It makes sense, David. It is an incredibly difficult topic that has tied sentient humans in knots for as long as history. People who have simple answers are to be envied in some degree.

I tend to think of life as binary -- on or off, no half-measures. But I have a very creepy feeling that medical science will soon prove my conjecture is wrong. For instance, I read an article recently which suggested that biologists will soon be able to produce animal flesh for harvesting without bothering to grow a whole organism. Does that pound of ground round without a body have the same veterinary considerations as 'animals'? It's gonna get a lot weirder in our lifetime than we are prepared to deal with.

I think the whole deal with sentience is at least as tricky. You an I agree that reaction to stimuli at the base instinctual level is pretty damned primitive life. We probably also agree that we should treat apes with almost the same consideration as we have for Homo sapiens. Where do the severely mentally retarded or insane humans fit on that scale of apes-to-man? Or how much tissue can we carve from the human being before he is no longer human but still sentient? Or what do we do when we have sentient computers -- maybe in our lifetime?

It's gonna be spooky, weird, and tragic, IMO.