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

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.

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.

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

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

The measure of performance of any given agent is the amount of money it accumulates through its actions.

Unwrapping occurs when the "solution" is explicitly built into the program from the start.