With theory, we can separate fundamental characteristics from fascinating idiosyncrasies and incidental features. Theory supplies landmarks and guideposts, and we begin to know what to observe and where to act.

Looking back to data, we can see if the consequences are plausible; looking forward to theory, we can see if general principles are suggested.

Holland's and Kauffman's work, together with Dawkins' simulations of evolution and Varela's models of autopoietic systems, provide essential inspiration for the new discipline of artificial life, This approach, initiated by Chris Langton (1989, 1992), tries to develop technological systems (computer programs and autonomous robots) that exhibit lifelike properties, such as reproduction, sexuality, swarming, and co-evolution.

This use of building blocks to generate internal models is a pervasive feature of complex adaptive systems.

The multiplier effect is a major feature of networks and flows. It arises regardless of the particular nature of the resource, be it goods, money, or messages.

From the point of view of physics, it is a miracle that [seven million New Yorkers are fed each day] without any control mechanism other than sheer capitalism.

Evolution continually innovates, but at each level it conserves the elements that are recombined to yield the innovations.