mbgreen@cis.upenn.edu: I have seen the claim in several posts that because Life is Turing complete, you can program a "Life Computer" to enumerate all possible configurations. Is this true? --yes. You can program it to do any computation. At all. Andy Latto: When I say that a Life computer could "enumerate all finite life configurations", I mean that it could enumerate them in symbolic form, which would need to be decoded. Translating this symbolic form into an actual realization of the configuration is what I was referring to as producing a "printer" for the computer. --right. Andy Latto has now in several posts, tried to re-say what I already had said in my post. Glad to see great minds think alike. Latto: Thinking about it a bit more, To produce all produceable configurations (those with ancestors arbitrarily far back in time), I don't think the right approach would be "for each configuration, try to find a configuration of gliders that will produce it"; this sounds like a uncomputable task. Instead, we could have the Life Turing machine enumerate all the configurations of gliders, and try them all. --exactly. As I'd already said. Latto: Except that it would have to exclude those configurations that would destroy the computer, and that may be an insoluble problem. --no it is not, as I'd already said; computer can enumerate all configs both synthesizable by, and killable by, gliders. Then as it notices them, it synthesizes and then kills them. Latto: If we only cared about keeping the computer alive for a finite amount if time, the Life-Turing-machine could simulate the glider configuration, and only actually execute it if simulation proved that it didn't destroy the computer in that amount of time. But since we want to produce all of the infinitely many configurations, we want to keep the computer alive forever, and I suspect that the question "Will this life configuration over here ever reach this spot over here?" is uncomputable. --it does not matter that it is uncomputable. We simply enumerate them all. It is like this: we can enumerate and generate all Turing machines that halt, and only those that halt -- even though we cannot decide, given any one, whether it halts. Can you see that? Latto: So I'm not sure an Adam & Eve configuration exists, or at any rate, this angle of attack will succeed in proving that it does. --It's annoying to see this stream of posts from Andy regurgitating my own post rather delayed and imperfectly, but nice to see he's think on the same line, I guess. As I said, a single "genesis seed" configuration exists that will generate every configuration of every finite size that is both synthesizable by and killable by, gliders.