The world is a complex, interconnected, finite, ecological - social - psychological - economic system. We treat it as if it were not, as if it were divisible, separable, simple, and infinite. Our persistent, intractable global problems arise directly from this mismatch.

A system is a set of things people, cells, molecules, or whatever interconnected in such a way that they produce their own pattern of behavior over time... The system, to a large extent, causes its own behavior.

Glaciers are almost gone from Glacier National Park

Since the Earth is finite, and we will have to stop expanding sometime, should we do it before or after nature's diversity is gone?

How do we appreciate the good without letting it be the enemy of the perfect? How do we keep a step in the right direction from becoming a stopping point? How do we get beyond shades of insipid light green?

There are no separate systems. The world is a continuum. Where to draw a boundary around a system depends on the purpose of the discussion.

Mesarovic and Pestel are critical of the Forrester-Meadows world view, which is that of a homogeneous system with a fully predetermined evolution in time once the initial conditions are specified.