And here we get to one of the biggest questions in the philosophy of artificial intelligence: if something behaves in a way that is indistinguishable from consciousness, is it then conscious? As for the demarkation line for death, that is another controversy altogether. I don't think anyone is saying that it can be answered with complete certainty. Nor is anyone arguing with complete certainty that there is no afterlife. The evidence points towards there being none, but the question can be framed as a non-falsifiable claim, and therefore beyond the realm of science. This doesn't make the existence of an afterlife any more likely, though. It's like Carl Sagan's invisible, silent, heatless dragon in the garage: you can propose the existence of a thing that cannot ever be proved, but that's not a very good reason to believe in that thing.