What is the definition of life? Artificial life environments provide an interesting test case for this classical question. Understanding what such systems can tell us about biological life requires negotiating the tricky conceptual boundary between virtual and real life forms. Drawing from Wittgenstein’s analysis of the concept of a game and a Darwinian insight about classification, I argue that classifying life involves both causal and pragmatic elements. Rather than searching for a single, sharp definition, these considerations suggest that life is (...) a cluster concept with fuzzy boundaries and that there are multiple legitimate ways to make the notion precise for different scientific purposes. This pluralist, realist account avoids unnecessary border disputes by emphasizing how science negotiates such questions in relation to theory and evidence. I also discuss several objections to this approach, including a “moral hesitation” some have to allowing broader application of the concept of life to include artificial life. (shrink)