I can’t speak for Stoid’s intent any more than you, Scylla, but I took the stem-cell issue to simply be a starting point for the broader discussion.
I’d personally rephrase the question, “At what point is there a rudimentary someone there, rather than something?”
I’d also agree with you and several others here that it’s a blurry process.
I agree that the issue of what the brain is like, at what point in development, is very relevant to the discussion. Whatever I am, take away my brain and all that’s left is a cadaver. I don’t find it defensible that there is a person there before a brain is present. How the development of the human brain during gestation, from a reptilian to a mammalian to a fully human brain, fits into it, I’m personally wrestling with.
I also think there are a couple of other things going on that are worth considering, in deciding how to evaluate what’s there, as opposed to deciding on its personhood.
One is that the embryonic/fetal homo sapiens will, if all goes right, become a person someday, while a full-grown cat will never be anything more than a cat. I personally feel strongly that that potential has to be factored into the equation somehow, though I’m far from sure exactly how to do so. That’s JMHO, though, regardless of its strength.
Another is this: when we first started talking about having children, my wife said, “if I’m unconscious in the delivery room, and the doctors say they’re going to have to choose between saving me and saving the baby, you’d damned well better choose me.”
To which I say, darn tootin’. There’s no way I’m gonna flip a coin, in such a situation, to decide whether it’s the mother or the baby that gets saved, even if the mother wasn’t my wife. And I daresay most people probably feel the same on this.
What this says to me is that, regardless of how God, if there is one, sees the issue, we consider the fetus to have less moral value than an already-born person. Maybe we should see it that way, maybe we shouldn’t. And by how much we value the soon-to-be-born fetus less, I can’t say. But we do.