  The standard assumptions that underlie many conceptual and quantitative
frameworks do not hold for many complex physical, biological, and social
systems. Complex systems science clarifies when and why such assumptions fail
and provides alternative frameworks for understanding the properties of complex
systems. This review introduces some of the basic principles of complex systems
science, including complexity profiles, the tradeoff between efficiency and
adaptability, the necessity of matching the complexity of systems to that of
their environments, multi-scale analysis, and evolutionary processes. Our focus
is on the general properties of systems as opposed to the modeling of specific
dynamics; rather than provide a comprehensive review, we pedagogically describe
a conceptual and analytic approach for understanding and interacting with the
complex systems of our world. With the exception of a few footnotes, this paper
assumes only a high school mathematical and scientific background, so that it
may be accessible to academics in all fields, decision-makers in industry,
government, and philanthropy, and anyone who is interested in systems and
society.
