LIFE, ARTIFICIAL LIFE, AND SCIENTIFIC EXPLANATION

Recently, biologists and computer scientists who advocate the ''strong thesis of artificial life'' have argued that the distinction between life and nonlife is important and that certain computer software entit ies could be alive in the same sense as biological entities. These arg uments have been challenged by Sober (1991). I address some of the que stions about the rational reconstruction of biology that are suggested by these arguments: What is the relation between life and the ''signs of life''? What work (if any) might the concept of ''life'' (over and above the ''signs of life'') perform in biology? What turns on scient ific disputes over the utility of this concept? To defend my answers t o these questions, I compare ''life'' to certain other concepts used i n science, and I examine historical episodes in which an entity's vita lity was invoked to explain certain phenomena. I try to understand how these explanations could be illuminating even though they are not acc ompanied by any reductive definition of ''life.''