I find it hard to confirm your assessment of my arguments as weak, when your counter-arguments rest on the statistically infinitesimal cases where a fetus develops so abnormally as to have no central nervous system. And the day you can show that sloughed skin cells show any chance of developing into a human being, perhaps you case will be stronger. At the moment, however …

I take it, from your comments, that you are unable to see any distinction between a fetus, a tumor, and sloughed skin cells – and that all three are equally likely to develop into Olympic sprinters? Obviously, a tumor is a case where the mother’s body malfunctions to generate cells, but the cells themselves don’t take off from the mother and develop independently. They may multiply out of control, but that doesn’t mean they’re independent. It is still the mother’s body generating the cells. The fetus, however, does have the ability to develop independently. That’s the biological difference.