I am a devout atheist and a scientist. But I understand that religious people live in an alternative reality. Whether that reality is Fox, Ayn Rand, Marx, Medical Marijuana or fundie Islam, the only “rules” I can make are 2. 1. Your reality can not interfere with mine. 2. You can not hurt others. Note these rules are not science. Rather they are, in a sense, themselves religious rules … what Jefferson understood as natural law.But the eternal BUT, abortion is tricky because it depends on WHO is the “other.” If I say that I can decide who is other then I am joining the racists who decided that Jews and American Indians were and are “other.” Governor Stephens of WA state knew he was condemning indigenus Americans to death but regarded that as OK because they were other. If I accept as reality that babies having souls then I am making the same error as Governr Stephens.
So, the only answer is what Jefferson and Voltaie believed in s … natural law. Buddhism teaches that we can discover the Law ( dharma Edward Alan Clark can explain that much better than I) and I agree with that. Judaism has a similar concept .. put forward first by HaLevy and by Maimonides about 1000 years ago. They taught that science supercedes revelation (Torah). So, if I look at laws like the laws in Torah about not hurting others and then look at the science that says identity, (that is the sense that I am me, can not exist until the brain is well developed) under MY LAW I can decide that a conceptus is other. Is this to long winded?
Where this leads me is that the ONLY reason, within science, to impose laws that protect a fetus is a belief in identity that has no scientific basis … what Christians call soul and Buddhists call Samsara (unless Ed corrects me).
This creates two dilemmas .. one you raised. Mothers certainly are not other. Even if there is a soul that exists in the cell ball, the mother’s rights are real too. Compelling her to carry a growth because YOU beleive it has a sould seems wrong.
That leaves the issue of babies that have identity.