Broken Windows Theory, an academic theory proposed by James Q. Wilson and George Kelling in 1982 that used broken windows as a metaphor for disorder within neighborhoods. Their theory links disorder and incivility within a community to subsequent occurrences of serious crime.

Disorder causes fear that fear causes a breakdown of social controls (sometimes referred to as community cohesion), and that this breakdown of social controls in turn causes crime.

The Tipping Point (by Malcolm Gladwell), Shows how small actions at the right time, in the right place and with the right people can create a ‘tipping point’, the moment when a domino effect is triggered and an epidemic sweeps through the population.