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.

nonlinear interactions almost always make the behavior of the aggregate more complicated than would be predicted by summing or averaging.

Particular individuals do not recur, but their building blocks do.

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

Model building is the art of selecting those aspects of a process that are relevant to the question being asked. As with any art, this selection is guided by taste, elegance, and metaphor; it is a matter of induction, rather than deduction. High science depends on this art.

The recycling of resource by the aggregate behavior of a diverse array of agents is much more than the sum of the individual actions.

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