• Complex systems have hierarchies of power and control.

• They contain independent agents that interact with other agents are often resistant to top-down control.

• Agents interact with other agents that are above, equal to, or below their position in the hierarchy.

• Knowing the parts of a complex system does not equal understanding the system.

• There are non-linear relationships between efforts to change systems (usually from higher levels in the hierarchy) and the amount of change that actually occurs in the lower levels.

o. A complexity science concept that has moved into popular thought is the tipping point, or the notion that a small change can spread from its own momentum across agents in a system without much external energy spent to drive the change.

• In more resilient complex adaptive systems, the top hierarchies provide information and resources to the lower levels. The agents in the lower levels use these resources that make the most sense in their local environment.

• This top-down/bottom-up information and resource cycle results in emergent properties through a complex system that is unpredictable.

• Complexity principles even apply to an individual human. The human “system” contains many hierarchies that interact from the top-down and bottom-up at the same time. The impact of the external environment on health comes from stress activation, etc., at the lowest level. In clinic, we see the effects of heterogeneity of dynamic interactions within body systems at lower level, and environment elements at the whole person higher levels.