General Systems Theory
Contemporary GST begins with Jay Forrester and The Club of Rome, although it grew out of operations research, used in maritime engineering especially. Using computers to simulate real world systems, incorporating as many relevant factors as the system architects might manage, remains a knowledge worker skill to this day.
The discovery of "chaos" in a more formal mathematical sense, making "seeing into the future" more problematic than in the old determinism of Laplace, gave rise to terms such as "butterfly effect" and "fractional dimension" (fractal). Catastrophe Theory was a precursor as well. Cellular automata studies, including Wolfram's new kind of science, with the computer itself serving as a kind of laboratory, have further advanced our theories about modeling.
Competition for Economics
Given Economics typically features exhibits regarding the inefficiency of monopolies, it stands to reason that the discipline of Economics should not itself go unpaired with at least one competitor (the more the merrier). GST enters the ring as a champion contender, equally if not more capable of providing coherent analysis, forecasting and policy-guiding modeling.
Integral to each of the above chapters is this emphasis on feedback, steering in response to reality checks. Modern computing, in becoming both object oriented, test and event driven, is better able to keep up with our modeling needs than some of the pre-modern, more static approaches.
GST has also been cited in The Washington Post as a controversial set of programs perhaps spelled out in more detail elsewhere on the Web.