
method for generating new variations, and some rules for capitalizing on
adaptive improvements.
Christopher Langton (1988) has defined artificial life as “the study of
man-made systems that exhibit behaviors characteristic of natural living
systems.” In the same paper, he states, “Life is a property of form, not
matter...” If we accept Langton’s premise, then we would have to admit
that the similarity between an artificial-life program and life itself may be
somewhat stronger than the usual kind of analogy. We will avoid declar-
ing that computer programs live, but will note here and in other places
throughout this book that it is unsettlingly difficult ...