approach (Alban Institute, 2006), p. 91.