• A generalized structure that represents common reoccurring patterns of behavior in a system.
  • There are several archetypes that have been identified.[1]
  • Each archetype can be translated into a simple narrative story about what is happening and why. This story also identifies potential unintended consequences to avoid.

Complex / Complexity

  • There are different meanings for complex depending on the discipline (e.g., biology, economics, social science). For grantmakers and social-sector actors, complex refers to situations that are both:
    • Political — where there are differences of opinion and lack of agreement and
    • Unpredictable — where it isn’t possible to identify cause and effect in advance, variables are interconnected and interdependent, and there is not a linear progression from action to results.


  • Events are the activities, actions and behaviors we experience.
  • They represent a single point in time, yet events can occur simultaneously. They are tangible and observable with a marked start and finish. Some events are repetitive and others are not.
  • Examples include an election, policy change, earthquake, oil spill, birthday or turning on a light switch.


  • A force is the push or pull by which one event or behavior can trigger another. Forces are people, habits, customs, attitudes, emotions, and any other factor that can either drive or resist change.  The term “forces” was coined by Kurt Lewin and is different, but not mutually exclusive from, other systems terms such as “events” and “behaviors.”

Mental Models

  • A mental model is the set of beliefs, values and assumptions that individuals have about a system. An example is “voting is a right for every adult citizen.”

Patterns of System Behavior

  • By looking at many events over time, it is possible to see patterns form. These patterns are called “behaviors” of the system. In this guide, the redundant term “patterns of behaviors/events” is used to distinguish this systems concept from the generic concept of patterns.
  • They are observable and can be seen at different levels of the system. They help us to understand how events relate to other events.
  • Examples include voting trends, rates of change over time and repeated failure to implement policies.


  • The structure of a system is the relationship between patterns of behavior. A system’s structure drives the patterns of behavior and events and, simultaneously, is created by them over time.
  • Structure includes the interrelationships among parts of a system as well as the processes by which the parts interact over time. Structure may or may not be observable.
  • Examples include the flow of resources to the wealthiest and voter disenfranchisement.


  • A system is a set of parts (e.g., issues, people, organizations, policies, norms) that are interconnected, porously bounded, and continually changing over time.


  • This includes events, forces and mental models. It also includes people, organizations, policies, norms, values and all other parts of a system.

[1] While many people have written about and developed archetypes, one source for examples is Peter Senge's The Fifth Discipline: The Art & Practice of the Learning Organization.