This theory provides a way of thinking about the planning of health promotion interventions that places a spotlight on the relationship between environmental and behavioural determinants of health. This relationship is reciprocal; the environment affects health-related behaviours, and people can, through their actions, affect the environment.

This approach assumes that our health is shaped by many environmental subsystems, including our family, community, workplace, cultural beliefs and traditions, economics, the physical world, and our web of social relationships. Health promotion efforst must thus be comprehensive, addressing those systems that adversely affect the person's capacity for living healthily.

People should be expected to behave differently in different environments. An individual's behavioural predispositions may vary with situation because the situation is partially responsible for those predispositions. In addition, people have different capacities for action in varying environments because environments differ in the resources they provide to individuals. Furthermore, the reinforcements we receive for a particular action may be quite different across contexts - even potentially being positive in one environment and negative in another.