Amos, basically you're saying it comes down to "soul", right? (Or something equivalent, anyway.)

I guess my worry with that is the situation covered ad nauseam in fantasy/SF. Because humans are the only fully self-aware species on the planet, we assume that self-aware equals human. If something else comes along that's self-aware, we're not then equipped to deal with it, and things turn to shit. Slavery is the classic example - because black humans weren't thought of as "human", it was thought to be acceptable to treat them like that. By today, we've all made the jump to thinking of "human" as non-skin-colour-dependent, but if we're still stuck in the must-have-two-legs-two-arms-and-be-covered-in-skin definition of sentiency then I think we risk missing something further down the line.

At the risk of sounding like a total SF geek, I can only quote a line from the film DARYL: "A robot becomes human when you can't tell the difference any more". The best summary of the Turing test that I've ever heard. The hypothesis that it'll never happen because computers don't have souls is perfectly legit. At the moment, who knows? The trouble is that if it ever *does* happen then there's a danger of people reversing that logic to say "it can't be happening" in defiance of the evidence.

Me, I'd like to see it happen though, just so the religious nuts can try and work out where the hell it fits in... ;-)

Graham.